| Abramov, P.A., Sokolov, M.N., Hernandez-Molina, R., Vicent, C., Virovets, A.V., Naumov, D.Y., Gili, P., Gonzalez-Platas, J. & Fedin, V.P. ({2010}), "Selective synthesis of triangular cluster oxido-sulfidocomplexes of Mo and W: High yield preparations of [Mo3O2S2(H2O)(9)](4+), [W3O2S2(H2O)(9)](4+), [W2MoO2S2(H2O)(9)](4+) and their derivatization" , INORGANICA CHIMICA ACTA. , OCT 25, {2010}. Vol. {363} ({13}) , pp. {3330-3337}. |
| Abstract: Reaction of [Mo2O2(mu-S)(2)(H2O)(6)](2+) with Mo(CO)(6) or metallic Mo under hydrothermal conditions (140 degrees C, 4 M HCl) gives oxido-sulfido cluster aqua complex [Mo-3(mu(3)-S)(mu-O)(2)(mu-S)(H2O)(9)](4+) (1). Similarly, [W-3(mu(3)-S)(mu-O)(2)(mu-S)(H2O)(9)](4+) (2) is obtained from [W2O2(mu-S)(2)(H2O)(6)](2+) and W(CO)(6). While reaction of [Mo2O2(mu-S)(2)(H2O)(6)](2+) with W(CO)(6) mainly proceeds as simple reduction to give 1, [W2O2(mu-S)(2)(H2O)(6)](2+) with Mo(CO)(6) produces new mixed-metal cluster [W2Mo(mu(3)-S)(mu-O)(2)(mu-S)(H2O)(9)](4+) (3) as main product. From solutions of 1 in HCl supramolecular adduct with cucurbit[6]uril (CB[6]) [Mo3O2S2(H2O)(6)Cl-3](2)CB[6]Cl-2 center dot 18H(2)O (4) was isolated and structurally characterized. The aqua complexes were converted into acetylacetonates [M3O2S2(acac)(3)(py)(3)] PF6 (M-3 = Mo-3, W-3, W2Mo; 5a-c), which were characterized by X-ray single crystal analysis, electrospray ionization mass spectrometry and H-1 NMR spectroscopy. Crystal structure of (H5O2)(Me4N)(4)[W-3(mu(3)-S)(mu(2)-S)(mu(2)-O)(2)(NCS)(9)] (6), obtained from 2, is also reported. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000282677800027,
author = {Abramov, Pavel A. and Sokolov, Maxim N. and Hernandez-Molina, Rita and Vicent, Cristian and Virovets, Alexander V. and Naumov, Dmitry Y. and Gili, Pedro and Gonzalez-Platas, Javier and Fedin, Vladimir P.},
title = {Selective synthesis of triangular cluster oxido-sulfidocomplexes of Mo and W: High yield preparations of [Mo3O2S2(H2O)(9)](4+), [W3O2S2(H2O)(9)](4+), [W2MoO2S2(H2O)(9)](4+) and their derivatization},
journal = {INORGANICA CHIMICA ACTA},
year = {2010},
volume = {363},
number = {13},
pages = {3330-3337},
doi = {{10.1016/j.ica.2010.06.017}}
}
|
| Aceituno, P. & Hernandez-Cabrera, A. ({2008}), "Effect of the shape and duration of excitation pulse on the dynamics of excitons and trions in quantum wells" , PHYSICAL REVIEW B. , SEP, {2008}. Vol. {78} ({11}) |
| Abstract: We have studied the effect of the shape and duration of a photoexcitation pulse on the temporal evolution of excited electrons when they are both free or bounded in excitons and trions. A quantum well with n- and p-type remotely doped regions is considered to get the necessary excess of free electrons or holes. This configuration allows us to study the evolution of both negative and positively charged excitons simultaneously. Calculations have been done using the matrix density formalism to introduce different pulse types. The temporal behavior of the photoluminescence intensity, which is associated with plasma, exciton, and trion, is obtained by means of the two-dimensional density evolution of the different species. |
BibTeX:
@article{ISI:000259690800063,
author = {Aceituno, P. and Hernandez-Cabrera, A.},
title = {Effect of the shape and duration of excitation pulse on the dynamics of excitons and trions in quantum wells},
journal = {PHYSICAL REVIEW B},
year = {2008},
volume = {78},
number = {11},
doi = {{10.1103/PhysRevB.78.115308}}
}
|
| Aceituno, P. & Hernandez-Cabrera, A. ({2005}), "Dynamics of direct-created trions in coupled double quantum wells: Electron-density effects" , JOURNAL OF APPLIED PHYSICS. , JUL 1, {2005}. Vol. {98} ({1}) |
| Abstract: We have studied the coherent dynamics of injected electrons when they are either free or bound in excitons and trions (charged excitons). We have considered a remotely doped asymmetric double quantum well where an excess of free electrons together with direct-created excitons generates trions. We have used the matrix density formalism to analyze the electron dynamics for different concentrations of the three species. Calculations show a significant modification of the free-electron intersublevel oscillations caused by electrons bound in excitons and trions. Based on these calculations we propose a method to detect trions through the emitted electromagnetic radiation or the current density. (c) 2005 American Institute of Physics. |
BibTeX:
@article{ISI:000231062200068,
author = {Aceituno, P and Hernandez-Cabrera, A},
title = {Dynamics of direct-created trions in coupled double quantum wells: Electron-density effects},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2005},
volume = {98},
number = {1},
doi = {{10.1063/1.1949717}}
}
|
| Aceituno, P., Hernandez-Cabrera, A. & Vasko, F. ({2005}), "Intersubband infrared absorption in stepped quantum wells under intense irradiation" , JOURNAL OF PHYSICS-CONDENSED MATTER. , NOV 2, {2005}. Vol. {17} ({43}) , pp. {6925-6933}. |
| Abstract: The effect of an intense THz irradiation on the relative intersubband absorption of electrons in stepped quantum wells of GaAs-GaAlAs is theoretically studied. Analytical expressions for the induced current are obtained by means of the adiabatic and resonant approximations within the matrix density formalism. This method allows one to predict the presence of a marked fine structure on the absorption, together with a shift and broadening of the absorption peaks, when the pump intensity is around the megawatts level. |
BibTeX:
@article{ISI:000233589700016,
author = {Aceituno, P and Hernandez-Cabrera, A and Vasko, FT},
title = {Intersubband infrared absorption in stepped quantum wells under intense irradiation},
journal = {JOURNAL OF PHYSICS-CONDENSED MATTER},
year = {2005},
volume = {17},
number = {43},
pages = {6925-6933},
doi = {{10.1088/0953-08984/17/43/011}}
}
|
| Aceituno, P., Hernandez-Cabrera, A. & Vasko, F.T. ({2008}), "Transverse magnetic mode along THz waveguides with biased superlattices" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {1053-1055}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: We study the propagation of transverse magnetic modes arising from a waveguide consisting on a GaAs-based superlattice located at vacuum-dielectric interface. The transverse mode is generated by the ultrafast intersubband response of the superlattice subjected to a high-frequency electric field. The superlattice is also subjected to a homogeneous bias potential to get a biased superlattice with equipopulated levels. The heterostructure is analyzed through the tight-binding approximation, and considering the level broadening caused by different scattering processes (homogeneous and inhomogeneous broadening mechanisms). We pay special attention to the dispersion relations of the complex dielectric permittivity because of real and imaginary parts of this function play a key role in wide miniband superlattices. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400108,
author = {Aceituno, P. and Hernandez-Cabrera, A. and Vasko, F. T.},
title = {Transverse magnetic mode along THz waveguides with biased superlattices},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {1053-1055},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.10.023}}
}
|
| Alfayate, M.C., Santos, E., Yanes, C., Casanas, N., Vinoly, R., del Mar Romero-Aleman, M. & Monzon-Mayor, M. ({2011}), "Ontogeny of the conus papillaris of the lizard Gallotia galloti and cellular response following transection of the optic nerve: an immunohistochemical and ultrastructural study" , CELL AND TISSUE RESEARCH. , APR, {2011}. Vol. {344} ({1}) , pp. {63-83}. |
| Abstract: Spontaneous regrowth of the axons of retinal ganglion cells (RGC) occurs after unilateral optic nerve transection (ONT) in the lizard Gallotia galloti. We have performed an immunohistochemical and ultrastructural study of the conus papillaris (CP) of this lizard during ontogeny and after ONT in order to characterize its cell subpopulations, innervation and putative blood-brain barrier (BBB) and to evaluate changes occurring throughout regeneration. Proliferating PCNA(+) cells were abundant between embryonic stage 33 (E33) and hatching. From E33, we observed Pax2(+)/GS(+) glial cells in the primitive CP, which became increasingly pigmented and vascularised from E35. Conal astrocytes coexpressing Pax2 with vimentin and/or GFAP were identified from E37-E38. GluT-1(+)/LEA(+)/Pax2(-) endothelial cells (ECs) formed a continuous endothelium with tight junctions and luminal and abluminal microfolds. In adults, the peripheral blood vessels showed a thinner calibre, stronger GluT-1 staining and more abundant microfolds than those of the central CP indicating the higher specialization involved during transport within the former. Occasional pericytes, abundant Pax2(+) pigment cells, LEA(+) microglia/macrophages, unmyelinated Tuj1(+) nerve fibres and SV2(+) synaptic vesicles were also observed in the perivascular zone. After ONT, the expression of GluT-1 and p75(NTR) persisted in ECs, suggesting the preservation/early recovery of the BBB. Relevant ultrastructural alterations were observed at 0.5 months postlesion, although, by 3 months, the CP had recovered the ultrastructure of controls indicating tissue recovery. Abnormal newly formed blood vessels had developed in the CP-optic nerve junction. Thus, the CP is a central nervous system structure whose regenerating capacity might be key for the nutritional support of regenerating RGCs in G. galloti. |
BibTeX:
@article{ISI:000288754300007,
author = {Alfayate, M. C. and Santos, E. and Yanes, C. and Casanas, N. and Vinoly, R. and del Mar Romero-Aleman, Maria and Monzon-Mayor, Maximina},
title = {Ontogeny of the conus papillaris of the lizard Gallotia galloti and cellular response following transection of the optic nerve: an immunohistochemical and ultrastructural study},
journal = {CELL AND TISSUE RESEARCH},
year = {2011},
volume = {344},
number = {1},
pages = {63-83},
doi = {{10.1007/s00441-011-1128-3}}
}
|
| Algarra, A.G., Sokolov, M.N., Gonzalez-Platas, J., Jesus Fernandez-Trujillo, M., Basallote, M.G. & Hernandez-Molina, R. ({2009}), "Synthesis, Reactivity, and Kinetics of Substitution in W3PdSe4 Cuboidal Clusters. A Reexamination of the Kinetics of Substitution of the Related W3S4 Cluster with Thiocyanate" , INORGANIC CHEMISTRY. , APR 20, {2009}. Vol. {48} ({8}) , pp. {3639-3649}. |
| Abstract: The reaction of Pd(dba)(2) (dba = dibenzylideneacetone) with [W3Se4(H2O)(9)](4+) in 2 M HCl gives the cuboidal cluster (W-3(PdCl)Se-4(H2O)(9)](3+), which undergoes edge-to-edge condensation and crystallizes from Hpts solutions as edge-linked double-cubane cluster [W3PdSe4(H2O)(9)(2)](PtS)(8)center dot 18H(2)O (pts(-) = p-toluenesulfonate). The substitution of Cl- by different ligands, including phenylsulfinate PhSO2-, was explored. The phenylsulfinate complex was crystallized as a 2:1 adduct with cucurbit[6]uril (C36H36N24O12), [W-3(Pd(PhSO2)Se-4(H2O)(8.58)Cl-0.42](2)(C36H36N24O12)Cl-5.16 center dot 16.83H(2)O, and its structure was determined by X-ray diffraction. Solution studies indicate that the Pd atom is able to stabilize the pyramidal tautomer of hypophosphorous and phosphorous acid: HP(OH)(2) and P(OH)(3). Kinetic studies were carried out on the reactions with H3PO2 and thiocyanate, which were found to proceed in two and three kinetically resolvable steps, respectively. The kinetic results are discussed in terms of the mechanistic proposals put forward in the literature for related complexes. To gain insight into the details of the substitution kinetics in these kinds of clusters, the reaction of the related [W3S4(H2O)(9)](4+) complex with NCS- has been reexamined, and the results obtained provide for the first time information about the rates of substitution of the whole set of nine-coordinated water molecules. |
BibTeX:
@article{ISI:000265166300037,
author = {Algarra, Andres G. and Sokolov, Maxim N. and Gonzalez-Platas, Javier and Jesus Fernandez-Trujillo, Maria and Basallote, Manuel G. and Hernandez-Molina, Rita},
title = {Synthesis, Reactivity, and Kinetics of Substitution in W3PdSe4 Cuboidal Clusters. A Reexamination of the Kinetics of Substitution of the Related W3S4 Cluster with Thiocyanate},
journal = {INORGANIC CHEMISTRY},
year = {2009},
volume = {48},
number = {8},
pages = {3639-3649},
doi = {{10.1021/ic802150x}}
}
|
| Alonso, D. & Ruiz, A. ({2010}), "Scattering of photons in a two fixed extreme Reissner-Nordstrom black hole system" , In FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS. Vol. {1246} , pp. {45-54}. Note:10th International Symposium on Frontiers of Fundamental and Computational Physics, Perth, AUSTRALIA, NOV 24-26, 2009. |
| Abstract: We study the scattering of light by two fixed extreme Reissner-Nordstrom black holes. We identify the set of unstable periodic orbits of the fractal repeller that describes the chaotic escape dynamics of photons. The main quantities of chaos associated with the repeller are obtained from the analysis of the linear stability of these orbits. The escape rate obtained from the periodic orbit theory is compared with the one obtained from the evolution of statistical ensembles of photons. An analytic estimate of the escape rate in the proximity of a perturbed black hole is also provided. |
BibTeX:
@inproceedings{ISI:000283270500006,
author = {Alonso, Daniel and Ruiz, Antonia},
title = {Scattering of photons in a two fixed extreme Reissner-Nordstrom black hole system},
booktitle = {FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS},
year = {2010},
volume = {1246},
pages = {45-54},
note = {10th International Symposium on Frontiers of Fundamental and Computational Physics, Perth, AUSTRALIA, NOV 24-26, 2009}
}
|
| Alonso, D., Ruiz, A. & Sanchez-Hernandez, M. ({2008}), "Escape of photons from two fixed extreme Reissner-Nordstrom black holes" , PHYSICAL REVIEW D. , NOV, {2008}. Vol. {78} ({10}) |
| Abstract: We study the scattering of light (null geodesics) by two fixed extreme Reissner-Nordstrom black holes, in which the gravitational attraction of their masses is exactly balanced with the electrostatic repulsion of their charges, allowing a static spacetime. We identify the set of unstable periodic orbits that form part of the fractal repeller that completely describes the chaotic escape dynamics of photons. In the framework of periodic orbit theory, the analysis of the linear stability of the unstable periodic orbits is used to obtain the main quantities of chaos that characterize the escape dynamics of the photons scattered by the black holes. In particular, the escape rate that is compared with the result obtained from numerical simulations that consider statistical ensembles of photons. We also analyze the dynamics of photons in the proximity of a perturbed black hole and give an analytic estimate of the escape rate in this system. |
BibTeX:
@article{ISI:000261214100068,
author = {Alonso, Daniel and Ruiz, Antonia and Sanchez-Hernandez, Manuel},
title = {Escape of photons from two fixed extreme Reissner-Nordstrom black holes},
journal = {PHYSICAL REVIEW D},
year = {2008},
volume = {78},
number = {10},
doi = {{10.1103/PhysRevD.78.104024}}
}
|
| Alonso, D. & de Vega, I. ({2010}), "Dynamics of time correlation functions and stochastic quantum trajectories methods in Non-Markovian systems" , In FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS. Vol. {1246} , pp. {88-96}. Note:10th International Symposium on Frontiers of Fundamental and Computational Physics, Perth, AUSTRALIA, NOV 24-26, 2009. |
| Abstract: Open quantum systems are often encountered in many different physical situations. From quantum optics to statistical mechanics, they are fundamental in the understanding of a great variety of different phenomena. Some of the most common examples are the relaxation to equilibrium, the existence of nonequilibrium stationary states, and the dynamics of atoms in interaction with electromagnetic fields. A crucial step in the analysis is to consider the quantum open system and its environment as the two mutually interacting components of a larger isolated system. Thereafter, the so-called Markov approximation is often considered, which consists on assuming that the time scales associated to the dynamics of the quantum open system are larger than those of the environment. It is the interplay of the different time scales associated with the system and the environment what determines the validity of the different approximations made. In this paper we will discuss the dynamics of a open quantum system in contact with a reservoir when the Markov approximation is not valid, and we have to include some non-Markovian or memory effects. |
BibTeX:
@inproceedings{ISI:000283270500010,
author = {Alonso, Daniel and de Vega, Ines},
title = {Dynamics of time correlation functions and stochastic quantum trajectories methods in Non-Markovian systems},
booktitle = {FRONTIERS OF FUNDAMENTAL AND COMPUTATIONAL PHYSICS},
year = {2010},
volume = {1246},
pages = {88-96},
note = {10th International Symposium on Frontiers of Fundamental and Computational Physics, Perth, AUSTRALIA, NOV 24-26, 2009}
}
|
| Alonso, D. & de Vega, I. ({2007}), "Hierarchy of equations of multiple-time correlation functions" , PHYSICAL REVIEW A. , MAY, {2007}. Vol. {75} ({5}) |
| Abstract: In this paper we derive the evolution equations for non-Markovian multiple-time correlation functions of an open quantum system without using any approximation. We find that these equations conform an open hierarchy in which N-time correlation functions are dependent on (N+1)-time correlations. This hierarchy of equations is consistently obtained with two different methods: A first one based on Heisenberg equations of system operators, and a second one based on system propagators. The dependency on higher order correlations, and therefore the open hierarchy structure, only disappears in certain particular cases and when some hypothesis or approximations are considered in the equations. In this paper we consider a perturbative approximation and derive the general evolution equation for N-time correlations. This equation turns to depend only on N-time and lower order correlation functions, conforming a closed hierarchy structure that is useful for computational purposes. |
BibTeX:
@article{ISI:000246890400029,
author = {Alonso, Daniel and de Vega, Ines},
title = {Hierarchy of equations of multiple-time correlation functions},
journal = {PHYSICAL REVIEW A},
year = {2007},
volume = {75},
number = {5},
doi = {{10.1103/PhysRevA.75.052108}}
}
|
| Alonso, D. & de Vega, I. ({2005}), "Multiple-time correlation functions for non-Markovian interaction: Beyond the quantum regression theorem" , PHYSICAL REVIEW LETTERS. , MAY 27, {2005}. Vol. {94} ({20}) |
| Abstract: We derive the dynamical equation of the reduced propagator, an object that evolves state vectors of the system conditioned to the dynamics of its environment, which is not necessarily in the vacuum state at the initial time. Such a reduced propagator is essential to obtain multiple-time correlation functions (MTCFs). We also study the evolution of MTCFs within the weak-coupling limit and show that the quantum regression theorem is, in general, not satisfied. We illustrate the theory in two different cases: first, solving an exact model, and, second, presenting the results of the numerical integration for a system coupled with a thermal environment through a nondiagonal interaction. |
BibTeX:
@article{ISI:000229398100003,
author = {Alonso, D and de Vega, I},
title = {Multiple-time correlation functions for non-Markovian interaction: Beyond the quantum regression theorem},
journal = {PHYSICAL REVIEW LETTERS},
year = {2005},
volume = {94},
number = {20},
doi = {{10.1103/PhysRevLett.94.200403}}
}
|
| Alonso, D., de Vega, I. & Hernandez-Concepcion, E. ({2007}), "Dynamics of fluctuations in non-Markovian systems" , COMPTES RENDUS PHYSIQUE. , JUN-AUG, {2007}. Vol. {8} ({5-6}) , pp. {684-695}. Note:Conference on Work, Dissipation, and Fluctuations in Nonequilibrium Physics, Brussels, BELGIUM, MAR 22-25, 2006. |
| Abstract: The dynamics of multiple time correlation functions (MTCFs) of a system in contact with a non-Markovian environment is relevant in many different contexts. In this article we study the dynamical equations that satisfy MTCFs of a system and how they are used to characterize its fluctuations. The non-Markovian character of the interaction between the system and its environment leads to dynamical equations different from those derived from the Quantum Regression Theorem. We further discuss an stochastic method to compute MTCFs. To illustrate the theory we apply it to the evaluation of the emission spectrum of an atom in contact with a non-Markovian environment. The emission spectrum strongly depends on the way the environment reacts to the absorption of a photon emitted by the atom. |
BibTeX:
@article{ISI:000249366900022,
author = {Alonso, Daniel and de Vega, Ines and Hernandez-Concepcion, Ethel},
title = {Dynamics of fluctuations in non-Markovian systems},
journal = {COMPTES RENDUS PHYSIQUE},
year = {2007},
volume = {8},
number = {5-6},
pages = {684-695},
note = {Conference on Work, Dissipation, and Fluctuations in Nonequilibrium Physics, Brussels, BELGIUM, MAR 22-25, 2006},
doi = {{10.1016/j.crhy.2007.05.019}}
}
|
| Altomare, A., Caliandro, R., Camalli, M., Cuocci, C., Giacovazzo, C., Moliterni, A., Rizzi, R., Spagna, R. & Gonzalez-Platas, J. ({2004}), "Towards EXPO2005" , ZEITSCHRIFT FUR KRISTALLOGRAPHIE. Vol. {219} ({12}) , pp. {833-837}. |
| Abstract: New procedures have been introduced in EXPO2004 (Altomare. A.. Caliandro, R., Camalli, M., Cuocci, C., da Silva, I., Giacovazzo, C., Moliterni, A. G. G. & Rizzi, R., J. Appl. Cryst. Submitted) aiming at making the solution process more straightforward, particularly for cases very resistant to the ab-initio approach. |
BibTeX:
@article{ISI:000226414200009,
author = {Altomare, A and Caliandro, R and Camalli, M and Cuocci, C and Giacovazzo, C and Moliterni, AGG and Rizzi, R and Spagna, R and Gonzalez-Platas, J},
title = {Towards EXPO2005},
journal = {ZEITSCHRIFT FUR KRISTALLOGRAPHIE},
year = {2004},
volume = {219},
number = {12},
pages = {833-837}
}
|
| Alvira, E. ({2010}), "Capacity of small molecules to form beta-cyclodextrin inclusion complexes" , SUPRAMOLECULAR CHEMISTRY. Vol. {22} ({3}) , pp. {156-162}. |
| Abstract: The mobility of atoms and cyclic or spherical guest molecules inside and around beta-cyclodextrin (beta-CD) is analysed, along with the influence of temperature on inclusion complex formation, by means of a molecular dynamics simulation at constant temperature. The intermolecular energy is modelled by a Lennard-Jones potential and a continuum description of the cavity walls. The potential energy parameter sigma principally determines the mobility of the guest inside the cavity in the CD, the preferred position and the probability of forming an inclusion complex, while the parameter 1 is responsible for the guest staying inside or exiting from the cavity after the inclusion time. The probability of entering increases with the temperature of the process. |
BibTeX:
@article{ISI:000274589700003,
author = {Alvira, E.},
title = {Capacity of small molecules to form beta-cyclodextrin inclusion complexes},
journal = {SUPRAMOLECULAR CHEMISTRY},
year = {2010},
volume = {22},
number = {3},
pages = {156-162},
doi = {{10.1080/10610270902980630}}
}
|
| Alvira, E. ({2009}), "Mobility of linear molecules inside and around -cyclodextrin" , MOLECULAR PHYSICS. Vol. {107} ({16}) , pp. {1697-1704}. |
| Abstract: To analyse the mobility of linear guest molecules inside and around -cyclodextrin, as well as their capacity to form inclusion complexes, a molecular dynamics simulation was carried out at constant temperature. Molecules with length [image omitted] angstrom can form inclusion and non-inclusion complexes, depending on the composition and initial position of the guest with respect to the cavity. Linear molecules whose interaction with -cyclodextrin is represented by one pair of values for the Lennard-Jones parameters (sigma,epsilon) and length [image omitted] angstrom can travel inside and outside the cavity, they can even pass through the cyclodextrin forming temporarily inclusion complexes. This inclusion time increases with the molecular length and decreases with the temperature of the simulation. |
BibTeX:
@article{ISI:000267973400009,
author = {Alvira, E.},
title = {Mobility of linear molecules inside and around -cyclodextrin},
journal = {MOLECULAR PHYSICS},
year = {2009},
volume = {107},
number = {16},
pages = {1697-1704},
doi = {{10.1080/00268970903025691}}
}
|
| Alvira, E. ({2007}), "Simulation of the physisorption of linear molecules in beta-cyclodextrin" , JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY. , APR, {2007}. Vol. {57} ({1-4}) , pp. {619-623}. Note:13th International Cyclodextrin Symposium, Torino, ITALY, MAY 14-17, 2006. |
| Abstract: To simulate the interaction energy between beta-cyclodextrin and some linear molecules, a model was constructed from a simple pairwise-additive Lennard-Jones potential combined with a continuum description of the cyclodextrin cavity and of the guest molecule. Depending on the molecular length, one or two pairs of potential parameters are needed to reproduce the main features of the physisorption energy obtained by the all atoms model. From the continuum model, the relationship between the microscopic interaction energy and the macroscopic structural parameters of the molecules can also be established. |
BibTeX:
@article{ISI:000245359500106,
author = {Alvira, E.},
title = {Simulation of the physisorption of linear molecules in beta-cyclodextrin},
journal = {JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY},
year = {2007},
volume = {57},
number = {1-4},
pages = {619-623},
note = {13th International Cyclodextrin Symposium, Torino, ITALY, MAY 14-17, 2006},
doi = {{10.1007/s10847-006-9275-y}}
}
|
| Alvira, E. ({2007}), "A continuum model for van der Waals interaction between beta-cyclodextrin and linear molecules: Part 1" , CHEMICAL PHYSICS LETTERS. , MAY 4, {2007}. Vol. {439} ({1-3}) , pp. {252-257}. |
| Abstract: To simulate the interaction energy between beta-cyclodextrin and linear molecules, a model was constructed from a simple pairwise-additive Lennard-Jones potential combined with a continuum description of the cyclodextrin cavity and the guest molecule. For linear molecules with length L < 6 angstrom, only one pair of potential parameters (sigma, epsilon) were needed to reproduce the main features of the physisorption energy. The variation in the potential energy along the cavity axis was found a well potential where the minimum is deeper as the length or atomic size of the guest molecule increase, in agreement with the results obtained by the all atoms model. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000246609800049,
author = {Alvira, E.},
title = {A continuum model for van der Waals interaction between beta-cyclodextrin and linear molecules: Part 1},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2007},
volume = {439},
number = {1-3},
pages = {252-257},
doi = {{10.1016/j.cplett.2007.03.057}}
}
|
| Alvira, E. ({2007}), "A continuum model for van der Waals interaction between beta-cyclodextrin and linear molecules: Part 2" , CHEMICAL PHYSICS LETTERS. , MAY 4, {2007}. Vol. {439} ({1-3}) , pp. {258-263}. |
| Abstract: To simulate the interaction energy between beta-cyclodextrin and linear molecules, we elaborate a model based on a simple pairwise-additive Lennard-Jones potential and a continuum description of the cyclodextrin cavity and the guest molecule. For linear molecules with length L >= 6 angstrom, two pairs of potential parameters (sigma(1),epsilon(1); sigma(2),epsilon(2)) are needed to reproduce the main features of the physisorption energy obtained by the all atoms model. The penetration potential presents two minima inside the cavity, separated by a potential barrier associated with a rotation of the linear molecule of about 180 with respect to the cavity axis. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000246609800050,
author = {Alvira, E.},
title = {A continuum model for van der Waals interaction between beta-cyclodextrin and linear molecules: Part 2},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2007},
volume = {439},
number = {1-3},
pages = {258-263},
doi = {{10.1016/j.cplett.2007.03.058}}
}
|
| Alvira, E., Mayoral, J.A. & Garcia, J.I. ({2008}), "Enantiodiscrimination of equol in beta-cyclodextrin: an experimental and computational study" , JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY. , FEB, {2008}. Vol. {60} ({1-2}) , pp. {103-113}. |
| Abstract: The interaction between the equol enantiomers and beta -cyclodextrin is studied by molecular mechanics and molecular dynamics calculations. The chromatographic retention order is determined by these theoretical methods and compared with experimental findings. In the molecular mechanics calculations, the simultaneous relaxation of the host and the guest molecules is allowed, both in a vacuum and in aqueous solution. In the molecular dynamics calculations, the interaction energy between each enantiomer and the cavity is determined carrying out a simulation of 12 trajectories with different initial conditions at constant temperature (293 K), and minimising the energy of the structures extracted along the trajectories. To determine the preferential binding site and orientation of each guest molecule, the numerical density of presence in a volume element is calculated and compared with regions of maximum enantioselectivity. The more stable complex predicted in both cases is formed with R-equol, in agreement with experimental results. |
BibTeX:
@article{ISI:000252475000014,
author = {Alvira, Elena and Mayoral, Jose A. and Garcia, Jose I.},
title = {Enantiodiscrimination of equol in beta-cyclodextrin: an experimental and computational study},
journal = {JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY},
year = {2008},
volume = {60},
number = {1-2},
pages = {103-113},
doi = {{10.1007/s10847-007-9358-4}}
}
|
| Aouadi, S., Rodriguez-Hernandez, P., Kassali, K. & Munoz, A. ({2008}), "Lattice dynamics properties of zinc-blende and Nickel arsenide phases of AlP" , PHYSICS LETTERS A. , AUG 4, {2008}. Vol. {372} ({32}) , pp. {5340-5345}. |
| Abstract: Ab initio calculations, based on norm-conserving non-local pseudopotentials and the density functional theory (DFT), have been performed to investigate the behaviour under hydrostatic pressure of the Structural, electronic, elastic and dynamical properties of AlP, in both zinc-blende and nickel arsenide phases. Our calculated structural and electronic properties are in good agreement with previous theoretical and experimental results. The phonon dispersion curves, the elastic constants, Born effective charge, etc., were calculated with the local density approximation and the density functional perturbation theory (DFPT). Our results in the pressure behaviour of the elastic and dynamical properties of both phases are in agreement with the experimental data when available, in other case they can be considered as predictions. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000258254400017,
author = {Aouadi, S. and Rodriguez-Hernandez, P. and Kassali, K. and Munoz, A.},
title = {Lattice dynamics properties of zinc-blende and Nickel arsenide phases of AlP},
journal = {PHYSICS LETTERS A},
year = {2008},
volume = {372},
number = {32},
pages = {5340-5345},
doi = {{10.1016/j.physleta.2008.06.010}}
}
|
| Babu, P., Jang, K.H., Kim, E.S., Shi, L., Seo, H.J., Rivera-Lopez, F., Rodriguez-Mendoza, U.R., Lavin, V., Vijaya, R., Jayasankar, C.K. & Moorthy, L.R. ({2009}), "Spectral investigations on Dy3+-doped transparent oxyfluoride glasses and nanocrystalline glass ceramics" , JOURNAL OF APPLIED PHYSICS. , JAN 1, {2009}. Vol. {105} ({1}) |
| Abstract: Dysprosium-doped oxyfluoride glasses and nanocrystalline glass ceramics have been synthesized and studied by x-ray diffraction, absorption, and visible and near-infrared emission spectra. The samples emit intense white light when populating the 4F(9/2) level with a 451 nm laser light and, from the visible emission spectra, yellow to blue intensity ratios and chromaticity color coordinates have been calculated and their relative variation have been discussed based on the concentration of Dy3+ ions and the heat treatment conditions used to prepare the glass ceramics. Infrared emission has also been observed in glasses and glass ceramics after laser excitation at 800 nm, showing bands at 1.33 and 1.67 mu m, useful for optical amplification in fiber amplifiers. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3021451] |
BibTeX:
@article{ISI:000262534100049,
author = {Babu, P. and Jang, Kyoung Hyuk and Kim, Eun Sik and Shi, Liang and Seo, Hyo Jin and Rivera-Lopez, F. and Rodriguez-Mendoza, U. R. and Lavin, V. and Vijaya, R. and Jayasankar, C. K. and Moorthy, L. Rama},
title = {Spectral investigations on Dy3+-doped transparent oxyfluoride glasses and nanocrystalline glass ceramics},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2009},
volume = {105},
number = {1},
doi = {{10.1063/1.3021451}}
}
|
| Babu, P., Jang, K.H., Kim, E.S., Shi, L., Vijaya, R., Lavin, V., Jayasankar, C.K. & Seo, H.J. ({2010}), "Optical properties and energy transfer of Dy3+-doped transparent oxyfluoride glasses and glass-ceramics" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , FEB 15, {2010}. Vol. {356} ({4-5}) , pp. {236-243}. |
| Abstract: Dysprosium-doped oxyfluoride glasses and nanocrystalline glass-ceramics have been synthesized and studied by X-ray diffraction, transmission electron microscope, optical spectroscopy and time-resolved decay curves measurements. From the absorption spectra, Judd-Ofelt intensity parameters have been obtained and are used to predict radiative properties for the excited states of Dy3+ ions. From the visible emission spectra, yellow to blue intensity ratios have been calculated and their relative variations have been discussed based on the concentration of Dy3+ ions and the heat treatment conditions used to prepare the glass-ceramics. Luminescence decay curves of the F-4(9/2) emitting level are found to be single exponential for 0.01 mol% Dy3+-doped glass and non-exponential for the remaining samples. The nature of energy transfer processes between Dy3+ ions, responsible for the non-exponential behavior of the decay curves, has been analyzed in the frame work of the Inokuti-Hirayama model. Lifetimes of the F-4(9/2) level are found to decrease with the concentration of Dy3+ ions as well as with the time of heat treatment. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000275296000008,
author = {Babu, P. and Jang, Kyoung Hyuk and Kim, Eun Sik and Shi, Liang and Vijaya, R. and Lavin, V. and Jayasankar, C. K. and Seo, Hyo Jin},
title = {Optical properties and energy transfer of Dy3+-doped transparent oxyfluoride glasses and glass-ceramics},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2010},
volume = {356},
number = {4-5},
pages = {236-243},
doi = {{10.1016/j.jnoncrysol.2009.11.010}}
}
|
| Babu, P., Jang, K.H., Rao, C.S., Shi, L., Jayasankar, C.K., Lavin, V. & Seo, H.J. ({2011}), "White light generation in Dy3+-doped oxyfluoride glass and transparent glass-ceramics containing CaF2 nanocrystals" , OPTICS EXPRESS. , JAN 31, {2011}. Vol. {19} ({3}) , pp. {1836-1841}. |
| Abstract: The radiative emission properties of the Dy3+ ions in an oxyfluoride glass and glass-ceramics have been studied for the generation of white light. The x-ray diffraction pattern of the glass-ceramics shows the formation of CaF2 fluorite-type nanocrystals in the glass matrix after a suitable thermal treatment of the precursor glass, whereas time-resolved optical measurements show the incorporation of the Dy3+ ions in the CaF2 nanocrystals. Intense white light has been observed when the samples are excited with 451 nm laser light. From the visible emission spectra, yellow to blue intensity ratios and the chromaticity color coordinates have been determined. All the color coordinates are found to lie in the white light region of the chromaticity color diagram. (C) 2011 Optical Society of America |
BibTeX:
@article{ISI:000286807100018,
author = {Babu, P. and Jang, Kyoung Hyuk and Rao, Ch. Srinivasa and Shi, Liang and Jayasankar, C. K. and Lavin, Victor and Seo, Hyo Jin},
title = {White light generation in Dy3+-doped oxyfluoride glass and transparent glass-ceramics containing CaF2 nanocrystals},
journal = {OPTICS EXPRESS},
year = {2011},
volume = {19},
number = {3},
pages = {1836-1841}
}
|
| Babu, P., Seo, H.J., Jang, K.H., Balakrishnaiah, R., Jayasankar, C.K., Lim, K.-S. & Lavin, V. ({2007}), "Optical spectroscopy, 1.5 mu m emission, and upconversion properties of Er3+-doped metaphosphate laser glasses" , JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS. , SEP, {2007}. Vol. {24} ({9}) , pp. {2218-2228}. |
| Abstract: Metaphosphate glasses doped with five concentrations of Er3+ ions have been investigated through absorption and emission spectra, decay curves, and upconversion measurements. Judd-Ofelt parameters have been evaluated from absorption spectrum of the 1.0 mol. % Er3+-doped glass, which are in turn used to predict radiative properties of some important luminescence levels of Er3+ ions in these glasses. Gain bandwidths of an optical amplifier have been evaluated and are compared with those of reported Er3+:glass systems. Temperature dependence of the 1.5 mu m emission has been studied for the 2.0 mol. % Er3+-doped glass from 13 K to room temperature. Lifetimes of the I-4(3/2) level were measured and are found to decrease with concentration of Er3+ ions after 0.1 mol. Concentration quenching of lifetimes has been analyzed using the theory developed by Auzel et al. [J. Lumin. 94-95, 293 (2001); Opt. Mater. 24, 103 (2003)]. Infrared to visible upconversion was also measured for three concentrations of Er3+-doped metaphosphate glasses with 794 run excitation. A mechanism, involving excited state absorption and energy transfer upconversion, has been proposed to explain the upconversion process. (c) 2007 Optical Society of America. |
BibTeX:
@article{ISI:000249842500027,
author = {Babu, P. and Seo, Hyo Jin and Jang, Kyoung Hyuk and Balakrishnaiah, R. and Jayasankar, C. K. and Lim, Ki-Soo and Lavin, V.},
title = {Optical spectroscopy, 1.5 mu m emission, and upconversion properties of Er3+-doped metaphosphate laser glasses},
journal = {JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS},
year = {2007},
volume = {24},
number = {9},
pages = {2218-2228}
}
|
| Bassioni, G., Delgado, F., Jaeggy, M., Kohler, F., Nogai, S. & Ruiz-Perez, C. ({2005}), "9-Oxabicyclo[3.3.1]nona-2, 6-diene. Short access and allylic bromination" , ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES. , NOV, {2005}. Vol. {60} ({11}) , pp. {1143-1148}. |
| Abstract: 9-Oxabicyclo[3.3.1]nona-2, 6-diene (3) has been synthesized from cycloocta-1, 5-diene in two steps in an overall yield of 88 The dihedral-angle dependence of its H-1 solution NMR data and the double signal set of its C-13 CP MAS NMR spectrum correspond to the results of the single crystal structure analysis. Reaction of 3 with N-bromosuccinimide in the presence of sodium peroxodisulfate or benzoylperoxide has led in good yield to a dibromo derivative 4, and a tribromo derivative 5, respectively. Compounds 4 and 5 feature two allylic bromine substituents, while an additional vinylic bromine atom is present in 5. According to a single crystal structure study the lattice of 4 consists of pairs of enantiomers similar to those found in the case of 3. |
BibTeX:
@article{ISI:000233917400006,
author = {Bassioni, G and Delgado, FS and Jaeggy, M and Kohler, FH and Nogai, S and Ruiz-Perez, C},
title = {9-Oxabicyclo[3.3.1]nona-2, 6-diene. Short access and allylic bromination},
journal = {ZEITSCHRIFT FUR NATURFORSCHUNG SECTION B-A JOURNAL OF CHEMICAL SCIENCES},
year = {2005},
volume = {60},
number = {11},
pages = {1143-1148}
}
|
| Belmar, J., Jimenez, C., Ruiz-Perez, C., Delgado, F.S. & Baggio, R. ({2006}), "A unique tautomer of 1-n-hexyl-3-phenyl-1H-pyrazol-5-ol" , ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS. , OCT, {2006}. Vol. {62} ({Part 10}) , pp. {O599-O601}. |
| Abstract: In the title compound, C15H20N2O, the bond distances and angles are consistent with the presence of the hydroxy tautomer. This tautomer was unambiguously determined by the clear presence of a H atom bonded to oxygen, as well as the total absence of any residual electron density around the N atom in the heterocycle, thus precluding any possibility of desmotropism. |
BibTeX:
@article{ISI:000241002000023,
author = {Belmar, Julio and Jimenez, Claudio and Ruiz-Perez, C. and Delgado, F. S. and Baggio, Ricardo},
title = {A unique tautomer of 1-n-hexyl-3-phenyl-1H-pyrazol-5-ol},
journal = {ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS},
year = {2006},
volume = {62},
number = {Part 10},
pages = {O599-O601},
doi = {{10.1107/S0108270106032926}}
}
|
| Boudjerda, A., Zater, H., Benayache, S., Chalchat, J.-C., Gonzalez-Platas, J., Leon, F., Brouard, I., Bermejo, J. & Benayache, F. ({2008}), "A new guaianolide and other constituents from Achillea ligustica" , BIOCHEMICAL SYSTEMATICS AND ECOLOGY. , MAY-JUN, {2008}. Vol. {36} ({5-6}) , pp. {461-466}. |
BibTeX:
@article{ISI:000255793000023,
author = {Boudjerda, Azzedine and Zater, Hanene and Benayache, Samir and Chalchat, Jean-Claude and Gonzalez-Platas, Javier and Leon, Francisco and Brouard, Ignacio and Bermejo, Jaime and Benayache, Fadila},
title = {A new guaianolide and other constituents from Achillea ligustica},
journal = {BIOCHEMICAL SYSTEMATICS AND ECOLOGY},
year = {2008},
volume = {36},
number = {5-6},
pages = {461-466},
doi = {{10.1016/j.bse.2007.11.006}}
}
|
| Branzea, D.G., Guerri, A., Fabelo, O., Ruiz-Perez, C., Chamoreau, L.-M., Sangregorio, C., Caneschi, A. & Andruh, M. ({2008}), "Heterobinuclear complexes as tectons in designing coordination polymers" , CRYSTAL GROWTH & DESIGN. , MAR, {2008}. Vol. {8} ({3}) , pp. {941-949}. |
| Abstract: Four new 1D coordination polymers have been constructed from [(LCuMII)-M-II] nodes connected by various spacers-the dianion of pyrazole-3,5-dicarboxylic acid (pzdc(2-)), the trianion of trimesic acid (trim(3-)), the tetracyanonickelate(II) anion ([Ni(CN)(4)](2-)), and the dicyanamide anion (dca(-)) [M-II = Mn-II, Co-II, and L2- is the dianion of the Schiff-base resulting from the 2:1 condensation of 3-methoxysalicylaldehyde with 1,3-propanediamine, L2- = N,N'-propylene-bis-(3-methoxysalycilideneiminato)]: [LCuMn(pzdc)(CH3OH)(H2O)]center dot H2O (1), [LCuMn(trim)(2/3)(CH(3)oH)(2/3)(H2O)(1/3)]center dot 0.66(H2O)center dot 0.66(CH3OH) (2), [LCuCo(dca)(2)] (3), and [LCu(CH3OH)(H2O)Mn(NC)(2)Ni(CN)(2)]center dot(H2O)(CH3CN) (4). The fifth compound, [CuLKLCu Ag(CN)(2)] (5), was obtained by reacting [CuL] with K[Ag(CN)(2)]. The magnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic Cu-II-Mn-II intranode interactions (1, J = -48.9 cm(-1); 2, J = -64.7 cm(-1); and 4, J = -60.4 cm(-1); H = -JS(Mn)S(Cu)), as well as weak internodes antiferromagnetic interactions (for compounds 1 and 4). In the case of 2, a weak ferromagnetic internode interaction occurs through the spin polarization mechanism. |
BibTeX:
@article{ISI:000253800200035,
author = {Branzea, Diana G. and Guerri, Annalisa and Fabelo, Oscar and Ruiz-Perez, Catalina and Chamoreau, Lise-Marie and Sangregorio, Claudio and Caneschi, Andrea and Andruh, Marius},
title = {Heterobinuclear complexes as tectons in designing coordination polymers},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2008},
volume = {8},
number = {3},
pages = {941-949},
doi = {{10.1021/cg700846x}}
}
|
| Brouard, S. & Martinez, R. ({2011}), "Cavity-mediated entanglement between distant atoms: Effect of spatial dispersion" , PHYSICS LETTERS A. , APR 11, {2011}. Vol. {375} ({15}) , pp. {1640-1645}. |
| Abstract: The decoherence effect of spatial atomic dispersion on entangled states prepared between two non-interacting atoms that pass through a resonant electromagnetic cavity is studied in detail. Entanglement is shown to oscillate with the atom-field interaction time with an amplitude that decays due to inhomogeneous coupling strength. An upper bound for the entanglement that can be obtained using this procedure is introduced and evaluated numerically for different sets of system parameters. This magnitude depends solely on the overlap between atomic wavefunctions evolved according to two different atom-field interactions. Analytical expressions for the associated decay rate are obtained under different approximations. (C) 2011 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000289449900005,
author = {Brouard, S. and Martinez, R.},
title = {Cavity-mediated entanglement between distant atoms: Effect of spatial dispersion},
journal = {PHYSICS LETTERS A},
year = {2011},
volume = {375},
number = {15},
pages = {1640-1645},
doi = {{10.1016/j.physleta.2011.03.004}}
}
|
| Brouard, S. & Plata, J. ({2005}), "Dissociation of ultracold molecules via Feshbach resonances: The effect of magnetic-field fluctuations" , PHYSICAL REVIEW A. , AUG, {2005}. Vol. {72} ({2}) |
| Abstract: The effect of random magnetic fields on the dissociation of ultracold molecules with Feshbach resonances is studied analytically. The dissociation spectrum and the evolution of the molecule fraction are obtained for a general form of the magnetic-field ramp and different noise properties relevant to standard experimental conditions. The results uncover the robustness against noise of some characteristics of the dissociation process, in particular, of the dependence of the mean atomic kinetic energy on the system parameters. Implications for the applicability of a method proposed to determine the width of the Feshbach resonances from the measurement of the dissociation spectrum are analyzed. Moreover, we discuss how the presence of fluctuations can affect the use of particular ramp shapes to tailor the properties of the generated atomic distribution. |
BibTeX:
@article{ISI:000231564200171,
author = {Brouard, S and Plata, J},
title = {Dissociation of ultracold molecules via Feshbach resonances: The effect of magnetic-field fluctuations},
journal = {PHYSICAL REVIEW A},
year = {2005},
volume = {72},
number = {2},
doi = {{10.1103/PhysRevA.72.023620}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Cano, J., Pasan, J., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2009}), "Dinuclear and two- and three-dimensional gadolinium(III) complexes with mono- and dicarboxylate ligands: synthesis, structure and magnetic properties" , CRYSTENGCOMM. Vol. {11} ({10}) , pp. {2131-2142}. |
| Abstract: Three new gadolinium(III) complexes with carboxylate ligands of formula [Gd-2(ac)(6)(H2O)(4)]center dot 2H(2)O (1), [Gd-2(ac)(2)(fum)(2)(H2O)(4)](n) (2) and [Gd-2(ox)(fum)(2)(H2O)(4)](n)center dot 4nH(2)O (3) (ac = acetate, fum = fumarate and ox oxalate) have been prepared and their structures determined by X-ray diffraction on single crystals. The structure of 1 is made up of discrete centrosymmetric di-mu-oxo( carboxylate acetate) digadolinium( III) units with an intramolecular Gd center dot center dot center dot Gd separation of 4.1589(3) angstrom. Each gadolinium atom in 1 is nine-coordinated with two water molecules and seven carboxylate-oxygen atoms from four acetate ligands building a monocapped square antiprism environment. Compound 2 exhibits a sheet-like structure, the repeating intralayer motif being a rectangle of di-m-oxo( carboxylate acetate) digadolinium(III) units [Gd center dot center dot center dot Gd separation of 3.8659(10) angstrom] where the edges are defined by bridging bis-bidentate and tetrakis-monodentate fumarate groups. Each gadolinium atom in 2 is nine-coordinated with two water molecules and seven carboxylate oxygens from two acetate and three fumarate ligands building a distorted monocapped square antiprism. Compound 3 has a three-dimensional structure where chains of double oxo(carboxylate fumarate)-bridged gadolinium( III) ions are interlinked by bis-bidentate fumarate to afford layers which are further interconnected through bis-bidentate oxalate ligands. The corresponding values of the Gd center dot center dot center dot Gd separation are 4.5816(1), 8.2292(2) and 6.2989(1) A. Each gadolinium atom in 3 is ten-coordinated with two water molecules and eight oxygen atoms from four fumarate ligands and one oxalate group building a distorted bicapped square antiprism. Variable-temperature magnetic susceptibility measurements show the occurrence of weak but significant ferro- (1 and 3) and antiferromagnetic (2) interactions through the double oxo(carboxylate acetate) (1 and 2), double syn-syn carboxylate fumarate (2) and double oxo( carboxylate fumarate) and bis-bidentate oxalate (3) bridges. Monte Carlo calculations were performed in the case of 3 to simulate its magnetic data and to substantiate the best-fit values of the magnetic couplings through the different exchange pathways involved. |
BibTeX:
@article{ISI:000269799400017,
author = {Canadillas-Delgado, Laura and Fabelo, Oscar and Cano, Joan and Pasan, Jorge and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Dinuclear and two- and three-dimensional gadolinium(III) complexes with mono- and dicarboxylate ligands: synthesis, structure and magnetic properties},
journal = {CRYSTENGCOMM},
year = {2009},
volume = {11},
number = {10},
pages = {2131-2142},
doi = {{10.1039/b904764f}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Pasan, J., Delgado, F.S., Deniz, M., Septulveda, E., Laz, M.-M., Julve, M. & Ruiz-Perez, C. ({2008}), "Crystal engineering of complexes of propane-1,2,3-tricarboxylic acid (H(3)tca) with lanthanide(III) cations" , CRYSTAL GROWTH & DESIGN. , APR, {2008}. Vol. {8} ({4}) , pp. {1313-1318}. |
| Abstract: The knowledge of the one-synthon based supramolecular network of the propane-1,2,3-tricarboxylic acid (H(3)tca), commonly referred to as tricarballylic acid (1), induced us to look for new architectures of tricarballylate-containing lanthanide(III) cations having in mind that the structure of the complex [Ce(tca)(H2O)(2)](n) is the only reported example of this type of compounds. Three novel complexes of formulas [Gd(tca)(H2O)(3)](n)center dot nH(2)O (2), [Eu(tca)(H2O)(3)](n)center dot nH(2)O (3), and [La-2(tca)(2)(H2O)(5)](n)center dot 4nH(2)O (4) have been synthesized, and their structures have been determined by X-ray diffraction on single crytals. 2 and 3 are isomorphous compounds. They exhibit a layered structure where the lanthanide atoms are nine-coordinated with three water molecules and six carboxylate-oxygen atoms building a monocapped. square antiprism surrounding and the tca ligands adopting a tris-bidentate coordination mode. 4 has a three-dimensional structure where two 10-coordinated, crystallographically independent lanthanum atoms [La(1) and La(2)] occur with three/two [La(1)/La(2)] water molecules and seven/eight [La(1)/La(2)] carboxylate-oxygens describing bicapped square antiprism surroundings. Two different tca groups are present in 4 both having in common the tris-bidentate coordination mode but acting in addition as monodentate and bis-monodentate ligands through one and two carboxylate groups, respectively. |
BibTeX:
@article{ISI:000254649300041,
author = {Canadillas-Delgado, Laura and Fabelo, Oscar and Pasan, Jorge and Delgado, Fernando S. and Deniz, Mariadel and Septulveda, Eliezer and Laz, Maria-Milagros and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Crystal engineering of complexes of propane-1,2,3-tricarboxylic acid (H(3)tca) with lanthanide(III) cations},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2008},
volume = {8},
number = {4},
pages = {1313-1318},
doi = {{10.1021/cg7010925}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Pasan, J., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2010}), "Intramolecular ferro- and antiferromagnetic interactions in oxo-carboxylate bridged digadolinium(III) complexes" , DALTON TRANSACTIONS. Vol. {39} ({31}) , pp. {7286-7293}. |
| Abstract: Two new digadolinium(III) complexes with monocarboxylate ligands, [Gd-2(pac)(6)(H2O)(4)] (1) and [Gd-2(tpac)(6)(H2O)(4)] (2) (Hpac = pentanoic acid and Htpac = 3-thiopheneacetic acid), have been prepared and their structures determined by X-ray diffraction on single crystals. Their structures consist of neutral and isolated digadolinium(III) units, containing six monocarboxylate ligands and four coordinated water molecules, the bridging skeleton being built by a mu O(1):kappa O-2(1)O(2) framework. This structural pattern has already been observed in the parent acetate-containing compound [Gd-2(ac)(6)(H2O)(4)]center dot 4H(2)O (3) whose structure and magnetic properties were reported elsewhere (L. Canadillas-Delgado, O. Fabelo, J. Cano, J. Pasan, F. S. Delgado, M. Julve, F. Lloret and C. Ruiz-Perez, CrystEngComm, 2009, 11, 2131). Each gadolinium(III) ion in 1 and 2 is nine-coordinated with seven carboxylate-oxygen atoms from four pac (1)/tpac (2) ligands and two water molecules (1 and 2) building a distorted monocapped square antiprism. The values of the intramolecular gadolinium-gadolinium separation are 4.1215(5) (1), 4.1255(6) (2) and 4.1589(3) angstrom (3) and those of the angle at the oxo-carboxylate bridge (theta) are 113.16(13) (1), 112.5(2) (2) and 115.47(7)degrees (3). Magnetic susceptibility measurements in the temperature range 1.9-300 K reveal the occurrence of a weak intramolecular antiferromagnetic interaction [J = -0.032(1) (1) and -0.012(1) cm(-1) (2), the Hamiltonian being defined as (H) over cap = -J (S) over cap (A)center dot(S) over cap (B)] in contrast with the intramolecular ferromagnetic coupling which occurs in 3 (J = +0.031(1) cm(-1)). The magneto-structural data of 1-3 show the relevance of the geometrical parameters at the mu O(1):kappa O-2(1)O(2) bridge on the nature of the magnetic coupling between two gadolinium(III) ions. |
BibTeX:
@article{ISI:000280527300015,
author = {Canadillas-Delgado, Laura and Fabelo, Oscar and Pasan, Jorge and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Intramolecular ferro- and antiferromagnetic interactions in oxo-carboxylate bridged digadolinium(III) complexes},
journal = {DALTON TRANSACTIONS},
year = {2010},
volume = {39},
number = {31},
pages = {7286-7293},
doi = {{10.1039/b920156d}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Pasan, J., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2007}), "Unusual (mu-aqua)bis(mu-carboxylate) bridge in homometallic M(II) (M = mn, co and ni) two-dimensional compounds based on the 1,2,3,4-butanetetracarboxylic acid: Synthesis, structure, and magnetic properties" , INORGANIC CHEMISTRY. , SEP 3, {2007}. Vol. {46} ({18}) , pp. {7458-7465}. |
| Abstract: The first coordination compounds of 1,2,3,4-butanetetracarboxylate anion (butca(4-)) of the formula [M-2(butca)(H2O)(5)](n)center dot 2nH(2)O [M = Mn(II) (1), Co(II) (2), and Ni(II) (3)] were prepared and their X-ray crystal structures and magnetic properties investigated. The three complexes have a very similar two-dimensional structure which consists of (4,4) networks, 1 and 2 being isostructural. The tetracarboxylate ligand acts as a 4-fold connector leading to two-dimensional (4,4) networks of metal atoms, this topology being possible because of its planar conformation. The nodes of these networks are formed by dinuclear motifs which exhibit the unusual (mu-aqua)bis(mu-carboxylate) bridging unit which is analogous to that observed in some molecules of biological interest. The variable-temperature magnetic susceptibility measurements of 1-3 show that 1 and 2 are antiferromagnetically coupled systems whereas 3 exhibits a ferromagnetic behavior. The analysis of the magnetic data of 1-3 through a simple dinuclear model allowed the determination of the values of the magnetic coupling (J) -3.6 (1), -1.2 (2), and +1.47 cm(-1) (3) with the Hamiltonian being defined as H = -JS(A)center dot S-B. The countercomplementarity between the two bridges (aqua and syn-syn carboxylate) accounts for the trend exhibited by the values of the magnetic coupling in this family. |
BibTeX:
@article{ISI:000248984500035,
author = {Canadillas-Delgado, Laura and Fabelo, Oscar and Pasan, Jorge and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Unusual (mu-aqua)bis(mu-carboxylate) bridge in homometallic M(II) (M = mn, co and ni) two-dimensional compounds based on the 1,2,3,4-butanetetracarboxylic acid: Synthesis, structure, and magnetic properties},
journal = {INORGANIC CHEMISTRY},
year = {2007},
volume = {46},
number = {18},
pages = {7458-7465},
doi = {{10.1021/ic7006765}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Pasan, J., Julve, M., Lloret, F. & Ruiz-Perez, C. ({2010}), "All-cis-1,2,3,4,5,6-cyclohexanehexacarboxylate two-dimensional gadolinium(III) complexes: Synthesis, X-ray crystal structure and magnetic properties" , POLYHEDRON. , JAN 13, {2010}. Vol. {29} ({1, Sp. Iss. SI}) , pp. {188-195}. |
| Abstract: The first gadolinium(III) complexes with the trideprotonated form of the 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (H(3)clhexl(3-)) of formulae [Gd(H(3)clhex)(H2O)(4)](n)center dot 3nH(2)O (1) and [Gd(H(3)clhex)(H2O)(4)](n)center dot 6nH(2)O (2) have been prepared through the gel technique and their structures determined by single crystal X-ray diffraction. The structure of 1 is made up of 6(3) honey-comb layers which are generated by [Gd(H2O)(4)](3+) cations and H(3)clhex(3-) anions acting as three-fold nodes and three-fold connectors, respectively. The structure of 2 consists of a [4(4), 6(2)] two-dimensional network extended in the ac plane where the H(3)clhex(-3) groups act as four-fold connectors and the [Gd(H2O)(4)](3+) units as four-fold nodes. Compound 1 crystallises in a non-centrosymmetric space group P2(1). Its absolute structure could be determined reliably, indicating the spontaneous resolution of a homochiral crystal and the freezing of one of the conformations of the all-cis H(3)clhex(-3) ligand. Compound 2 crystallises in the P2(1)/n space group, the presence of an inversion centre making both conformations to occur. 1 and 2 are different solvates of the same system, the latter one synthesised under a higher pH value of the gel than the former. The investigation of the magnetic properties of 1 and 2 in the temperature range 1.9-300 K reveals a Curie law behaviour for the two Compounds. (C) 2009 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000274204300027,
author = {Canadillas-Delgado, Laura and Fabelo, Oscar and Pasan, Jorge and Julve, Miguel and Lloret, Francesc and Ruiz-Perez, Catalina},
title = {All-cis-1,2,3,4,5,6-cyclohexanehexacarboxylate two-dimensional gadolinium(III) complexes: Synthesis, X-ray crystal structure and magnetic properties},
journal = {POLYHEDRON},
year = {2010},
volume = {29},
number = {1, Sp. Iss. SI},
pages = {188-195},
doi = {{10.1016/j.poly.2009.06.068}}
}
|
| Canadillas-Delgado, L., Fabelo, O., Ruiz-Perez, C., Delgado, F., Julve, M., Hernandez-Molina, M., Laz, M. & Lorenzo-Luis, P. ({2006}), "Zeolite-like nanoporous gadolinium complexes incorporating alkaline cations" , CRYSTAL GROWTH & DESIGN. , JAN, {2006}. Vol. {6} ({1}) , pp. {87-93}. |
| Abstract: In this article, we describe the synthesis and single-crystal X-ray structural studies of two new lanthanide complexes of formula [M(I)Ln(III)(bta)(H2O)(3)]center dot nH(2)O, (M = Na (1), K (2); Ln = Gd; H(4)bta = 1,2,4,5-benzenetetracarboxylic acid) to check the ability of rare earth ions to lead to high-dimensional materials. The crystal structures of 1 and 2 can be described as a succession of layers made up of chains with regular alternation of pairs of Gd3+ and Na+ or K+ ions that are connected by bta(4-) groups. Both structures contain a nine-coordinated gadolinium(Ill) cation ion and fully deprotonated bta(4-) anion. However, the alkaline cations exhibit different coordination numbers, seven (Na+) and nine (K+). The structures accommodate crystallization and coordination water molecules, and it was observed that the water molecules have a significant influence on the coordination geometry and on the overall extended structure. These compounds may be considered as novel nanocomposites of unusual structures within the benzenetetracarboxylate frameworks. |
BibTeX:
@article{ISI:000234723700020,
author = {Canadillas-Delgado, L and Fabelo, O and Ruiz-Perez, C and Delgado, FS and Julve, M and Hernandez-Molina, M and Laz, MM and Lorenzo-Luis, P},
title = {Zeolite-like nanoporous gadolinium complexes incorporating alkaline cations},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2006},
volume = {6},
number = {1},
pages = {87-93},
doi = {{10.1021/cg050170t}}
}
|
| Canadillas-Delgado, L., Martin, T., Fabelo, O., Pasan, J., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2010}), "The Construction of Open Gd-III Metal-Organic Frameworks Based on Methanetriacetic Acid: New Objects with an Old Ligand" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {16} ({13}) , pp. {4037-4047}. |
| Abstract: The preparation, X-ray crystallography and magnetic investigation of the first examples of methanetriacetate (mta)-containing lanthanide(III) complexes of formulae [Gd(mta)(H2O)(3)](n)center dot 4(n)H(2)O (1) [Gd(mta)(H2O)(3)](n)center dot 2nH(2)O (2) and [Gd-2(mta)(2)(H2O)(2)](n)center dot 2nH(2)O (3) are described herein. This tripodal ligand promotes the formation of 6(3) networks; thus 1 consists of a honeycomb structure, whereas in 2 two of these layers are condensed to form a rare five-connected two-dimensional (4(8)6(2)) network. Compound 3 can be seen as an aggregation of 6(3) layers leading to a three-dimensional (6,6)-connected binodal (4(12)6(3))(4(9)6(6))-nia net, in which the gadolinium(III) ions and the mta ligands act as octahedral and as trigonal prismatic nodes, respectively. The magnetic properties of 1-3 were investigated in the temperature range 1.9-300 K. A close fit to the Curie law (1) and weak either antiferro- [J= -0.0063(1) cm(-1) (2)] or ferromagnetic [J=+0.0264(6) cm(-1) (3)] interactions between the GdIn ions are observed; the different exchange pathways involved [extended tris-bidentate mta (1) and mu-O(1);kappa O-2(1),O(2) (2 and 3) plus single syn-syn carboxylate-mta (3)] accounting for these magnetic features. The nature and magnitude of the magnetic interactions, between the Gdul ions in 1-3, agree with the small amount of data existing in the literature for these kind of bridges. |
BibTeX:
@article{ISI:000276735900021,
author = {Canadillas-Delgado, Laura and Martin, Tomas and Fabelo, Oscar and Pasan, Jorge and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {The Construction of Open Gd-III Metal-Organic Frameworks Based on Methanetriacetic Acid: New Objects with an Old Ligand},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2010},
volume = {16},
number = {13},
pages = {4037-4047},
doi = {{10.1002/chem.200903053}}
}
|
| Canadillas-Delgado, L., Pasan, J., Fabelo, O., Hernandez-Molina, M., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2006}), "Two- and three-dimensional networks of gadolinium(III) with dicarboxylate ligands: Synthesis, crystal structure, and magnetic properties" , INORGANIC CHEMISTRY. , DEC 25, {2006}. Vol. {45} ({26}) , pp. {10585-10594}. |
| Abstract: Four gadolinium(III) complexes with dicarboxylate ligands of formulas [Gd-2(mal)(3)(H2O)(5)](n)center dot 2nH(2)O (1), [Gd-2(mal)3( H2O)(6)](n) (2), [NaGd(mal)(ox)(H2O)(3)](n) (3), and [Gd-2(ox)(3)(H2O)(6)](n)center dot 2.5nH(2)O (4) (mal = malonate; ox = oxalate) have been prepared, and their magnetic properties have been investigated as a function of the temperature. The structures of 1-3 have been determined by X-ray diffraction methods. The crystal structure of 4 was already known, and it is made of hexagonal layers of Gd atoms that are bridged by bis-bidentate oxalate. Compound 1 is isostructural with the europium(III) malonate complex [Eu-2(mal)(3)(H2O)(5)](n)center dot 2nH(2)O,(1) whose structure was reported elsewhere. The Gd atoms in 1 define a two-dimensional network where a terminal bidentate and bridging bidentate/bis-monodentate and tris-bidentate coordination modes of malonate occur. Compound 2 has a three-dimensional structure with a structural phase transition at 226 K, which involves a change of the space group from I2Ia to Ia. Although its structure at room temperature was already known, that below 226 K was not. Pairs of Gd atoms with a double oxo-carboxylate bridge occur in both phases, and the main differences between both structures deal with the Gd environment and the H-bond pattern. 3 is also a three-dimensional compound, and it was obtained by reacting Gd(III) ions with malonic acid in a silica gel medium. Oxalic acid results as an oxidized product of the malonic acid, and single crystals of the heteroleptic complex were produced. The Gd atoms in 3 are connected through bisbidentate oxalate and carboxylate-malonate bridges in the anti-anti and anti-syn coordination modes. Compounds 1 and 2 exhibit weak but significant ferromagnetic couplings between the Gd(III) ions through the single (1) and double (2) oxo-carboxylate bridges, whereas antiferromagnetic interactions across the bis-bidentate oxalate account for the overall antiferromagnetic behavior observed in 3 and 4. |
BibTeX:
@article{ISI:000242899400030,
author = {Canadillas-Delgado, Laura and Pasan, Jorge and Fabelo, Oscar and Hernandez-Molina, Maria and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Two- and three-dimensional networks of gadolinium(III) with dicarboxylate ligands: Synthesis, crystal structure, and magnetic properties},
journal = {INORGANIC CHEMISTRY},
year = {2006},
volume = {45},
number = {26},
pages = {10585-10594},
doi = {{10.1021/ic061173d}}
}
|
| Cardona, M., Kremer, R.K., Lauck, R., Siegle, G., Munoz, A. & Romero, A.H. ({2009}), "Electronic, vibrational, and thermodynamic properties of metacinnabar beta-HgS, HgSe, and HgTe" , PHYSICAL REVIEW B. , NOV, {2009}. Vol. {80} ({19}) |
| Abstract: We report ab initio calculations of the electronic band structure and the phonon dispersion relations of the zincblende-type mercury chalcogenides (beta-HgS, HgSe, and HgTe). The latter have been used to evaluate the temperature dependence of the specific heat, which has been compared with experimental data. The electronic band structure of these materials has been confirmed to have an inverted direct gap of the alpha-tin type, which makes HgSe and HgTe semimetallic. For beta-HgS, however, our calculations predict a negative spin-orbit splitting that restores semiconducting properties to the material in spite of the inverted gap. We have calculated the spin-orbit induced linear terms in k, which appear at the Gamma(8) valence bands. We have also investigated the pressure dependence of the crystal structure and the phonons. |
BibTeX:
@article{ISI:000272311000055,
author = {Cardona, M. and Kremer, R. K. and Lauck, R. and Siegle, G. and Munoz, A. and Romero, A. H.},
title = {Electronic, vibrational, and thermodynamic properties of metacinnabar beta-HgS, HgSe, and HgTe},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {80},
number = {19},
doi = {{10.1103/PhysRevB.80.195204}}
}
|
| Cardona, M., Kremer, R.K., Lauck, R., Siegle, G., Munoz, A., Romero, A.H. & Schindler, A. ({2010}), "Electronic, vibrational, and thermodynamic properties of ZnS with zinc-blende and rocksalt structure" , PHYSICAL REVIEW B. , FEB, {2010}. Vol. {81} ({7}) |
| Abstract: We have measured the specific heat of zinc-blende ZnS for several isotopic compositions and over a broad temperature range (3-1100 K). We have compared these results with calculations based on ab initio electronic band structures, performed using both local-density approximation and generalized gradient approximation exchange-correlation functionals. We have compared the lattice dynamics obtained in this manner with experimental data and have calculated the one-phonon and two-phonon densities of states. We have also calculated mode-Gruneisen parameters at a number of high-symmetry points of the Brillouin zone. The electronic part of our calculations has been used to investigate the effect of the 3d core electrons of zinc on the spin-orbit splitting of the top valence bands. The effect of these core electrons on the band structure of the rocksalt modification of ZnS is also discussed. |
BibTeX:
@article{ISI:000274998200062,
author = {Cardona, M. and Kremer, R. K. and Lauck, R. and Siegle, G. and Munoz, A. and Romero, A. H. and Schindler, A.},
title = {Electronic, vibrational, and thermodynamic properties of ZnS with zinc-blende and rocksalt structure},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {7},
doi = {{10.1103/PhysRevB.81.075207}}
}
|
| Cardona, M., Kremer, R.K., Siegle, G., Munoz, A., Romero, A.H. & Schmidt, M. ({2010}), "Electronic and phononic properties of cinnabar: Ab initio calculations and some experimental results" , PHYSICAL REVIEW B. , AUG 30, {2010}. Vol. {82} ({8}) |
| Abstract: We report ab initio calculations of the electronic band structure, the corresponding optical spectra, and the phonon dispersion relations of trigonal alpha-HgS (cinnabar). The calculated dielectric functions are compared with unpublished optical measurements by [Zallen et al. (unpublished)] The phonon dispersion relations are used to calculate the temperature and isotopic mass dependence of the specific heat which has been compared with experimental data obtained on samples with the natural isotope abundances of the elements Hg and S (natural minerals and vapor phase grown samples) and on samples prepared from isotope enriched elements by vapor phase transport. Comparison of the calculated vibrational frequencies with Raman and ir data is also presented. Contrary to the case of cubic beta-HgS (metacinnabar), the spin-orbit splitting of the top valence bands at the Gamma point of the Brillouin zone (Delta 0) is positive, because of a smaller admixture of 5d core electrons of Hg. Calculations of the lattice parameters, and the pressure dependence of Delta 0 and the corresponding direct gap E-0 similar to 2 eV are also presented. The lowest absorption edge is confirmed to be indirect. |
BibTeX:
@article{ISI:000281367200005,
author = {Cardona, M. and Kremer, R. K. and Siegle, G. and Munoz, A. and Romero, A. H. and Schmidt, M.},
title = {Electronic and phononic properties of cinnabar: Ab initio calculations and some experimental results},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {82},
number = {8},
doi = {{10.1103/PhysRevB.82.085210}}
}
|
| Carro, P., Hernandez Creus, A., Munoz, A. & Salvarezza, R.C. ({2010}), "On the Thermodynamic Stability of alpha,omega-Alkanedithiols Self-Assembled Mono layers on Unreconstructed and Reconstructed Au(111)" , LANGMUIR. , JUN 15, {2010}. Vol. {26} ({12}) , pp. {9589-9595}. |
| Abstract: A comparative study on the thermodynamic stability of the lying down (LD) and standing up (SU) phases of alpha,omega-butanedithiol (BDT) on unreconstructed (U) and on reconstructed (R) Au(111) surfaces is presented. The R surface is made of dithiol-Au adatom units. Density functional calculations (DFT) allow the estimation of the adsorption energy of the LD and SU BDT phases on both substrates. Surface free energies based on the DFT calculations show the coverage of the clean Au(111) surface by the ID phase, and the ID to SU phase transition as the chemical potential of the BDT molecule is increased. The LD and SU phases are more stable on R than on U substrates, suggesting that the Au(111) surface should reconstruct upon BDT adsorption. The stability analysis is extended to longer alpha,omega-dithiols. Results reveal that the to SU phase transition is favored as the hydrocarbon chain length of the dithiol molecule is increased. Changes in the hydrogen pressure affect the formation of the ID phase, while they have only minor effects on the LD to SU phase transitions. Our calculations explain the influence of the number of carbon atoms in the hydrocarbon chains, hydrogen pressure and dithiol pressure (or concentration) on dithiol adsorption, and phase transitions. This information is relevant to control the coverage, reactivity, and surface chemistry of the alpha,omega-dithiol self-assembled monolayers on Au surfaces. |
BibTeX:
@article{ISI:000278427600060,
author = {Carro, P. and Hernandez Creus, A. and Munoz, A. and Salvarezza, R. C.},
title = {On the Thermodynamic Stability of alpha,omega-Alkanedithiols Self-Assembled Mono layers on Unreconstructed and Reconstructed Au(111)},
journal = {LANGMUIR},
year = {2010},
volume = {26},
number = {12},
pages = {9589-9595},
doi = {{10.1021/la100167b}}
}
|
| Casanas, N., Monzon-Mayor, M., Romero-Aleman, M.M., Santos, E., Vinoly, R., Alfayate, M.C., Lang, D. & Yanes, C. ({2009}), "IMMUNOHISTOCHEMICAL CHARACTERIZATION OF MULLER GLIAL CELLS DURING THE LIZARD ONTOGENY AND AFTER OPTIC NERVE TRANSECTION" , GLIA. , OCT, {2009}. Vol. {57} ({13, Suppl. S}) , pp. {S154}. Note:9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009. |
BibTeX:
@article{ISI:000270075500632,
author = {Casanas, N. and Monzon-Mayor, M. and Romero-Aleman, M. M. and Santos, E. and Vinoly, R. and Alfayate, M. C. and Lang, D. and Yanes, C.},
title = {IMMUNOHISTOCHEMICAL CHARACTERIZATION OF MULLER GLIAL CELLS DURING THE LIZARD ONTOGENY AND AFTER OPTIC NERVE TRANSECTION},
journal = {GLIA},
year = {2009},
volume = {57},
number = {13, Suppl. S},
pages = {S154},
note = {9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009}
}
|
| del Castillo, J., Mendez-Ramos, J., Yanes, A.C. & Rodriguez, V.D. ({2009}), "Wide colour gamut generated in triply lanthanide doped sol-gel nano-glass-ceramics" , JOURNAL OF NANOPARTICLE RESEARCH. , MAY, {2009}. Vol. {11} ({4}) , pp. {879-884}. |
| Abstract: The generation of a wide colour gamut, based on up-conversion of cheap near-infrared photons into the visible range, is of great importance for general lighting appliances and integrated optical devices. Here, we report for the first time on up-conversion luminescence under infrared excitation at 980 nm in Yb3+-Er3+-Tm3+ triply doped sol-gel derived SiO2-LaF3 based nano-glass-ceramics (SOL-YET), containing LaF3 nanocrystals with a size about 13 nm. Efficient simultaneous up-conversion emission of the three primary colours (blue, green and red) gives rise to a balanced white overall emission. The ratio between up-conversion emission bands can be varied by changing pump power intensity resulting in colour tuneable up-conversion phosphor. |
BibTeX:
@article{ISI:000264838100013,
author = {del-Castillo, J. and Mendez-Ramos, J. and Yanes, A. C. and Rodriguez, V. D.},
title = {Wide colour gamut generated in triply lanthanide doped sol-gel nano-glass-ceramics},
journal = {JOURNAL OF NANOPARTICLE RESEARCH},
year = {2009},
volume = {11},
number = {4},
pages = {879-884},
doi = {{10.1007/s11051-008-9470-4}}
}
|
| del Castillo, J., Mendez-Ramos, J., Yanes, A.C., Velazquez, J.J. & Rodriguez, V.D. ({2008}), "Gain cross-section of 1.06 mu m emission in Nd3+-doped SiO2-LaF3 glass-ceramics prepared by sol-gel method" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , APR 15, {2008}. Vol. {354} ({18}) , pp. {2000-2003}. |
| Abstract: The room temperature near-infrared emission at 1.06 mu m corresponding to the F-4(3/2)-> I-4(11/2) laser transition in Nd3+-doped SiO2-LaF3 transparent glass-ceramics prepared by sol-gel method has been characterized in terms of the product of emission crosssection and fluorescence lifetime. Stimulated emission cross-sections have been calculated from experimental emission spectra using the Fuchtbauer-Ladenburg equation. The precipitation of LaF3 nanocrystals after heat-treatment, confirmed by X-ray diffraction, induces a significant increment of the 1.06 mu m near-infrared emission compared with the as made sample. An enhancement of emission cross-section of about 10% has been achieved with increasing temperature of heat-treatment of the nano-ceramming process from 800 to 1000 degrees C, which is related to the growth of LaF3 nanocrystals. (c) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255504300010,
author = {del-Castillo, J. and Mendez-Ramos, J. and Yanes, A. C. and Velazquez, J. J. and Rodriguez, V. D.},
title = {Gain cross-section of 1.06 mu m emission in Nd3+-doped SiO2-LaF3 glass-ceramics prepared by sol-gel method},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2008},
volume = {354},
number = {18},
pages = {2000-2003},
doi = {{10.1016/j.jnoncrysol.2007.11.009}}
}
|
| del Castillo, J., Rodriguez, V.D., Yanes, A.C. & Mendez-Ramos, J. ({2008}), "Energy transfer from the host to Er3+ dopants in semiconductor SnO2 nanocrystals segregated in sol-gel silica glasses" , JOURNAL OF NANOPARTICLE RESEARCH. , MAR, {2008}. Vol. {10} ({3}) , pp. {499-506}. |
| Abstract: Undoped and Er3+-doped glass-ceramics of composition (100-x)SiO2-xSnO(2), with x = 5 or 10 and with 0.4 or 0.8 mol% of Er3+ ions, were synthesised by thermal treatment of precursor sol-gel glasses. Structural studies were developed by X-Ray Diffraction. Wide band gap SnO2 semiconductor quantum-dots embedded in the insulator SiO2 glass are obtained. The mean radius of the SnO2 nanocrystals, ranging from 2 to 3.2 nm, is comparable to the exciton Bohr radius. The luminescence properties have been analysed as a function of sample composition and thermal treatment. The results show that Er3+ ions are partially partitioned into the nanocrystalline phase. An efficient UV excitation of the Er3+ ions by energy transfer from the SnO2 nanocrystal host is observed. The Er3+ ions located in the SnO2 nanocrystals are selectively excited by this energy transfer mechanism. On the other hand, emission from the Er3+ ions remaining in the silica glassy phase is obtained by direct excitation of these ions. |
BibTeX:
@article{ISI:000252541100013,
author = {del-Castillo, Javier and Rodriguez, V. D. and Yanes, A. C. and Mendez-Ramos, J.},
title = {Energy transfer from the host to Er3+ dopants in semiconductor SnO2 nanocrystals segregated in sol-gel silica glasses},
journal = {JOURNAL OF NANOPARTICLE RESEARCH},
year = {2008},
volume = {10},
number = {3},
pages = {499-506},
doi = {{10.1007/s11051-007-9283-x}}
}
|
| del Castillo, J., Yanes, A.C., Mendez-Ramos, J. & Rodriguez, V.D. ({2009}), "Undoped and Eu3+ Doped In2O3 Quantum-Dots in Transparent Glass-Ceramics" , JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. , AUG, {2009}. Vol. {9} ({8}) , pp. {4834-4838}. |
| Abstract: Nano-structured glass-ceramics comprising In2O3 nanocrystals (quantum dots) in a silica glassy matrix have been synthesized for the first time to our knowledge, by thermal treatment of sol-gel precursor glasses with different concentrations of In2O3. Undoped and Eu3+-doped samples have been obtained and characterized. By means of X-ray Diffraction and Transmission Electron Microscopy analysis, the precipitation of In2O3 cubic crystalline nanoparticles was confirmed. The mean radii of these nanocrystals, from 1 to 4 nm, are comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots. Under interband UV excitation of the nanocrystals, a broad visible emission is observed in the undoped samples. Meanwhile, the Eu3+-doped samples only show emission from these ions which are efficiently excited by energy transfer from the In2O3 nanocrystals. Selective excitation of the Eu3+ ions allow us to discern those remaining in the silica glassy matrix from the ones located in the interface SiO2-In2O3. |
BibTeX:
@article{ISI:000267994100044,
author = {del-Castillo, J. and Yanes, A. C. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Undoped and Eu3+ Doped In2O3 Quantum-Dots in Transparent Glass-Ceramics},
journal = {JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY},
year = {2009},
volume = {9},
number = {8},
pages = {4834-4838},
doi = {{10.1166/jnn.2009.1371}}
}
|
| del Castillo, J., Yanes, A.C., Mendez-Ramos, J. & Rodriguez, V.D. ({2008}), "Luminescence of nanostructured SnO2-SiO2 glass-ceramics prepared by sol-gel method" , JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. , APR, {2008}. Vol. {8} ({4}) , pp. {2143-2146}. |
| Abstract: Nanostructured silica based glass-ceramics samples of composition (100 - x)SiO2-xSnO(2), with x from 1 to 10, have been synthesized by thermal treatment of precursor sol-gel glasses. The average size of the obtained SnO2 nanocrystals, calculated by using the X-ray diffraction, can be predetermined by using well-controlled concentration of tin precursor. The mean radius ranging from 1.6 to 5.5 nm, is comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots in an insulator SiO2 glass. A spectroscopy study in terms of optical absorption and photoluminescence spectra has been carried out as a function of SnO2 concentration. Size-dependent red-shifts of excitation and emission bands, with increasing of tin precursor concentration, point to the quantum confinement effect. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. The band gap increase is in agreement with results, based on the effective mass model. The recombination of conduction band electron with oxygen vacancies is proposed to explain the luminescence red-shift. |
BibTeX:
@article{ISI:000255790400069,
author = {del-Castillo, J. and Yanes, A. C. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Luminescence of nanostructured SnO2-SiO2 glass-ceramics prepared by sol-gel method},
journal = {JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY},
year = {2008},
volume = {8},
number = {4},
pages = {2143-2146},
doi = {{10.1166/jnn.2008.068}}
}
|
| del Castillo, J., Yanes, A.C., Mendez-Ramos, J., Tikhomirov, V.K., Moshchalkov, V.V. & Rodriguez, V.D. ({2010}), "Sol-gel preparation and white up-conversion luminescence in rare-earth doped PbF2 nanocrystals dissolved in silica glass" , JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY. , MAR, {2010}. Vol. {53} ({3}) , pp. {509-514}. |
| Abstract: 89.5(SiO2)10(PbF2)0.5(REF3) silicate glasses have been prepared using room temperature sol-gel processing of Si(OCH2CH3)(4), Pb(CH3COO)(2)center dot 3H(2)O, RE(CH3COO)(3)center dot nH(2)O and trifluoroacetic acid as a fluorinating agent, where RE stands for rare-earth ions, such as Yb3+, Er3+, Ho3+, Tm3+, or combinations of those ions. On heat treatment of these glasses at about 300-400 A degrees C, the rare-earth doped spherical PbF2 nanocrystals precipitate within SiO2 glass matrix providing transparent nano-structured glass-ceramics, while the diameter of the nanocrystals can be set in the range from 5 to 25 nm by varying time and temperature of the heat treatment. The structural and photoluminescence studies confirm the incorporation of rare-earth ions into the PbF2 nanocrystals and white and tuneable colour up-conversion luminescence has been detected in case of Yb3+-Er3+-Tm3+ and Yb3+-Ho3+-Tm3+ co-doped nanocrystals by varying dopant ratio and pump power. |
BibTeX:
@article{ISI:000275161100004,
author = {del-Castillo, J. and Yanes, A. C. and Mendez-Ramos, J. and Tikhomirov, V. K. and Moshchalkov, V. V. and Rodriguez, V. D.},
title = {Sol-gel preparation and white up-conversion luminescence in rare-earth doped PbF2 nanocrystals dissolved in silica glass},
journal = {JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY},
year = {2010},
volume = {53},
number = {3},
pages = {509-514},
doi = {{10.1007/s10971-009-2124-x}}
}
|
| del Castillo, J., Yanes, A.C., Mendez-Ramos, J., Tikhomirov, V.K. & Rodriguez, V.D. ({2009}), "Structure and up-conversion luminescence in sol-gel derived Er3+-Yb3+ co-doped SiO2:PbF2 nano-glass-ceramics" , OPTICAL MATERIALS. , NOV, {2009}. Vol. {32} ({1}) , pp. {104-107}. |
| Abstract: Transparent oxyfluoride nano-glass-ceramics 90(SiO2)10(PbF2) co-doped with 0.3 Yb3+ and 0.1 Er3+ (mol have been prepared by thermal treatment of precursor sol-gel glasses. X-ray diffraction and high resolution transmission electron microscopy analysis pointed out a precipitation of cubic beta-PbF2 nanocrystals of certain diameter in nano-glass-ceramics varying from 10 to 20 nm depending on heat treatment conditions. The incorporation of Yb3+ and Er3+ dopants in these nanocrystals has been confirmed by signatures of luminescence spectroscopy. Up-conversion luminescence pumped at 980 nm has been detected. Colour tuneability of up-conversion luminescence varying pump power has been analyzed in terms of standard chromaticity diagram. This tuneability opens applications for up-conversion phosphors and three-dimensional optical recording. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000271888500021,
author = {del-Castillo, J. and Yanes, A. C. and Mendez-Ramos, J. and Tikhomirov, V. K. and Rodriguez, V. D.},
title = {Structure and up-conversion luminescence in sol-gel derived Er3+-Yb3+ co-doped SiO2:PbF2 nano-glass-ceramics},
journal = {OPTICAL MATERIALS},
year = {2009},
volume = {32},
number = {1},
pages = {104-107},
doi = {{10.1016/j.optmat.2009.06.013}}
}
|
| del Castillo, J., Yanes, A.C., Velazquez, J.J., Mendez-Ramos, J. & Rodriguez, V.D. ({2009}), "Luminescent properties of Eu3+-Tb3+-doped SiO2-SnO2-based nano-glass-ceramics prepared by sol-gel method" , JOURNAL OF ALLOYS AND COMPOUNDS. , APR 3, {2009}. Vol. {473} ({1-2}) , pp. {571-575}. |
| Abstract: Transparent nano-glass-ceramics of composition 95SiO(2)-5SnO(2) mol single doped with 0.4 mol% of Tb3+ and co-doped with 0.4 mol% of Eu3+ and Tb3+ have been obtained by thermal treatment of precursor sol-gel glasses. The segregated SnO2 nanocrystals, precipitated in the insulator SiO2 glass matrix during heat treatment, constitute a wide band gap quantum-dot system with mean radius of nanocrystals around 2.2-2.8 nm, comparable to the bulk exciton Bohr radius. A fraction of the rare earth ions is incorporated to the SnO2 nanocrystals and can be excited by energy transfer from the semiconductor host. The efficiency of this energy transfer process is strongly dependent on the nanocrystal radius in the case of the Tb3+ ions, whereas the dependence is not appreciable in the case of Eu3+ ions. These results can be explained taking into account the variations of the overlap of the SnO2 broad visible emission due to oxygen vacancies with the rare earth excitation spectra. (c) 2008 Elsevier B.V. All rights reserved |
BibTeX:
@article{ISI:000264890500116,
author = {del-Castillo, J. and Yanes, A. C. and Velazquez, J. J. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Luminescent properties of Eu3+-Tb3+-doped SiO2-SnO2-based nano-glass-ceramics prepared by sol-gel method},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2009},
volume = {473},
number = {1-2},
pages = {571-575},
doi = {{10.1016/j.jallcom.2008.06.048}}
}
|
| Clemente-Leon, M., Coronado, E., Carmen Gimenez-Lopez, M., Soriano-Portillo, A., Waerenborgh, J.C., Delgado, F.S. & Ruiz-Perez, C. ({2008}), "Insertion of a spin crossover Fe-III complex into an oxalate-based layered material: Coexistence of spin canting and spin crossover in a hybrid magnet" , INORGANIC CHEMISTRY. , OCT 6, {2008}. Vol. {47} ({19}) , pp. {9111-9120}. |
| Abstract: The syntheses, structures, and magnetic properties of the compounds of formula [Fe-III(sal(2)trien)](2)[Mn-2(II)(ox)(3)]center dot 4H(2)O center dot C3H7NO (1) and [In-III(sal(2)trien)](2)[Mn-2(II)(ox)(3)]center dot 3H(2)O center dot CH3OH (2) are reported The structure presents a homometallic 2D honeycomb anionic layer formed by Mn-II ions linked through oxalate ligands and a cationic double layer of [Fe(sal(2)trien)](+) or [In(sal(2)trien)](+) complexes intercalated between the 2D oxalate network. The magnetic properties and Mossbauer spectroscopy of 1 indicate the coexistence of a magnetic ordering of the Mn(II) oxalate network that behaves as a weak ferromagnet and a gradual spin crossover of the intercalated [Fe(sal(2)trien)](+) complexes. |
BibTeX:
@article{ISI:000259603800086,
author = {Clemente-Leon, Miguel and Coronado, Eugeno and Carmen Gimenez-Lopez, M. and Soriano-Portillo, Alejandra and Waerenborgh, Joao C. and Delgado, Fernando S. and Ruiz-Perez, Catalina},
title = {Insertion of a spin crossover Fe-III complex into an oxalate-based layered material: Coexistence of spin canting and spin crossover in a hybrid magnet},
journal = {INORGANIC CHEMISTRY},
year = {2008},
volume = {47},
number = {19},
pages = {9111-9120},
doi = {{10.1021/ic801165b}}
}
|
| Cruz, H. & Luis, D. ({2011}), "Coulomb effects and sub-band tunneling in quantum wells" , JOURNAL OF APPLIED PHYSICS. , APR 1, {2011}. Vol. {109} ({7}) |
| Abstract: We have solved, in space and time, the effective-mass nonlinear Schrodinger equation for two electron gases in a semiconductor structure. Considering a Coulomb interaction between the electron densities of each sub-band, we have obtained two time-varying moments in the heterostructure with two different frequencies. If the carrier densities are large enough, we have obtained important nonlinear effects in the carrier dynamics. In this way, we have shown the possibility of having another kind of terahertz electromagnetic radiation emerging from a double quantum well device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3573485] |
BibTeX:
@article{ISI:000289949000073,
author = {Cruz, H. and Luis, D.},
title = {Coulomb effects and sub-band tunneling in quantum wells},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2011},
volume = {109},
number = {7},
doi = {{10.1063/1.3573485}}
}
|
| Cruz, H. & Luis, D. ({2009}), "Coulomb effects and carrier diffusion in semiconductor quantum wires" , JOURNAL OF APPLIED PHYSICS. , AUG 15, {2009}. Vol. {106} ({4}) |
| Abstract: We have solved in space and time the effective-mass nonlinear Schrodinger equation for an electron-hole gas in a semiconductor quantum wire. If the carrier density is large enough, we have obtained the diffusion of coupled electron and hole densities considering a Coulomb interaction between both electron-hole gases. In this way, we have shown the possibility of having an inverse Mott transition in a quantum wire after an optical excitation of the sample. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3195083] |
BibTeX:
@article{ISI:000270083800053,
author = {Cruz, H. and Luis, D.},
title = {Coulomb effects and carrier diffusion in semiconductor quantum wires},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2009},
volume = {106},
number = {4},
doi = {{10.1063/1.3195083}}
}
|
| Cruz, H. & Luis, D. ({2008}), "Quantum measurement and charge density oscillations in double quantum dots" , INTERNATIONAL JOURNAL OF QUANTUM INFORMATION. , JUL, {2008}. Vol. {6} ({Suppl. 1}) , pp. {639-644}. Note:International Meeting on Noise, Information and Complexity AT Quantum Scale, Erice, ITALY, NOV 02-10, 2007. |
| Abstract: In this work, we have studied the post-measurement dynamics of several electrons in a double quantum dot system using a new method of calculation. We have solved the effective-mass non-linear Schrodinger equation for two electron wave packets in a double quantum well taking into account the different number of projected electrons in each quantum well after an observation. It is found the existence of a critical density that reduces strongly the tunneling dynamics between both quantum wells. In addition, we have shown the possibility of having a new kind of electromagnetic radiation emerging from a semiconductor device after a quantum observation. |
BibTeX:
@article{ISI:000258398400012,
author = {Cruz, H. and Luis, D.},
title = {Quantum measurement and charge density oscillations in double quantum dots},
journal = {INTERNATIONAL JOURNAL OF QUANTUM INFORMATION},
year = {2008},
volume = {6},
number = {Suppl. 1},
pages = {639-644},
note = {International Meeting on Noise, Information and Complexity AT Quantum Scale, Erice, ITALY, NOV 02-10, 2007}
}
|
| Cruz, H. & Luis, D. ({2008}), "Possibility of spin device in a triple quantum well system" , JOURNAL OF APPLIED PHYSICS. , OCT 15, {2008}. Vol. {104} ({8}) |
| Abstract: We have numerically integrated in space and time the effective mass nonlinear Schrodinger equation for an electron wave packet in an InAs triple quantum well system. Considering the local spin-density approximation, we have calculated the tunneling dynamics in the triple quantum well system when an external bias is applied in the center quantum well. In such a device, the injected electronic current that is initially unpolarized could be divided into two spin-up and spin-down polarized currents at the same time and voltage obtaining a double efficiency. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3006128] |
BibTeX:
@article{ISI:000260572100059,
author = {Cruz, H. and Luis, D.},
title = {Possibility of spin device in a triple quantum well system},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2008},
volume = {104},
number = {8},
doi = {{10.1063/1.3006128}}
}
|
| Cruz, H. & Luis, D. ({2008}), "Time-dependent tunneling of spin-polarized electrons in coupled quantum wells" , In 395TH WILHELM AND ELSE HERAEUS SEMINAR - TIME DEPENDENT PHENOMENA IN QUANTUM MECHANICS. Vol. {99} Note:395th We-Heraeus Seminar - Time-Dependent Phenomena in Quantum Mechanics, Blaubeuren, GERMANY, SEP 12-16, 2007. |
| Abstract: We have solved the in-plane momentum-dependent effective-mass nonlinear Schrodinger equation for a spin-polarized electron wave packet in a InAs double quantum well system with an interlayer voltage. Considering a time-dependent Hartree potential, we have calculated the spin-polarized nonlinear electron dynamics between both quantum wells at different in-plane momentum values and applied bias. The spin-splitting caused by the Rashba effect is combined with the level matching between the spin dependent resonant tunneling levels making possible the observed local spin density oscillations which depend on the applied bias value. The filtering efficiency has been studied using time-dependent calculations. |
BibTeX:
@inproceedings{ISI:000284324800004,
author = {Cruz, H. and Luis, D.},
title = {Time-dependent tunneling of spin-polarized electrons in coupled quantum wells},
booktitle = {395TH WILHELM AND ELSE HERAEUS SEMINAR - TIME DEPENDENT PHENOMENA IN QUANTUM MECHANICS},
year = {2008},
volume = {99},
note = {395th We-Heraeus Seminar - Time-Dependent Phenomena in Quantum Mechanics, Blaubeuren, GERMANY, SEP 12-16, 2007},
doi = {{10.1088/1742-6596/99/1/012004}}
}
|
| Cruz, H. & Luis, D. ({2005}), "Coulomb effects and terahertz emission in semiconductor superlattices" , JOURNAL OF APPLIED PHYSICS. , SEP 15, {2005}. Vol. {98} ({6}) |
| Abstract: We have solved the effective-mass nonlinear Schrodinger equation for an electron-hole gas in a semiconductor superlattice in space and time. Considering a Coulomb interaction between both electron-hole gases in a semiconductor superlattice we have obtained a time-varying dipole moment in the heterostructure. In this way, we have shown the possibility of another kind of terahertz electromagnetic radiation that emerges from a semiconductor superlattice after optical excitation of the sample. (c) 2005 American Institute of Physics. |
BibTeX:
@article{ISI:000232226000045,
author = {Cruz, H and Luis, D},
title = {Coulomb effects and terahertz emission in semiconductor superlattices},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2005},
volume = {98},
number = {6},
doi = {{10.1063/1.2035892}}
}
|
| Cruz, H., Luis, D., Delgado, F. & Muga, J. ({2004}), "Local spin-density oscillations in coupled quantum wells" , PHYSICAL REVIEW B. , NOV, {2004}. Vol. {70} ({19}) |
| Abstract: We have solved the in-plane momentum-dependent effective-mass nonlinear Schrodinger equation for a spin-polarized electron wave packet in a bilayer electron system. Considering a time-dependent Hartree potential, we have calculated the spin-polarized nonlinear electron dynamics between both quantum wells at different in-plane momentum values. The local spin polarization, which depends on the tunneling dynamics between both electron layers, oscillates together with the spin-polarized charge density. This demonstrates the possibility of having local spin density oscillations in a coupled quantum well system as a function of the electronic sheet density. |
BibTeX:
@article{ISI:000225477800093,
author = {Cruz, H and Luis, D and Delgado, F and Muga, JG},
title = {Local spin-density oscillations in coupled quantum wells},
journal = {PHYSICAL REVIEW B},
year = {2004},
volume = {70},
number = {19},
doi = {{10.1103/PhysRevB.70.195315}}
}
|
| Da Silva, I., Gonzalez-Platas, J., Giacovazzo, C. & Altomare, A. ({2007}), "About the variable-counting-time techniques in powder diffraction data: their use in EXPO2004" , ZEITSCHRIFT FUR KRISTALLOGRAPHIE. Vol. {222} ({12}) , pp. {669-675}. |
| Abstract: High quality data are essential for crystal structure solution, particularly when Direct Methods instead of Global Optimization Techniques are used. In this work we study the performances of the variable-counting-time techniques in the two crucial steps of the phasing process: decomposition of the full diffraction pattern and direct phasing. The experimental data were collected by a conventional X-ray laboratory diffractometer: they were then submitted to the program EXPO2004 for assessing their usefulness in the phasing process. The results are compared with those obtained by using experimental diffraction data collected via the traditional fixed-counting-time technique under the same experimental conditions. |
BibTeX:
@article{ISI:000252708000001,
author = {Da Silva, Ivan and Gonzalez-Platas, Javier and Giacovazzo, Carmelo and Altomare, Angela},
title = {About the variable-counting-time techniques in powder diffraction data: their use in EXPO2004},
journal = {ZEITSCHRIFT FUR KRISTALLOGRAPHIE},
year = {2007},
volume = {222},
number = {12},
pages = {669-675},
doi = {{10.1524/zkri.2007.222.12.669}}
}
|
| Daniel Rodriguez-Armas, V., Tikhomirov, V.K., Mendez-Ramos, J., Yanes, A.C., Del-Castillo, J., Furniss, D. & Seddon, A.B. ({2007}), "Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices - art. no. 65930O" , In Photonic Materials, Devices, and Applications II. Vol. {6593} , pp. {O5930}. Note:Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007. |
| Abstract: We report on optical properties and prospect applications on rare-earth doped oxyfluoride precursor glass and ensuing nano-glass-ceramics. We find out the spectral optical gain of the nano-glass-ceramics and show that its flatness and breadth are advantageous as compared to contemporary used erbium doped optical amplifiers. We present the possibility of flat gain cross-section erbium doped waveguide amplifiers as short `chip', all-optical devices capable of dense wavelength division multiplexing, including the potential for direct writing of these devices inside bulk glasses for three-dimensional photonic integration. We carried out a comparative study of the up-conversion luminescence in Er3+-doped and Yb3+-Er3+-Tm3+ co-doped samples, which indicates that these materials can be used as green/red tuneable up-conversion phosphors and white light simulation respectively. Observed changes in the spectra of the up-conversion luminescence provide a tool for tuning the colour opening the way for producing 3-dimensional optical recording. |
BibTeX:
@inproceedings{ISI:000250171600019,
author = {Daniel Rodriguez-Armas, Vicente and Tikhomirov, Victor K. and Mendez-Ramos, Jorge and Yanes, Angel C. and Del-Castillo, Javier and Furniss, David and Seddon, Angela B.},
title = {Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices - art. no. 65930O},
booktitle = {Photonic Materials, Devices, and Applications II},
year = {2007},
volume = {6593},
pages = {O5930},
note = {Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007},
doi = {{10.1117/12.722035}}
}
|
| Del Castillo, J., Rodriguez, V., Yanes, A., Mendez-Ramos, J. & Torres, M. ({2005}), "Luminescent properties of transparent nanostructured Eu3+ doped SnO2-SiO2 glass-ceramics prepared by the sol-gel method" , NANOTECHNOLOGY. , MAY, {2005}. Vol. {16} ({5, Sp. Iss. SI}) , pp. {S300-S303}. Note:International Conference on Trends in Nanotechnology, Segovia, SPAIN, SEP 13-17, 2004. |
| Abstract: Nanostructured silica based ceramic samples of composition (100 - x)SiO2-xSnO(2), doped with 0.4 mol% of Eu3+ and with x from I to 10, have been developed after a thermal treatment of precursor sol-gel glasses. A structural analysis has been performed by x-ray diffraction and high resolution transmission electron microscopy. The mean radius of the obtained SnO2 nanocrystals, ranging from 2 to 5 nm, is comparable to the exciton Bohr radius, corresponding to wide bandgap semiconductor quantum dots in an insulator SiO2 glass. A spectroscopy study in terms of emission and excitation spectra has been carried out as a function of SnO2 concentration. Moreover, time-resolved fluorescence measurements have also been performed in order to discern the emission of ions in glassy and nanocrystalline environments. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. |
BibTeX:
@article{ISI:000229558100032,
author = {Del Castillo, J and Rodriguez, VD and Yanes, AC and Mendez-Ramos, J and Torres, ME},
title = {Luminescent properties of transparent nanostructured Eu3+ doped SnO2-SiO2 glass-ceramics prepared by the sol-gel method},
journal = {NANOTECHNOLOGY},
year = {2005},
volume = {16},
number = {5, Sp. Iss. SI},
pages = {S300-S303},
note = {International Conference on Trends in Nanotechnology, Segovia, SPAIN, SEP 13-17, 2004},
doi = {{10.1088/0957-4484/16/5/031}}
}
|
| Delgado, F., Kerbellec, N., Ruiz-Perez, C., Cano, J., Lloret, F. & Julve, M. ({2006}), "Malonate-containing manganese(III) complexes: Synthesis, crystal structure, and magnetic properties of AsPh4[Mn(mal)(2)(H2O)(2)]" , INORGANIC CHEMISTRY. , FEB 6, {2006}. Vol. {45} ({3}) , pp. {1012-1020}. |
| Abstract: The novel manganese(III) complexes PPh4[Mn(mal)(2)(H2O)(2)] (1) and AsPh4[Mn(mal)(2)(H2O)(2)] (2) (PPh4+ = tetraphenylphosphonium cation, AsPh4+ = tetraphenylarsonium cation, and H(2)mal = malonic acid) have been prepared, and the structure of 2 was determined by X-ray diffraction analysis. 2 is a mononuclear complex whose structure is made up of trans-diaquabis(malonato)manganate(III) units and tetraphenylarsonium cations. Two crystallographically independent manganese(III) ions (Mn(l) and Mn(2)) occur in 2 that exhibit elongated octahedral surroundings with four oxygen atoms from two bidentate malonate groups in equatorial positions (Mn(1)-O = 1.923(6) and 1.9328(6) angstrom and Mn(2)-O = 1.894(6) and 1.925(6) angstrom) and two trans-coordinated water molecules in the axial sites (Mn(1)-Ow = 2.245(6) angstrom and Mn(2)-Ow = 2.268(6) angstrom). The [Mn(mal)(2)(H2O)(2)](-) units are linked through hydrogen bonds involving the free malonate-oxygen atoms and the coordinated water molecules to yield a quasi-square-type anionic layer growing in the ab plane. The shortest intralayer metal-metal separations are 7.1557(7) and 7.1526(7) angstrom (through the edges of the square). The anionic sheets are separated from each other by layers of AsPh4+ where sextuple- and double-phenyl embraces occur. The magnetic behavior of 1 and 2 in the temperature range 1.9-290 K reveals the occurrence of weak intralayer ferromagnetic interactions (J = +0.081(1) (1) and +0.072(2) cm(-1) (2)). These values are compared to those of the weak antiferromagnetic coupling [J = -0.19(1) cm(-1)], which is observed in the chain compound K-2[Mn(mal)(2)(MeOH)(2)][Mn(mal)(2)] (3), where the exchange pathway involves the carboxyate-malonate bridge in the anti-syn conformation. The structure of 3 was reported elsewhere. Theoretical calculations on fragment models of 2 and 3 were performed to analyze and substantiate both the nature and magnitude of the magnetic couplings observed. |
BibTeX:
@article{ISI:000235198400014,
author = {Delgado, FS and Kerbellec, N and Ruiz-Perez, C and Cano, J and Lloret, F and Julve, M},
title = {Malonate-containing manganese(III) complexes: Synthesis, crystal structure, and magnetic properties of AsPh4[Mn(mal)(2)(H2O)(2)]},
journal = {INORGANIC CHEMISTRY},
year = {2006},
volume = {45},
number = {3},
pages = {1012-1020},
doi = {{10.1021/ic0508526}}
}
|
| Delgado, F., Muga, J., Cruz, H., Luis, D. & Austing, D. ({2005}), "Effects of Coulomb interaction on electron dynamics in a double-barrier potential: Decay and trapping" , PHYSICAL REVIEW B. , NOV, {2005}. Vol. {72} ({19}) |
| Abstract: The decay of a resonance and electron trapping in the quantum well region of a double barrier potential are studied. We take into account electron-electron interactions at the Hartree level by coupling the time-dependent Poisson and Schrodinger equations. Since, in this mean-field theory, the effective potential for the electron motion depends on the classical distribution of charge, the Schrodinger equation becomes nonlinear. We have used the electron sheet density in the well as an adjustable parameter that controls the coupling and thus the degree of the nonlinearity. Without nonlinear coupling, the well generally holds resonance states and, if deep enough, possibly bound states. The nonlinear interaction gives rise to shorter decay times for the resonances, and the existence of a critical electron sheet density above which permanent trapping does not occur. |
BibTeX:
@article{ISI:000233603700085,
author = {Delgado, F and Muga, JG and Cruz, H and Luis, D and Austing, DG},
title = {Effects of Coulomb interaction on electron dynamics in a double-barrier potential: Decay and trapping},
journal = {PHYSICAL REVIEW B},
year = {2005},
volume = {72},
number = {19},
doi = {{10.1103/PhysRevb.72.195318}}
}
|
| Delgado, F.S., Lahoz, F., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2008}), "Supramolecular networks in copper(II) malonate complexes" , CRYSTAL GROWTH & DESIGN. , SEP, {2008}. Vol. {8} ({9}) , pp. {3219-3232}. |
| Abstract: Six new copper(II)-malonate containing complexes [Cu(dpydiol)(mal)(H2O) center dot 2H(2)O (1) (dpydiol = bis(2-pyridyl)-methanediol), [Cu(dpa)(mal)(H2O)] center dot H2O (2) (dpa = 2,2'-dipyridylamine), [Cu(pyim)(mal)(H2O) center dot H2O (3) (pyim = 2-(2-pyridyl)imidazole), [Cu(dpp)(mal)(H2O)] center dot 3/2H(2)O (4) (dpp = 2,3-bis(2-pyridyl)pyrazine), [Cu(phen)(mal) (H2O)] center dot H2O (5), and [Cu-2(phen)(2)(mal)(H2O)(3)](NO3)(2) center dot 2H(2)O (6) (phen = 1,10-phenanthroline) were prepared and their structures were determined by single-crystal X-ray diffraction analysis. 1-5 are mononuclear complexes, whereas 6 is a dinuclear species. The neutral mono- and dinuclear units and the crystallization water molecules are linked together by hydrogen bonds to afford three-dimensional networks. In addition, pi center dot center dot center dot pi stacking (2, 5 and 6) and hydrophobic (4 and 6) interactions contribute to the stabilization of the structures. The analysis of the magnetic data of 6 in the temperature range 1.9-300 K shows the occurrence of a significant ferromagnetic interaction between the copper(II) ions through the carboxylate-malonate bridge [J = +6.22(1) cm(-1), the isotropic spin Hamiltonian being defined as (H) over cap = -J (S) over cap (A) center dot (S) over cap (B)]. |
BibTeX:
@article{ISI:000258976100019,
author = {Delgado, Fernando S. and Lahoz, Fernando and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Supramolecular networks in copper(II) malonate complexes},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2008},
volume = {8},
number = {9},
pages = {3219-3232},
doi = {{10.1021/cg701108c}}
}
|
| Delgado, F.S., Ruiz-Perez, C., Sanchiz, J., Lloret, F. & Julve, M. ({2006}), "Versatile supramolecular self-assembly. Part I. Network formation and magnetic behaviour of the alkaline salts of the bis(malonate) cuprate(II) anion" , CRYSTENGCOMM. Vol. {8} ({7}) , pp. {507-529}. |
| Abstract: Five malonate-containing copper(II) compounds of formula [A(H2O)(n)](2) [Cu(mal)(2)(H2O)(m)] [A = Li (1), Na (2), K (3), Rb (4) and Cs (5); H(2)mal = malonic acid] have been synthetized and characterized by X-ray diffraction. The structure of these compounds consists of bis(malonate)-cuprate(II) anions and alkaline cations that are held together by means of carboxylate bridges and water molecules leading to 3D networks. A study of the self-assembling of the bis(malonate) cuprate(II) and the alkaline cations is carried out, the size of the alkaline metal ion playing an important role in the control of the resulting malonate-bridged copper(II) structure. A regular alternation of layers of anionic malonate-copper(II) and cationic alkaline metal atoms occurs compounds 2-5. The alkaline metal ions are connected through mu-oxo bridges affording thus, different cationic motifs: dimers (1), single (2 and 3) and double helical chains (4) and layers (5). Depending on the alkaline cation, the bis(malonate) cuprate(II) units can be linked to each other through malonate carboxylate bridges giving rise to anionic networks which exhibit different topologies: monomers (1 and 5), chains (4) and layers (2 and 3). Variable-temperature (1.9-290 K) magnetic susceptibility measurements show the occurrence of ferromagnetic interactions [ranging from +0.77(1) to +0.90(1) cm(-1)] between the copper(II) ions through the caboxylate-malonate bridge in the out-of-plane anti-anti conformation. |
BibTeX:
@article{ISI:000239173600003,
author = {Delgado, Fernando S. and Ruiz-Perez, Catalina and Sanchiz, Joaquin and Lloret, Francesc and Julve, Miguel},
title = {Versatile supramolecular self-assembly. Part I. Network formation and magnetic behaviour of the alkaline salts of the bis(malonate) cuprate(II) anion},
journal = {CRYSTENGCOMM},
year = {2006},
volume = {8},
number = {7},
pages = {507-529},
doi = {{10.1039/b603374a}}
}
|
| Delgado, F.S., Ruiz-Perez, C., Sanchiz, J., Lloret, F. & Julve, M. ({2006}), "Versatile supramolecular self-assembly - Part II. Network formation and magnetic behaviour of copper(II) malonate anions in ammonium derivatives" , CRYSTENGCOMM. Vol. {8} ({7}) , pp. {530-544}. |
| Abstract: Five new metal-organic compounds of formula A(n)[Cu(mal)(2)(H2O)(m)] ( being an amine cation and H(2)mal = malonic acid) have been structurally and magnetically characterized. The crystal structure of these compounds consists of an alternation of malonate-containing copper(II) anionic and amine cationic layers. Depending on the amine cation, the bis(malonate) cuprate(II) units can be connected to other units through carboxylate bridges resulting in anionic networks which exhibit different topologies: monomers (2 and 5), layers (3 and 4) and three-dimensional structures (1). Hydrogen bonding plays an important role in the self-assembling of metal-organic compounds and how the size of the amine cation, in this case, can control the malonate-bridged copper(II) structure and moreover can tune the magnetic properties of these compounds. Variable-temperature (1.9-290 K) magnetic susceptibility measurements indicate the occurrence of weak ferromagnetic interactions [+0.263(5) and +0.755(1) cm(-1)] between the copper(II) ions through the anti-anti caboxylate-malonate bridges. |
BibTeX:
@article{ISI:000239173600004,
author = {Delgado, Fernando S. and Ruiz-Perez, Catalina and Sanchiz, Joaquin and Lloret, Francesc and Julve, Miguel},
title = {Versatile supramolecular self-assembly - Part II. Network formation and magnetic behaviour of copper(II) malonate anions in ammonium derivatives},
journal = {CRYSTENGCOMM},
year = {2006},
volume = {8},
number = {7},
pages = {530-544},
doi = {{10.1039/b604573a}}
}
|
| Delgado, F.S., Sanchiz, J., Lopez, T., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2010}), "Building-block process for the synthesis of new chromium(III) malonate complexes" , CRYSTENGCOMM. Vol. {12} ({10}) , pp. {2711-2721}. |
| Abstract: We describe the crystal structures of two bimetallic compounds with the malonate and an exo-polydentate N-donor ligand [Cu(tren)](4)[Cr-2(mal)(4)(OH)(2)](ClO4)(4)center dot 8H(2)O (3) and [Ni(Htren)(2)][Cr-2(mal)(4)(OH)(2)]center dot 8H(2)O (4) which are prepared from the dinuclear K-4[Cr-2(mal)(4)(OH)(2)]center dot 6H(2)O precursor (2) [tren = tris(2-aminoethyl) amine and H(2)mal malonic acid]. Their crystal packing and supramolecular structures are analyzed in the context of the influence of the dichromium(III) [Cr-2(mal)(4)(OH)(2)](4-) unit, which acts as a building-block. Different supramolecular motifs built up from hydrogen bonds are discussed, and their self-assembly to yield a 3D arrangement is described. The magnetic properties of the compounds 2-4 have been investigated as a function of the temperature. Weak ferro-(J = +2.41 cm(-1)) and antiferromagnetic (J = -0.21 cm(-1)) interactions within the di-mu-hydroxodichromium(III) unit occur in 2 and 4, respectively, their different nature being mainly dictated by small structural changes in the centrosymmetric di-mu-hydroxodichromium(II) core [Cr(1)-O- Cr(1a) = 99.48(7) (2) and 100.55(13)degrees (4) and Cr(1)...Cr(1a) = 3.0137(6) (2) and 3.0061(6) angstrom (4)]. An overall antiferromagnetic behaviour is observed for 3 with a maximum of the magnetic susceptibility at ca. 10.0 K, the intramolecular Cr(III)...Cr(III) (though the double hydroxo bridge) and Cu(II)...Cr(III) (across the carboxylate-malonate in the anti-syn conformation) magnetic couplings being J = -5.53 and 2.78 cm(-1), respectively. These magnetic parameters are discussed in terms of the structure of the compounds and compared with previous magneto-structural data on di-mu-hydroxodichromium(III) complexes. |
BibTeX:
@article{ISI:000282219100015,
author = {Delgado, Fernando S. and Sanchiz, Joaquin and Lopez, Trinidad and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Building-block process for the synthesis of new chromium(III) malonate complexes},
journal = {CRYSTENGCOMM},
year = {2010},
volume = {12},
number = {10},
pages = {2711-2721},
doi = {{10.1039/b920650g}}
}
|
| Deniz, M., Pasan, J., Fabelo, O., Canadillas-Delgado, L., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2010}), "Metal-organic coordination frameworks based on mixed methylmalonate and 4,4 `-bipiridine ligands: synthesis, crystal structure and magnetic properties" , NEW JOURNAL OF CHEMISTRY. Vol. {34} ({11}) , pp. {2515-2527}. |
| Abstract: Five new complexes of formulae [M-2(4,4'-bpy)(Memal)(2)X-2](n) [M = Fe(III) (2), Mn(II) (3), Co(II) (4), Ni(II) (5) and Zn(II) (6), and X = Cl-/OH- (2) and H2O (3-6); 4,4'-bpy = 4,4'-bipyridine and Memal = methylmalonate dianion] have been synthesized by following the previously reported procedure for [Cu-2(4,4'-bpy)(Memal)(2)(H2O)(2)](n) (1). Moreover, two new phases of the Cu(II)/Memal/4,4'-bpy system, namely [Cu(4,4'-bpy)(2)][Cu(4,4'-bpy)(2)(Memal)(NO3)(H2O)](n)center dot nNO(3)center dot 3.5nH(2)O (7) and [Cu(4,4'-bpy)(2)(Memal)(H2O)](n)center dot nH(2)O (8), were obtained by varying the synthetic conditions. They were all structurally characterized by single crystal X-ray diffraction, and the magnetic properties of 2-5, 7 and 8 were investigated in the temperature range 1.9-295 K. 1-6 are isomorphous compounds whose structure consists of square grids of metal ions linked through anti-syn carboxylate bridges that grow in the crystallographic ac plane. These layers are pillared along the b axis by bis-monodentate 4,4'-bpy ligands to afford a [4(4)6(6)]-sqp three-dimensional net. Ferro-(1 and 5) and antiferromagnetic (2-4) interactions between the metal ions are mediated by the carboxylate bridge in the anti-syn conformation, the bis-monodentate 4,4'-bpy ligand being unable to transmit a significant magnetic coupling. The values of the magnetic coupling (J) for 2-5 are -0.269(3), -0.225(2), -0.05 and + 0.272(3) cm(-1) respectively, the isotropic spin Hamiltonian being (H) over cap = J Sigma (i)(S) over cap (i)center dot(S) over cap (i)+1. Complexes 7 and 8 exhibit quite a different structure, as driven by the 4,4'-bpy groups. A square-grid of [Cu(4,4'-bpy)(2)](2n+)(n) occurs in 7, which grows in the ab plane and is pillared through anti-syn carboxylate bridges from [Cu(Memal)(4,4'-bpy)(2)(NO3)(H2O)] units along the c axis to build up a [4(12)6(3)]-pcu net. Analysis of the magnetic data for this compound shows an overall antiferromagnetic behaviour with the coexistence of ferro-and antiferromagnetic interactions. The structure of 8 consists of linear chains of copper(II) running along the c axis, where aquabis(4,4'-bipyridine) copper(II) units are connected by bis(monodentate) methylmalonate ligands. A significant intrachain antiferromagnetic interaction is observed in 8 through the extended Cu-OCCCO-Cu exchange pathway [J = -1.38(1) cm(-1)]. The assembling role of the 4,4'-bpy coligand in 1-8 and in previous malonate-containing complexes is analyzed and discussed. |
BibTeX:
@article{ISI:000283495200021,
author = {Deniz, Mariadel and Pasan, Jorge and Fabelo, Oscar and Canadillas-Delgado, Laura and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Metal-organic coordination frameworks based on mixed methylmalonate and 4,4 `-bipiridine ligands: synthesis, crystal structure and magnetic properties},
journal = {NEW JOURNAL OF CHEMISTRY},
year = {2010},
volume = {34},
number = {11},
pages = {2515-2527},
doi = {{10.1039/c0nj00436g}}
}
|
| Diaz-Herrera, B., Gonzalez-Diaz, B., Guerrero-Lemus, R., Hernandez-Rodriguez, C., Mendez-Ramos, J. & Rodriguez, V.D. ({2009}), "Photoluminescence of porous silicon stain etched and doped with erbium and ytterbium" , PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES. , FEB, {2009}. Vol. {41} ({4}) , pp. {525-528}. |
| Abstract: A novel low cost process has been developed for application in porous silicon-based photodetectors and solar cells, where conventional doping processes are not affordable because of the high processing cost and technical difficulties. Ytterbium and erbium (Yb3+-Er3+) ions were introduced into luminescent porous silicon stain etched by thermal diffusion. Doping profiles were evaluated by energy-dispersive spectroscopy analysis. The visible and near-infrared photoluminescence of Yb3+-Er3+ co-doped stain-etched porous silicon layers is observed and evaluated under 980 nm pumping. Up-conversion processes that could improve the efficiency of silicon-based solar cells are detected. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000264471700002,
author = {Diaz-Herrera, B. and Gonzalez-Diaz, B. and Guerrero-Lemus, R. and Hernandez-Rodriguez, C. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Photoluminescence of porous silicon stain etched and doped with erbium and ytterbium},
journal = {PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES},
year = {2009},
volume = {41},
number = {4},
pages = {525-528},
doi = {{10.1016/j.physe.2008.09.015}}
}
|
| Diaz-Marrero, A.R., Brito, I., de la Rosa, J.M., D'Croz, L., Fabelo, O., Ruiz-Perez, C., Darias, J. & Cueto, M. ({2009}), "Novel Lactone Chamigrene-Derived Metabolites from Laurencia majuscula" , EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. , MAR, {2009}. ({9}) , pp. {1407-1411}. |
| Abstract: Gomerolactones A-D along with the known majusculone, obtusol, and elatol were isolated from Laurencia majuscula, and their structures were determined spectroscopically. With the aid of Pirkle's reagent at low temperature, NMR spectroscopy was used to determine the absolute configuration at the ring closure carbon atom of a alpha-alkyhdene-gamma-lactone and an alpha-alkylidene-delta-lactone unit embedded in the chamigrene network of compounds 1 and 2, respectively. The absolute stereochemistry of compounds 3 and 4 was determined by Xray analysis. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) |
BibTeX:
@article{ISI:000264683800018,
author = {Diaz-Marrero, Ana R. and Brito, Inmaculada and de la Rosa, Jose M. and D'Croz, Luis and Fabelo, Oscar and Ruiz-Perez, Catalina and Darias, Jose and Cueto, Mercedes},
title = {Novel Lactone Chamigrene-Derived Metabolites from Laurencia majuscula},
journal = {EUROPEAN JOURNAL OF ORGANIC CHEMISTRY},
year = {2009},
number = {9},
pages = {1407-1411},
doi = {{10.1002/ejoc.200801006}}
}
|
| Dominguez, S., Torres, J., Gonzalez-Platas, J., Hummert, M., Schumann, H. & Kremer, C. ({2009}), "Thermodynamic stability and crystal structure of lanthanide complexes with di-2-pyridyl ketone" , JOURNAL OF COORDINATION CHEMISTRY. Vol. {62} ({1}) , pp. {108-119}. |
| Abstract: The di-2-pyridylketone ligand (dpk) exhibits several coordination modes and is a good candidate for preparation of a variety of metal complexes. In this work we present a potentiometric study (in water and in ethanol : water mixtures) of Ln-dpk and Cu(II)-dpk complexes. The thermodynamic stability of the species with La, Sm and Yb is compared to that of Cu(II). In addition, [Ln(NCS)3(py)2C(OEt)(OH)3] (Ln = Pr, Sm, Gd) and [Cu(SCN)2(py)2C(OEt)(OH)]2 2EtOH have been prepared and characterized by X-ray diffraction. |
BibTeX:
@article{ISI:000260926100012,
author = {Dominguez, S. and Torres, J. and Gonzalez-Platas, J. and Hummert, M. and Schumann, H. and Kremer, C.},
title = {Thermodynamic stability and crystal structure of lanthanide complexes with di-2-pyridyl ketone},
journal = {JOURNAL OF COORDINATION CHEMISTRY},
year = {2009},
volume = {62},
number = {1},
pages = {108-119},
doi = {{10.1080/00958970802474797}}
}
|
| Dominguez, S., Torres, J., Peluffo, F., Mederos, A., Gonzalez-Platas, J., Castiglioni, J. & Kremer, C. ({2007}), "Mixed 3d/4f polyniaclear complexes with 2,2 `-oxydiacetate as bridging ligand: Synthesis, structure and chemical speciation of La-M compounds (M = bivalent cation)" , JOURNAL OF MOLECULAR STRUCTURE. , MAR 17, {2007}. Vol. {829} ({1-3}) , pp. {57-64}. |
| Abstract: Heterometallic compounds containing La(III), bivalent cations M (M = Co, Ni, Ca), and 2,2'-oxydiacetate (oda) as connecting ligand have been prepared and characterized. The complexes can be formulated as [La2M3(oda)(6)(H2O)(6)](.) 12H(2)O. The structure of [La2CO3(oda)(6)(H2O)(6)] shows the presence of the La(III) coordinated by six carboxy and three ether oxygen atoms, and the Co(H) cation bonded to four carboxy oxygens and two molecules of water. An open 3D framework is observed, containing large hexagonal channels. The chemical systems were also investigated in solution (25.0 degrees C, I= 0. 5 M Me4NCl) by potentiometry. The same kind of polynuclear species have been found in aqueous solution. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000244830100008,
author = {Dominguez, Sixto and Torres, Julia and Peluffo, Florencia and Mederos, Alfredo and Gonzalez-Platas, Javier and Castiglioni, Jorge and Kremer, Carlos},
title = {Mixed 3d/4f polyniaclear complexes with 2,2 `-oxydiacetate as bridging ligand: Synthesis, structure and chemical speciation of La-M compounds (M = bivalent cation)},
journal = {JOURNAL OF MOLECULAR STRUCTURE},
year = {2007},
volume = {829},
number = {1-3},
pages = {57-64},
doi = {{10.1016/j.molstruc.2006.06.008}}
}
|
| Driesen, K., Tikhomirov, V., Gorller-Walrand, C., Rodriguez, V. & Seddon, A. ({2006}), "Transparent Ho3+-doped nano-glass-ceramics for efficient infrared emission" , APPLIED PHYSICS LETTERS. , FEB 13, {2006}. Vol. {88} ({7}) |
| Abstract: We developed transparent 3.5 mol % Ho3+-doped oxyfluoride nano-glass-ceramics, where the Ho3+-dopants dissolve in the 6 nm diameter beta-PbF2 nanocrystals. The cubic site of Ho3+ and a low vibration frequency of its PbF2 environment result in an intense and 50 nm broad emission band I-5(6)-> I-5(8) of Ho3+ at 1.2 mu m with a temperature independent lifetime of 1.6 ms. Another 40 nm broad emission band F-5(5)-> I-5(6) at 1.47 mu m with a lifetime of 24 mu s was also excited, the lifetime of this band increased to 60 mu s at 77 K. These two bands have potential application for optical amplification in telecommunications. |
BibTeX:
@article{ISI:000235393700092,
author = {Driesen, K and Tikhomirov, VK and Gorller-Walrand, C and Rodriguez, VD and Seddon, AB},
title = {Transparent Ho3+-doped nano-glass-ceramics for efficient infrared emission},
journal = {APPLIED PHYSICS LETTERS},
year = {2006},
volume = {88},
number = {7},
doi = {{10.1063/1.2174829}}
}
|
| Dul, M.-C., Ferrando-Soria, J., Pardo, E., Lescouezec, R., Journaux, Y., Ruiz-Garcia, R., Cano, J., Julve, M., Lloret, F., Fabelo, O., Pasan, J. & Ruiz-Perez, C. ({2010}), "Tuning the Spin Ground State in Heterononanuclear Nickel(II)-Copper(II) Cylinders with a Triangular Metallacyclophane Core" , INORGANIC CHEMISTRY. , DEC 20, {2010}. Vol. {49} ({24}) , pp. {11264-11266}. |
| Abstract: Two new heterometallic (NinCu(9-n)II)-Cu-II complexes [n = 1 (2) and 2 (3)] have been synthesized following a multicomponent self-assembly process from a n:(3 - n):2:6 stoichiometric mixture of Ni2+, Cu2+, L6-, and [CuL'](2+), where L and L' are the bridging and blocking ligands 1,3,5-benzenetris(oxamate) and N,N,N',N' N `'-pentamethyldiethylenetriamine, respectively. Complexes 2 and 3 possess a unique cyclindrical architecture formed by three oxamato-bridged trinuclear linear units connected through two 1,3,5-substituted benzenetris(amidate) bridges, giving a triangular metallacyclophane core. They behave as a ferromagnetically coupled trimer of two (2)/one (3) S = 1/2 Cu-3(II) plus one (2)/two (3) S = 0 (NiCu2II)-Cu-II linear units with overall S = 1 (NiCu8II)-Cu-II (2) and S = 1/2 (Ni2Cu7II)-Cu-II (3) ground states. |
BibTeX:
@article{ISI:000285266800002,
author = {Dul, Marie-Claire and Ferrando-Soria, Jesus and Pardo, Emilio and Lescouezec, Rodrigue and Journaux, Yves and Ruiz-Garcia, Rafael and Cano, Joan and Julve, Miguel and Lloret, Francesc and Fabelo, Oscar and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Tuning the Spin Ground State in Heterononanuclear Nickel(II)-Copper(II) Cylinders with a Triangular Metallacyclophane Core},
journal = {INORGANIC CHEMISTRY},
year = {2010},
volume = {49},
number = {24},
pages = {11264-11266},
doi = {{10.1021/ic102037m}}
}
|
| Dul, M.-C., Pardo, E., Lescouezec, R., Chamoreau, L.-M., Villain, F., Journaux, Y., Ruiz-Garcia, R., Cano, J., Julve, M., Lloret, F., Pasan, J. & Ruiz-Perez, C. ({2009}), "Redox Switch-Off of the Ferromagnetic Coupling in a Mixed-Spin Tricobalt(II) Triple Mesocate" , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. , OCT 21, {2009}. Vol. {131} ({41}) , pp. {14614+}. |
| Abstract: A prelude to redox-based, ferromagnetic ``metal-organic switches'' is exemplified by a new trinuclear oxalamide cobalt triple mesocate that presents two redox states (ON and OFF) with dramatically different magnetic properties; the two terminal high-spin d(7) Co-II ions (S = 3/2) that are ferromagnetically coupled in the homovalent tricobalt(II) reduced state (2) become uncoupled in the heterovalent tricobalt(II,III,II) oxidized state (2(ox)) upon one-electron oxidation of the central low-spin d(7) Co-II ion (S = 1/2) to a low-spin d(6) Co-III ion (S = 0). |
BibTeX:
@article{ISI:000271271800008,
author = {Dul, Marie-Claire and Pardo, Emilio and Lescouezec, Rodrigue and Chamoreau, Lise-Marie and Villain, Francoise and Journaux, Yves and Ruiz-Garcia, Rafael and Cano, Joan and Julve, Miguel and Lloret, Francesc and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Redox Switch-Off of the Ferromagnetic Coupling in a Mixed-Spin Tricobalt(II) Triple Mesocate},
journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
year = {2009},
volume = {131},
number = {41},
pages = {14614+},
doi = {{10.1021/ja9052202}}
}
|
| Dul, M.-C., Pardo, E., Lescouezec, R., Journaux, Y., Ferrando-Soria, J., Ruiz-Garcia, R., Cano, J., Julve, M., Lloret, F., Cangussu, D., Pereira, C.L.M., Stumpf, H.O., Pasan, J. & Ruiz-Perez, C. ({2010}), "Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials" , COORDINATION CHEMISTRY REVIEWS. , OCT, {2010}. Vol. {254} ({19-20, Sp. Iss. SI}) , pp. {2281-2296}. |
| Abstract: The impressive potential of the metallosupramolecular approach in designing new functional magnetic materials constitutes a great scientific challenge for the chemical research community that requires an interdisciplinary collaboration New fundamental concepts and future applications in nanoscience and nanotechnology will emerge from the study of magnetism as a supramolecular function in metallosupramolecular chemistry. Our recent work on the rich supramolecular coordination chemistry of a novel family of aromatic polyoxalamide (APOXA) ligands with first-row transition metal ions has allowed us to move one step further in the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity Thus, we have taken advantage of the new developments of metallosupramolecular chemistry and, in particular, the molecular-programmed self-assembly methods that exploit the coordination preferences of paramagnetic metal ions and suitable designed polytopic ligands. The resulting self-assembled di- and trinuclear metallacyclic complexes with APOXA ligands, either metallacyclophanes or metallacryptands, are indeed ideal model systems for the study of the electron exchange mechanism between paramagnetic metal centers through extended pi-conjugated aromatic bridges So, the influence of different factors such as the topology and conformation of the bridging ligand or the electronic configuration and magnetic anisotropy of the metal ion have been investigated in a systematic way These oligonuclear metallacyclic complexes can be important in the development of a new class of molecular magnetic devices, such as molecular magnetic wires (MMWs) and switches (MMSs), which are major goals in the field of molecular electronics and spintronics On the other hand, because of their metal binding capacity through the outer carbonyl-oxygen atoms of the oxamato groups, they can further be used as ligands, referred to as metal-organic ligands (MOLs), toward either coordinatively unsaturated metal complexes or fully solvated metal ions. This well-known ``complex-as-ligand'' approach affords a wide variety of high-nuclearity metal-organic clusters (MOCs) and high-dimensionality metal-organic polymers (MOPS) The judicious choice of the oligonuclear MOL. ranging from mono- to di- and trinuclear species, has allowed us to control the overall structure and magnetic properties of the final oxamato-bridged multidimensional (nD, n = 0-3) MOCs and MOPs. The intercrossing between short- (nanoscopic) and long-range (macroscopic) magnetic behavior has been investigated in this unique family of oxamato-bridged metallosupramolecular magnetic materials expanding the examples of low-dimensional, single-molecule (SMMs) and single-chain (SCMs) magnets and high-dimensional, open-framework magnets (OFMs), which are brand-new targets in the field of molecular magnetism and materials science. (C) 2010 Elsevier B V. All rights reserved |
BibTeX:
@article{ISI:000281617800004,
author = {Dul, Marie-Claire and Pardo, Emilio and Lescouezec, Rodrigue and Journaux, Yves and Ferrando-Soria, Jesus and Ruiz-Garcia, Rafael and Cano, Joan and Julve, Miguel and Lloret, Francesc and Cangussu, Danielle and Pereira, Cynthia L. M. and Stumpf, Humberto O. and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Supramolecular coordination chemistry of aromatic polyoxalamide ligands: A metallosupramolecular approach toward functional magnetic materials},
journal = {COORDINATION CHEMISTRY REVIEWS},
year = {2010},
volume = {254},
number = {19-20, Sp. Iss. SI},
pages = {2281-2296},
doi = {{10.1016/j.ccr.2010.03.003}}
}
|
| El-Himri, A., Perez-Coll, D., Nunez, P., Martin, I., Lavin, V. & Rodriguez, V. ({2004}), "Preparation and optical spectroscopy of Eu3+-doped GaN luminescent semiconductor from freeze-dried precursors" , JOURNAL OF SOLID STATE CHEMISTRY. , NOV, {2004}. Vol. {177} ({11}) , pp. {4213-4220}. |
| Abstract: Pure and 0.5% and 5mol% Eu3+ doped GaN nanoparticles have been prepared by ammonolysis of the corresponding freeze-dried precursors. A single hexagonal phase with the wurtzite structure was obtained as determined by X-ray Powder Diffraction. The crystallite size determined by XRD was lower than 10 nm. From optical spectroscopy characterization, it is found that the Eu2O3 formation is avoided by using nitrates as starting reagent. Fluorescence line narrowing spectra show excitation wavelength dependence, which is indicative that the Eu3+ ions are well dispersed in the prepared samples. The environment distribution occupied by the Eu3+ ions has been analyzed by crystal-field calculation and the results are compared with those for other materials. (C) 2004 Elsevier Inc. All rights reserved. |
BibTeX:
@article{ISI:000225508800051,
author = {El-Himri, A and Perez-Coll, D and Nunez, P and Martin, IR and Lavin, V and Rodriguez, VD},
title = {Preparation and optical spectroscopy of Eu3+-doped GaN luminescent semiconductor from freeze-dried precursors},
journal = {JOURNAL OF SOLID STATE CHEMISTRY},
year = {2004},
volume = {177},
number = {11},
pages = {4213-4220},
doi = {{10.1016/j.jssc.2004.08.004}}
}
|
| Ene, C.D., Tuna, F., Fabelo, O., Ruiz-Perez, C., Madalan, A.M., Roesky, H.W. & Andruh, M. ({2008}), "One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis, crystal structures and magnetic properties" , POLYHEDRON. , FEB 6, {2008}. Vol. {27} ({2}) , pp. {574-582}. |
| Abstract: Four new coordination polymers were obtained by employing polycarboxylato spacers and cationic copper(II) complexes as nodes: 2(infinity)[Cu-3(trim)(2)(NH3)(6)(H2O)(3)] (1); 1(infinity)[Cu(tmen)(dhtp)] (2), 1(infinity)[Cu(tmen)(hitp)(H2O)] (3), 1[Cu(tmen)(nitp)] (4). (H(3)trim = trimesic acid, H(2)dhtp = 2,5-dihydroxy-terephthalic acid; H(2)hitp = 5-hydroxy-isophthalic acid, H(2)nitp = 5-nitro-isophthalic acid; tmen = N,N,N',N'-tetramethyl-ethylenediamine). The crystal structures of the four compounds have been solved. Compound 1 consists of 2D coordination polymers with heart-shaped meshes, while compounds 2-4 contain infinite zigzag chains. The role of the hydrogen bond interactions in sustaining the supramolecular solid-state architectures in compounds 1 and 3 is discussed. The cryomagnetic investigation of compounds 1, 2, and 4 reveals antiferromagnetic interactions between the copper ions. (c) 2007 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000253518700013,
author = {Ene, Cristian D. and Tuna, Floriana and Fabelo, Oscar and Ruiz-Perez, Catalina and Madalan, Augustin M. and Roesky, Herbert W. and Andruh, Marius},
title = {One-dimensional and two-dimensional coordination polymers constructed from copper(II) nodes and polycarboxylato spacers: Synthesis, crystal structures and magnetic properties},
journal = {POLYHEDRON},
year = {2008},
volume = {27},
number = {2},
pages = {574-582},
doi = {{10.1016/j.poly.2007.10.011}}
}
|
| Errandonea, D., Ferrer-Roca, C., Martinez-Garcia, D., Segura, A., Gomis, O., Munoz, A., Rodriguez-Hernandez, P., Lopez-Solano, J., Alconchel, S. & Sapina, F. ({2010}), "High-pressure x-ray diffraction and ab initio study of Ni2Mo3N, Pd2Mo3N, Pt2Mo3N, Co3Mo3N, and Fe3Mo3N: Two families of ultra-incompressible bimetallic interstitial nitrides" , PHYSICAL REVIEW B. , NOV 8, {2010}. Vol. {82} ({17}) |
| Abstract: We have studied by means of high-pressure x-ray diffraction the structural stability of Ni2Mo3N, Co3Mo3N, and Fe3Mo3N. We also report ab initio computing modeling of the high-pressure properties of these compounds, Pd2Mo3N and Pt2Mo3N. We have found that the nitrides remain stable in the ambient-pressure cubic structure at least up to 50 GPa and determined their equation of state. All of them have a bulk modulus larger than 300 GPa. Single-crystal elastic constants have been calculated in order to quantify the stiffness of the investigated nitrides. We found that they should have a Vickers hardness similar to that of cubic spinel nitrides such as gamma-Si3N4. |
BibTeX:
@article{ISI:000283923200001,
author = {Errandonea, D. and Ferrer-Roca, Ch. and Martinez-Garcia, D. and Segura, A. and Gomis, O. and Munoz, A. and Rodriguez-Hernandez, P. and Lopez-Solano, J. and Alconchel, S. and Sapina, F.},
title = {High-pressure x-ray diffraction and ab initio study of Ni2Mo3N, Pd2Mo3N, Pt2Mo3N, Co3Mo3N, and Fe3Mo3N: Two families of ultra-incompressible bimetallic interstitial nitrides},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {82},
number = {17},
doi = {{10.1103/PhysRevB.82.174105}}
}
|
| Errandonea, D., Kumar, R., Lopez-Solano, J., Rodriguez-Hernandez, P., Munoz, A., Rabie, M.G. & Saez Puche, R. ({2011}), "Experimental and theoretical study of structural properties and phase transitions in YAsO4 and YCrO4" , PHYSICAL REVIEW B. , APR 8, {2011}. Vol. {83} ({13}) |
| Abstract: We have performed experimental and theoretical studies of the structural stability of YAsO4 and YCrO4 at high pressures. X-ray-diffraction experiments together with ab initio total-energy and lattice-dynamics calculations have allowed us to completely characterize a pressure-induced structural phase transition from the zircon to the scheelite structure in both compounds. Furthermore, total-energy calculations have been performed to check the relative stabilities of different candidate structures at different pressures and allow us to propose for YAsO4 the zircon -> scheelite -> SrUO4-type sequence of structures. In this sequence, sixfold arsenic coordination is attained for the SrUO4-type structure above 32 GPa. The whole sequence of transitions is discussed in comparison with YVO4, YPO4, YNbO4, YMoO4, and YTaO4. Also a comparative discussion of lattice-dynamics properties is presented. The band gap for YAsO4 and YCrO4 and the band structure for YAsO4 are also reported. Finally, the room-temperature equation of state of different compounds is also obtained. |
BibTeX:
@article{ISI:000289349300002,
author = {Errandonea, D. and Kumar, R. and Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A. and Rabie, M. G. and Saez Puche, R.},
title = {Experimental and theoretical study of structural properties and phase transitions in YAsO4 and YCrO4},
journal = {PHYSICAL REVIEW B},
year = {2011},
volume = {83},
number = {13},
doi = {{10.1103/PhysRevB.83.134109}}
}
|
| Errandonea, D., Manjon, F.J., Garro, N., Rodriguez-Hernandez, P., Radescu, S., Mujica, A., Munoz, A. & Tu, C.Y. ({2008}), "Combined Raman scattering and ab initio investigation of pressure-induced structural phase transitions in the scintillator ZnWO4" , PHYSICAL REVIEW B. , AUG, {2008}. Vol. {78} ({5}) |
| Abstract: The room-temperature Raman scattering was measured in ZnWO4 up to 45 GPa. We report the pressure dependence of all the Raman-active phonons of the low-pressure wolframite phase. As pressure increases additional Raman peaks appear at 30.6 GPa due to the onset of a reversible structural phase transition to a distorted monoclinic beta-fergusonite-type phase. The low-pressure and high-pressure phases coexist from 30.6 to 36.5 GPa. In addition to the Raman measurements we also report ab initio total-energy and lattice-dynamics calculations for the two phases. These calculations helped us to determine the crystalline structure of the high-pressure phase and to assign the observed Raman modes in both the wolframite and beta-fergusonite phases. Based upon the ab initio calculations we propose the occurrence of a second phase transition at 57.6 GPa from the beta-fergusonite phase to an orthorhombic Cmca phase. The pressure evolution of the lattice parameters and the atomic positions of wolframite ZnWO4 are also theoretically calculated, and an equation of state reported. |
BibTeX:
@article{ISI:000259368200042,
author = {Errandonea, D. and Manjon, F. J. and Garro, N. and Rodriguez-Hernandez, P. and Radescu, S. and Mujica, A. and Munoz, A. and Tu, C. Y.},
title = {Combined Raman scattering and ab initio investigation of pressure-induced structural phase transitions in the scintillator ZnWO4},
journal = {PHYSICAL REVIEW B},
year = {2008},
volume = {78},
number = {5},
doi = {{10.1103/PhysRevB.78.054116}}
}
|
| Errandonea, D., Pellicer-Porres, J., Manjon, F., Segura, A., Ferrer-Roca, C., Kumar, R., Tschauner, O., Lopez-Solano, J., Rodriguez-Hernandez, P., Radescu, S., Mujica, A., Munoz, A. & Aquilanti, G. ({2006}), "Determination of the high-pressure crystal structure of BaWO4 and PbWO4" , PHYSICAL REVIEW B. , JUN, {2006}. Vol. {73} ({22}) |
| Abstract: We report the results of both angle-dispersive x-ray diffraction and x-ray absorption near-edge structure studies in BaWO4 and PbWO4 at pressures of up to 56 GPa and 24 GPa, respectively. BaWO4 is found to undergo a pressure-driven phase transition at 7.1 GPa from the tetragonal scheelite structure (which is stable under normal conditions) to the monoclinic fergusonite structure whereas the same transition takes place in PbWO4 at 9 GPa. We observe a second transition to another monoclinic structure which we identify as that of the isostructural phases BaWO4-II and PbWO4-III (space group P2(1)/n). We have also performed ab initio total-energy calculations which support the stability of this structure at high pressures in both compounds. The theoretical calculations further find that upon increase of pressure the scheelite phases become locally unstable and transform displacively into the fergusonite structure. The fergusonite structure is, however, metastable and can only occur if the transition to the P2(1)/n phases were kinetically inhibited. Our experiments in BaWO4 indicate that it becomes amorphous beyond 47 GPa. |
BibTeX:
@article{ISI:000238696300018,
author = {Errandonea, D and Pellicer-Porres, J and Manjon, FJ and Segura, A and Ferrer-Roca, C and Kumar, RS and Tschauner, O and Lopez-Solano, J and Rodriguez-Hernandez, P and Radescu, S and Mujica, A and Munoz, A and Aquilanti, G},
title = {Determination of the high-pressure crystal structure of BaWO4 and PbWO4},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {73},
number = {22},
doi = {{10.1103/PhysRevB.73.224103}}
}
|
| Errandonea, D., Pellicer-Porres, J., Manjon, F., Segura, A., Ferrer-Roca, C., Kumar, R., Tschauner, O., Rodriguez-Hernandez, P., Lopez-Solano, J., Radescu, S., Mujica, A., Munoz, A. & Aquilanti, G. ({2005}), "High-pressure structural study of the scheelite tungstates CaWO4 and SrWO4" , PHYSICAL REVIEW B. , NOV, {2005}. Vol. {72} ({17}) |
| Abstract: Angle-dispersive x-ray-diffraction and x-ray-absorption near-edge structure measurements have been performed on CaWO4 and SrWO4 up to pressures of approximately 20 GPa. Both materials display similar behavior in the range of pressures investigated in our experiments. As in the previously reported case of CaWO4, under hydrostatic conditions SrWO4 undergoes a pressure-induced scheelite-to-fergusonite transition around 10 GPa. Our experimental results are compared to those found in the literature and are further supported by ab initio total-energy calculations, from which we also predict the instability at larger pressures of the fergusonite phases against an orthorhombic structure with space group Cmca. Finally, a linear relationship between the charge density in the AO(8) polyhedra of ABO(4) scheelite-related structures and their bulk modulus is discussed and used to predict the bulk modulus of other materials, like hafnon. |
BibTeX:
@article{ISI:000233603500039,
author = {Errandonea, D and Pellicer-Porres, J and Manjon, FJ and Segura, A and Ferrer-Roca, C and Kumar, RS and Tschauner, O and Rodriguez-Hernandez, P and Lopez-Solano, J and Radescu, S and Mujica, A and Munoz, A and Aquilanti, G},
title = {High-pressure structural study of the scheelite tungstates CaWO4 and SrWO4},
journal = {PHYSICAL REVIEW B},
year = {2005},
volume = {72},
number = {17},
doi = {{10.1103/PhysRevB.72.174106}}
}
|
| Errandonea, D., Santamaria-Perez, D., Vegas, A., Nuss, J., Jansen, M., Rodriguez-Hernandez, P. & Munoz, A. ({2008}), "Structural stability of Fe5Si3 and Ni2Si studied by high-pressure x-ray diffraction and ab initio total-energy calculations" , PHYSICAL REVIEW B. , MAR, {2008}. Vol. {77} ({9}) |
| Abstract: We performed high- pressure angle dispersive x- ray diffraction measurements on Fe5Si3 and Ni2Si up to 75 GPa. Both materials were synthesized in bulk quantities via a solid- state reaction. In the pressure range covered by the experiments, no evidence of the occurrence of phase transitions was observed. On top of that, Fe5Si3 was found to compress isotropically, whereas an anisotropic compression was observed in Ni2Si. The linear incompressibility of Ni2Si along the c axis is similar in magnitude to the linear incompressibility of diamond. This fact is related to the higher valence- electron charge density of N(i)2Si along the c axis. The observed anisotropic compression of Ni2Si is also related to the layered structure of Ni2Si, where hexagonal layers of Ni2+ cations alternate with graphite- like layers formed by ( NiSi)(2-) entities. The experimental results are supported by ab initio total- energy calculations carried out using density functional theory and the pseudopotential method. For Fe5Si3, the calculations also predicted a phase transition at 283 GPa from the hexagonal P6(3) / mcm phase to the cubic structure adopted by Fe and Si in the garnet Fe5Si3O12. The room- temperature equations of state for Fe5Si3 and Ni2Si are also reported and a possible correlation between the bulk modulus of iron silicides and the coordination number of their minority element is discussed. Finally, we report additional descriptions of these structures, in particular, of the predicted high- pressure phase of Fe5Si3 (the cation subarray in the garnet Fe5Si3O12 ), which can be derived from spinel Fe2SiO4 (Fe6Si3O12). |
BibTeX:
@article{ISI:000254542500045,
author = {Errandonea, D. and Santamaria-Perez, D. and Vegas, A. and Nuss, J. and Jansen, M. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Structural stability of Fe5Si3 and Ni2Si studied by high-pressure x-ray diffraction and ab initio total-energy calculations},
journal = {PHYSICAL REVIEW B},
year = {2008},
volume = {77},
number = {9},
doi = {{10.1103/PhysRevB.77.094113}}
}
|
| Errandonea, D., Tu, C., Ha, G., Martin, I.R., Rodriguez-Mendoza, U.R., Lahoz, F., Torres, M.E. & Lavin, V. ({2008}), "Effect of pressure on the luminescence properties of Nd3+ doped SrWO4 laser crystal" , JOURNAL OF ALLOYS AND COMPOUNDS. , FEB 28, {2008}. Vol. {451} ({1-2}) , pp. {212-214}. Note:6th International Conference on f-Elements (ICFE-6), Wroclaw, POLAND, SEP 04-09, 2006. |
| Abstract: The luminescence spectra of the F-4(3/2) -> I-4(9/2) transition of Nd3+ ions in a SrWO4 crystal have been analyzed as a function of pressure at room temperature. Experiments have been performed in a diamond-anvil cell up to 13 GPa. At around 10 GPa some changes in the emission spectra have been observed which are attributed to a structural phase transition of the SrWO4 matrix. These results are in good agreement with a previous paper, in which in a pure SrWO4 matrix a scheelite to fergusonite phase transition is found around 10.5 GPa. Moreover, with increasing pressure, the decay curves from the F-4(3/2) are nonexponential and faster indicating that the energy transfer processes between Nd3+ ions are important. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000253600400047,
author = {Errandonea, D. and Tu, Chaoyang and Ha, Guohua and Martin, I. R. and Rodriguez-Mendoza, U. R. and Lahoz, F. and Torres, M. E. and Lavin, V.},
title = {Effect of pressure on the luminescence properties of Nd3+ doped SrWO4 laser crystal},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2008},
volume = {451},
number = {1-2},
pages = {212-214},
note = {6th International Conference on f-Elements (ICFE-6), Wroclaw, POLAND, SEP 04-09, 2006},
doi = {{10.1016/j.jallcom.2007.04.180}}
}
|
| Fabelo, O., Canadillas-Delgado, L., Delgado, F., Lorenzo-Luis, P., Laz, M., Julve, M. & Ruiz-Perez, C. ({2005}), "Hydrogen bond-directed frameworks based on 1,2,4,5-benzene-tetracarboxylate" , CRYSTAL GROWTH & DESIGN. , MAY-JUN, {2005}. Vol. {5} ({3}) , pp. {1163-1167}. |
| Abstract: The deprotonated forms of 1,2,4,5-benzenetetracarboxylic acid H(4)bta can act not only as hydrogenbond acceptors but also as hydrogen-bond donors, depending on the deprotonated carboxyl groups given different supramolecular adducts. A search of the Cambridge Structural Database (CSD) of cocrystal structures of H(4)bta with L = 4,4'-bpy or bpe has found three different adducts: [HL](2)[H(2)bta], [H2L][H(2)bta], and [H2L][H(3)bta], where cocrystal structures of [HL](2)[H(2)bta] with L = 4,4'-bpy or bpe form similar supramolecular arrangements. To investigate this similarity, two new organic salts of the formula [H-2-4,4'-bpy][H(2)bta] - 2H(2)O (1) and [H(2)bpe] [H(3)bta](2) - 4H(2)O (2) have been characterized. In the 1:1 adduct 1, the molecular components are linked by hydrogen bonds of the N-H---O type creating chains. These chains are further linked by C-H---O type interactions (C-H from the cation and O from the anion) creating a two-dimensional motif. Two types of centrosymmetric rings are evident in the sheets. The stacked sheets are held together via π---π interactions to create a three-dimensional network. Two types of channels, one hydrophilic and the other hydrophobic, run parallel to the a-axis. Water molecules are hydrogen bonded in the hydrophilic channels. The supramolecular structure in the 2:1 adduct 2 is due to hydrogen bonds of the O-H---O and N-H---O types that afford a railroad network along the a-axis. Two water molecules are held in the railroad cavities by hydrogen bonds with carboxylate oxygen atoms. Adjacent railroad chains are linked through hydrogen bonds involving water molecules, building a two-dimensional structure. |
BibTeX:
@article{ISI:000228940600043,
author = {Fabelo, O and Canadillas-Delgado, L and Delgado, FS and Lorenzo-Luis, P and Laz, MM and Julve, M and Ruiz-Perez, C},
title = {Hydrogen bond-directed frameworks based on 1,2,4,5-benzene-tetracarboxylate},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2005},
volume = {5},
number = {3},
pages = {1163-1167},
doi = {{10.1021/cg049625p}}
}
|
| Fabelo, O., Canadillas-Delgado, L., Pasan, J., Ruiz-Perez, C. & Julve, M. ({2006}), "Influence of the presence of divalent first-row transition metal ions on the structure of sodium(I) salts of 1,2,3,4-benzenetetracarboxylic acid (H(4)bta)" , CRYSTENGCOMM. Vol. {8} ({4}) , pp. {338-345}. |
| Abstract: Three different sodium(I)-containing salts of 1,2,4,5-benzenetetracarboxylic (H(4)bta) of formula [Na-4(bta)(H2O)(12)] (1), [Na2M(H(2)bta) 2(H2O)(8)] center dot 2H(2)O] [M = Mn (2) and Ni (3)] were synthesized and their structures were solved by single crystal X-ray diffraction methods. Compound 1 crystallises in orthorhombic system, space group Pc2(1)b with a = 6.9997(4) angstrom, b = 16.4260(9) angstrom, c = 20.3312(18) angstrom, V = 476.30(15) angstrom(3) and Z = 4. Compounds 2 and 3 crystallize in the monoclinic system, space group C2/m with a = 7.3778(4) angstrom, b = 20.1493(6) angstrom, c = 10.4963(4) angstrom, beta = 103.466(8)degrees, V = 1517.5(11) angstrom(3) and Z = 2 for 1 and a = 7.2862(4) angstrom, b = 20.1165(7) angstrom, c = 10.4032(3) angstrom, beta = 103.366(9)degrees, V = 1483.52(11) angstrom(3) and Z = 2 for 2. The structure of 1 consists of layers of four crystallographically independent sodium atoms [two six- (Na(O-w)(6)) and two five- (Na(O-w)(3)O-2) coordinated] which are bridged by tetrakismonodentate bta 42 ligands and single and double water molecules. These layers are interlinked through hydrogen bonds involving some of the coordinated water molecules and free carboxylate-oxygen atoms to afford a 3-D network. Compounds 2 and 3 are isostructural: their structures are made up of chains with regular alternating pairs of Na+ and single M2+ cations [M5Mn (2) and Ni (3)], two water molecules acting as bridges between each pair of metal ions. Two water molecules (at M) and two carboxylate-oxygen atoms from two H(2)bta 22 ligands (at Na) which are coordinated to the metal ions in trans positions build distorted octahedral surroundings. The H(2)bta 22 group acts as a bismonodentate ligand toward adjacent sodium atoms through 1,3-carboxylate oxygens. These neutral chains are interlinked through hydrogen bonds involving free carboxylate-oxygen atoms and coordinated and crystallization water molecules to afford a 3-D structure. |
BibTeX:
@article{ISI:000237785000009,
author = {Fabelo, O and Canadillas-Delgado, L and Pasan, J and Ruiz-Perez, C and Julve, M},
title = {Influence of the presence of divalent first-row transition metal ions on the structure of sodium(I) salts of 1,2,3,4-benzenetetracarboxylic acid (H(4)bta)},
journal = {CRYSTENGCOMM},
year = {2006},
volume = {8},
number = {4},
pages = {338-345},
doi = {{10.1039/b516806f}}
}
|
| Fabelo, O., Canadillas-Delgadot, L., Pasan, J., Delgado, F.S., Lloret, F., Cano, J., Julve, M. & Ruiz-Perez, C. ({2009}), "Study of the Influence of the Bridge on the Magnetic Coupling in Cobalt(II) Complexes" , INORGANIC CHEMISTRY. , DEC 7, {2009}. Vol. {48} ({23}) , pp. {11342-11351}. |
| Abstract: Two new cobalt(II) complexes of formula [Co-2(bta)(H2O)(6)](n)center dot 2nH(2)O (1) and [Co(phda)(H2O)](n)center dot nH(2)O (2) [H(4)bta = 1,2,4,5-benzenetetracarboxylic acid, H(2)phda = 1,4-phenylenediacetic acid] have been characterized by single crystal X-ray diffraction. Compound 1 is a one-dimensional compound where the bta(4-) ligand acts as 2-fold connector between the cobalt(II) ions through two carboxylate groups in para-conformation. Triply bridged dicobalt(II) units occur within each chain, a water molecule, a carboxylate group in the syn-syn conformation, and an oxo-carboxylate with the mu O-2(1);kappa O-2(1),O(2) coordination mode acting as bridges. Compound 2 is a three-dimensional compound, where the phda(2-) group acts as a bridge through its two carboxylate groups, one of them adopting the mu-O,O' coordination mode in the syn-syn conformation and the other exhibiting the single mu(2)-O `' bridging mode. As in 1, chains of cobalt(H) ions occur in 2 with a water molecule, a syn-syn carboxylate group, and an oxo-carboxylate constitute the triply intrachain bridging skeleton. Each chain is linked to other four ones through the phda(2-) ligand, giving rise to the three-dimensional structure, The values of the intrachain cobalt-cobalt separation are 3.1691(4) (1) and 3.11499(2) angstrom (2) whereas those across the phenyl ring of the extended bta(4-) (1) and phda(2-) (2) groups are 10.1120(6) and 11.4805(69 angstrom, respectively. The magnetic properties of 1 and 2 have been investigated in the temperature range 1.9-300 K, and their analysis has revealed the occurrence of moderate intrachain ferromagnetic couplings [J = +5.4 (1) and +2.16 cm(-1) (2), J being the isotropic magnetic coupling parameter], the magnetic coupling through the extended bta(4-) and phda(2-) with cobalt-cobalt separations larger than 10 angstrom being negligible. The nature and magnitude of the magnetic interactions between the high-spin cobalt(II) ions in 1 and 2 are compared to those of related systems and discussed as a function of the complementarity- countercomplementarity effects of the triple bridges. |
BibTeX:
@article{ISI:000272037500066,
author = {Fabelo, Oscar and Canadillas-Delgadot, Laura and Pasan, Jorge and Delgado, Fernando S. and Lloret, Francesc and Cano, Joan and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Study of the Influence of the Bridge on the Magnetic Coupling in Cobalt(II) Complexes},
journal = {INORGANIC CHEMISTRY},
year = {2009},
volume = {48},
number = {23},
pages = {11342-11351},
doi = {{10.1021/ic901843r}}
}
|
| Fabelo, O., Pasan, J., Canadillas-Delgado, L., Delgado, F.S., Labrador, A., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2008}), "(4,4) Rectangular Lattices of Cobalt(II) with 1,2,4,5-Benzenetetracarboxylic Acid: Influence of the Packing in the Crystal Structure" , CRYSTAL GROWTH & DESIGN. , NOV, {2008}. Vol. {8} ({11}) , pp. {3984-3992}. |
| Abstract: The preparation, structural characterization and magnetic investigation of three new cobalt(II) complexes of formula [Co-2(bta)(H2O)(8)](n)center dot 4nH(2)O (1 and 2) and [Co-2(bta)(H2O)(8)](n)center dot 2nH(2)O (3) (H(4)bta = 1,2,4,5-benzenetetracarboxylic acid) are reported. The crystal structures of 1-3 consist of neutral square-grids of high-spin cobalt(II) ions with the fully deprotonated bta(4-) anion acting as a 4-fold connector. The interpenetration of two of these layers in 3 leads to a three-dimensional network. Each cobalt atom in 1-3 is six-coordinated with two carboxylate-oxygen atoms from two bta ligands in trans positions and four water molecules building somewhat distorted octahedral surroundings. Extensive hydrogen bonding involving the noncoordinated carboxylate-oxygens and the coordinated and crystallization water molecules afford three-dimensional supramolecular networks in all three compounds. The values of the intralayer cobalt-cobalt separations through cis- and trans-coordinated carboxylate groups are 6.6831(16) and 11339(2) angstrom for 1, and 6.682(4) and 11.329(5) angstrom for 2 and 6.7801(5)/6.7705(3) and 11.3923(4)/11.2952(3) angstrom for (3). Magnetic susceptibility measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of very weak antiferromagnetic interactions between the high-spin cobalt(II) ions, the strong decrease of chi T-M upon cooling being mainly due to the depopulation of the higher Kramers doublets of the six-coordinated cobalt(II) ions. |
BibTeX:
@article{ISI:000260675500023,
author = {Fabelo, Oscar and Pasan, Jorge and Canadillas-Delgado, Laura and Delgado, Fernando S. and Labrador, Ana and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {(4,4) Rectangular Lattices of Cobalt(II) with 1,2,4,5-Benzenetetracarboxylic Acid: Influence of the Packing in the Crystal Structure},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2008},
volume = {8},
number = {11},
pages = {3984-3992},
doi = {{10.1021/cg800067k}}
}
|
| Fabelo, O., Pasan, J., Canadillas-Delgado, L., Delgado, F.S., Labrador, A., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2008}), "Well-resolved unusual alternating cyclic water tetramers embedded in a crystal host" , CRYSTENGCOMM. Vol. {10} ({12}) , pp. {1743-1746}. |
| Abstract: Infinite network involving two hydrogen-bonded tetrameric water rings (S-4 and D-2h) in a (4,4)-square grid crystal host. |
BibTeX:
@article{ISI:000261170800007,
author = {Fabelo, Oscar and Pasan, Jorge and Canadillas-Delgado, Laura and Delgado, Fernando S. and Labrador, Ana and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Well-resolved unusual alternating cyclic water tetramers embedded in a crystal host},
journal = {CRYSTENGCOMM},
year = {2008},
volume = {10},
number = {12},
pages = {1743-1746},
doi = {{10.1039/b810605c}}
}
|
| Fabelo, O., Pasan, J., Canadillas-Delgado, L., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2009}), "Cobalt(II) Sheet-Like Systems Based on Diacetic Ligands: from Subtle Structural Variances to Different Magnetic Behaviors" , INORGANIC CHEMISTRY. , JUL 6, {2009}. Vol. {48} ({13}) , pp. {6086-6095}. |
| Abstract: (4,4) Layered or pillared-layered Co(II)-complexes demonstrated that small structural modifications may cause important differences in the magnetic behavior of similar systems. |
BibTeX:
@article{ISI:000267507400061,
author = {Fabelo, Oscar and Pasan, Jorge and Canadillas-Delgado, Laura and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Cobalt(II) Sheet-Like Systems Based on Diacetic Ligands: from Subtle Structural Variances to Different Magnetic Behaviors},
journal = {INORGANIC CHEMISTRY},
year = {2009},
volume = {48},
number = {13},
pages = {6086-6095},
doi = {{10.1021/ic9004483}}
}
|
| Fabelo, O., Pasan, J., Canadillas-Delgado, L., Delgado, F.S., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2008}), "Crystal structure and magnetic properties of two isomeric three-dimensional pyromellitate-containing cobalt(II) complexes" , INORGANIC CHEMISTRY. , SEP 15, {2008}. Vol. {47} ({18}) , pp. {8053-8061}. |
| Abstract: The hydrothermal preparation, crystal structure determination, and magnetic study of two isomers made up of 1,2,4,5-benzenetetracarboxylate and high-spin Co-II ions of formula [Co-2(bta)(H2O)(4)]n center dot 2nH(2)O (1 and 2; H(4)bta = 1,2,4,5-benzenetetracarboxylic acid) are reported. 1 and 2 are three-dimensional compounds whose structures can be described as (4,4) rectangular layers of trans-diaquacobalt(II) units with the bta(4-) anion acting as tetrakis-moncidentate ligand through the four carboxylate groups, which are further connected through other trans-[Co(H2O)(2)](2+) (1) and planar [Co(H2O)(4)](2+) (2) entities, with the bridging units being a carboxylate group in either the anti-syn (1) or syn-syn (2) conformations and a water molecule (2). The study of the magnetic properties of 1 and 2 in the temperature range 1.9-300 K shows the occurrence of weak antiferromagnetic interactions between the high-spin Coll ions, with the strong decrease of chi T-M upon cooling being mainly due to the depopulation of the higher energy Kramers doublets of the six-coordinated Coll ions. The computed values of the exchange coupling between the Coll ions across anti-syn carboxylate (1) and syn-syn carboxylate/water (2) bridges are J = -0.060 (1) and -1.90 (2) cm(-1) (with the Hamiltonian being defined as (H) over cap = -J Sigma(i,j)(S) over cap (i)center dot(S) over cap (j)). These values follow the different conformations of the carboxylate bridge in 1 (anti-syn) and 2 (syn-syn) with the occurrence of a double bridge in 2 (water/carboxylate). |
BibTeX:
@article{ISI:000259093700021,
author = {Fabelo, Oscar and Pasan, Jorge and Canadillas-Delgado, Laura and Delgado, Fernando S. and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Crystal structure and magnetic properties of two isomeric three-dimensional pyromellitate-containing cobalt(II) complexes},
journal = {INORGANIC CHEMISTRY},
year = {2008},
volume = {47},
number = {18},
pages = {8053-8061},
doi = {{10.1021/ic800704y}}
}
|
| Fabelo, O., Pasan, J., Canadillas-Delgado, L., Delgado, F.S., Yuste, C., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2009}), "Novel cobalt(II) coordination polymers based on 1,2,4,5-benzenetetracarboxylic acid and extended bis-monodentate ligands" , CRYSTENGCOMM. Vol. {11} ({10}) , pp. {2169-2179}. |
| Abstract: Four new high-spin cobalt(II) complexes of formulae [Co-2(bta)(4,4'-bpy)(2)(H2O)(2)](n) (1), Hbpe[Co(Hbta)(bpe)(H2O)(2)](n) (2), [Co(H(2)bta)(azpy)(H2O)2]. azpy n (3) and [Co-2(bta)(bpa)(2)(H2O)(4)]. 8H(2)O(n) (4) with H4bta - 1,2,4,5-benzenetetracarboxylic acid, 4,4'-bpy 4,4'-bipyridine, bpe = trans-1,2-bis(4-pyridyl) ethene, azpy = 4,4'-azobispyridine and bpa trans-1,2-bis(4-pyridyl) ethane, have been prepared and characterized by single crystal X-ray diffraction. Compounds 1 - 4 exhibit two- dimensional networks where the fully (1 and 4) or partially (2 and 3) deprotonated tetracarboxylic ligand connects two (2 and 3) or four (1 and 4) cobalt( II) ions through two trans-carboxylate (1-3) or all the carboxylate groups (4) whereas the co-ligands 4,4'-bpy (1), bpe (2), azpy (3) and bpa (4) act as two- fold connectors in trans-(bpe and azpy) and gauche-(bpa) conformations. The cobalt( II) ions in 1 are five-coordinated with two nitrogen atoms from two 4,4'-bpy ligands in the axial positions and a water molecule and two carboxylate-oxygens building the trigonal plane. Six-coordinated cobalt( II) ions occur in 2 - 4 with two pyridyl-nitrogen atoms, two carboxylate-oxygens and two trans- coordinated water molecules in a somewhat distorted octahedral surrounding. The magnetic properties of 1 - 4 have been investigated in the temperature range 1.9-300 K. Compound 1 shows a weak antiferromagnetic interaction between the five-coordinated cobalt(II) ions ( 0.13 <= vertical bar J broken vertical bar <= 0.28 cm(-1), (H) over cap = -J (S) over cap (1) . (S) over cap (2)), the exchange pathway involved being the double carboxylate bridges in the syn-syn conformation [ cobalt - cobalt separation] of 3.6465(9) angstrom. As the magnetic interactions between the cobalt( II) ions through the phenyl ring of the bta group in 2-4 and those across the extended bpe (2), azpy ( 3) and bpa ( 4) bridges are negligible, the strong decrease of chi T-M upon cooling observed for 2-4 is mainly due to the depopulation of the higher Kramer doublets of the six-coordinated cobalt( II) ions. |
BibTeX:
@article{ISI:000269799400021,
author = {Fabelo, Oscar and Pasan, Jorge and Canadillas-Delgado, Laura and Delgado, Fernando S. and Yuste, Consuelo and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Novel cobalt(II) coordination polymers based on 1,2,4,5-benzenetetracarboxylic acid and extended bis-monodentate ligands},
journal = {CRYSTENGCOMM},
year = {2009},
volume = {11},
number = {10},
pages = {2169-2179},
doi = {{10.1039/b907895a}}
}
|
| Fabelo, O., Pasan, J., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2008}), "1,2,4,5-benzenetetracarboxylate- and 2,2 `-bipyrimidine-containing cobalt(II) coordination polymers: Preparation, crystal structure, and magnetic properties" , INORGANIC CHEMISTRY. , MAY 5, {2008}. Vol. {47} ({9}) , pp. {3568-3576}. |
| Abstract: Three new mixed-ligand cobalt(II) complexes of formula [Co-2(H2O)(6)(bta)(bpym)](n)center dot 4nH(2)O (1), [Co-2(H2O)(2)(bta)(bpym)](n) (2), and [Co-2(H2O)(4)(bta)(bpym)](n)center dot 2nH(2)O (3) (bpym = 2,2'-bipyrimidine and H(4)bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized by single crystal X-ray diffraction. 1 is a chain compound of mertriaquacobalt(II) units which are linked through regular alternating bis-bidentate bpym and bis-monodentate bta groups. 2 and 3 are three-dimensional compounds where aquacobalt(II) (2) and cis-diaquacobalt(II) (3) entities are linked by bis-bidentate bpym (2 and 3) and tetrakis- (2 and 3) and octakis-monodentate (2) bta ligands. The cobalt atoms in 1-3 exhibit somewhat distorted octahedral surroundings. Two bpym-nitrogen atoms (1-3) and either two bta-oxygens (2) or one bta-oxygen and a water molecule (1 and 3) build the equatorial plane, whereas the axial positions are filled either by two water molecules (1) or by a bta-oxygen atom and a water molecule (2 and 3). The values of the cobalt-cobalt separation across the bridging bpym vary in the range 5.684(2)-5.7752(7) angstrom, whereas those through the bta bridge cover the ranges 5.288(2)-5.7503(5) angstrom (across the anti-syn carboxylate) and 7.715(3)-11.387(1) angstrom (across the phenyl ring). The magnetic properties of 1-3 have been investigated in the, temperature range 1.9-290 K They are all typical of an overall antiferromagnetic coupling with the maxima of the magnetic susceptibility at 14.5 (1) and 11.5 K (2 and 3). Although exchange pathways through bis-bidentate bpym and carboxylate-bta in different coordination modes are involved in 1-3, their magnetic behavior is practically governed by that across the bpym bridge, the magnitude of the exchange coupling being J = -5.59(2) (1), -4.41(2) (2), and -4.49(2) (3) with the Hamiltonian (H) over cap = -J (S) over cap (1)(S) over cap (2). |
BibTeX:
@article{ISI:000255380500021,
author = {Fabelo, Oscar and Pasan, Jorge and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {1,2,4,5-benzenetetracarboxylate- and 2,2 `-bipyrimidine-containing cobalt(II) coordination polymers: Preparation, crystal structure, and magnetic properties},
journal = {INORGANIC CHEMISTRY},
year = {2008},
volume = {47},
number = {9},
pages = {3568-3576},
doi = {{10.1021/ic702187k}}
}
|
| Fabelo, O., Pasan, J., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2007}), "Structural versatility in cobalt(II) complexes with 1,2,4,5-benzene-tetracarboxylic acid (H(4)bta) and 4,4'-bipyridine-N,N'-dioxide (dpo)" , CRYSTENGCOMM. Vol. {9} ({9}) , pp. {815-827}. |
| Abstract: Four new high-spin cobalt(II) complexes of formula [Co( H2O)(6)]( H(2)bta)center dot dpo center dot 4H(2)O ( 1), [Co( H2O) (4)( dpo) (2)( bta)]center dot 4H(2)O center dot( 2), [ Co( H2O) (2))( dpo) 2( H(2)bta)] (n) ( 3) and [ Co( H2O) (3)( dpo)( bta) 1/2](n) (4) ( H(4)bta = 1,2,4,5- benzenetetracarboxylic acid and dpo = 4,4'- bipyridine- N,N'-dioxide)have been synthesized and their structures solved by single crystal X-ray diffraction methods. Compound 1 is an ionic salt whose structure is made up of [ Co( H2O)(6)](2+) cations, H(2)bta(2-) anions, uncoordinated dpo groups and crystallization water molecules, which are linked by extensive hydrogen bonds to afford a three-dimensional network. The structure of 2 consists of bta-bridged dinuclear cobalt( II) complexes where four coordinated water molecules and a terminally bound dpo ligand complete the six coordination around each cobalt atom. The bta ligand in 2 adopts the bis-monodentate bridging mode through two trans carboxylate-oxygen atoms, the intramolecular cobalt-cobalt distance being 11.46(2) angstrom. The structure of 3 is constituted by uniform chains of cobalt( II) ions bridged by the dideprotonated H(2)bta(2-) species through two trans carboxylate-oxygen atoms. Two coordinated water molecules and two terminally bound dpo ligands achieve the six coordination around each cobalt atom. The intrachain cobalt-cobalt separation is 11.387( 1) angstrom. The structure of 4 consists of corrugated layers of cobalt( II) ions bridged by bismonodentate dpo and bta 42 ligands, ( through two trans carboxylate-oxygen atoms), three coordinated water molecules in a fac arrangement achieving the six-coordination around each cobalt atom. The investigation of the magnetic behaviour of 2-4 in the temperature range 1.9-300 K shows the occurrence of very weak antiferromagnetic interactions between the high-spin cobalt( II) ions, the strong decrease of T-xM upon cooling which is observed for this family of complexes ligands being mainly due to the depopulation of the higher energy Kramers doublets of the high-spin octahedral cobalt( II) centers. |
BibTeX:
@article{ISI:000249078700025,
author = {Fabelo, Oscar and Pasan, Jorge and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Structural versatility in cobalt(II) complexes with 1,2,4,5-benzene-tetracarboxylic acid (H(4)bta) and 4,4'-bipyridine-N,N'-dioxide (dpo)},
journal = {CRYSTENGCOMM},
year = {2007},
volume = {9},
number = {9},
pages = {815-827},
doi = {{10.1039/b706035c}}
}
|
| Fejer, S.N., James, T.R., Hernandez-Rojas, J. & Wales, D.J. ({2009}), "Energy landscapes for shells assembled from pentagonal and hexagonal pyramids" , PHYSICAL CHEMISTRY CHEMICAL PHYSICS. Vol. {11} ({12}) , pp. {2098-2104}. |
| Abstract: We present new rigid body potentials that should favour efficient self-assembly of pentagonal and hexagonal pyramids into icosahedral shells over a wide range of temperature. By adding an extra repulsive site opposite the existing apex sites of the pyramids considered in a previously published model, frustrated energy landscapes are transformed into systems identified with self-assembling properties. The extra interaction may be considered analogous to a hydrophobic-hydrophilic repulsion, as in micelle formation. |
BibTeX:
@article{ISI:000264097700023,
author = {Fejer, Szilard N. and James, Tim R. and Hernandez-Rojas, Javier and Wales, David J.},
title = {Energy landscapes for shells assembled from pentagonal and hexagonal pyramids},
journal = {PHYSICAL CHEMISTRY CHEMICAL PHYSICS},
year = {2009},
volume = {11},
number = {12},
pages = {2098-2104},
doi = {{10.1039/b818062h}}
}
|
| Ferrando-Soria, J., Castellano, M., Yuste, C., Lloret, F., Julve, M., Fabelo, O., Ruiz-Perez, C., Stiriba, S.-E., Ruiz-Garcia, R. & Cano, J. ({2010}), "Long-distance magnetic coupling in dinuclear copper(II) complexes with oligo-para-phenylenediamine bridging ligands" , INORGANICA CHIMICA ACTA. , MAY 5, {2010}. Vol. {363} ({8}) , pp. {1666-1678}. |
| Abstract: Two novel dinuclear copper(II) complexes of formulae [Cu-2(tren)(2)(bpda)](ClO4)(4) (2) and [Cu-2(tren)(2)(tpda)]( ClO4) 4 (3) containing the tripodal tris(2-aminoethyl) amine (tren) terminal ligand and the 4,4'-biphenylenediamine (bpda) and 4,4 `'-p-terphenylenediamine (tpda) bridging ligands have been synthesized and structurally, spectroscopically, and magnetically characterized. Their experimentally available electronic spectroscopic and magnetic properties have been reasonably reproduced by DFT and TDDFT calculations. Single crystal X-ray diffraction analysis of 2 shows the presence of dicopper(II) cations where the bpda bridging ligand adopts a bismonodentate coordination mode toward two [Cu(tren)](2+) units with an overall non-planar, orthogonal anti configuration of the N-Cu-N threefold axis of the trigonal bipyramidal Cu-II ions and the biphenylene group. The electronic absorption spectra of 2 and 3 in acetonitrile reveal the presence of four moderately weak d-d transitions characteristic of a slightly distorted trigonal bipyramid stereochemistry of the Cu-II ions. TDDFT calculations on 2 identify these transitions as those taking place between the four lower-lying, doubly occupied a(2) (d(yz))(2), b(2) (d(xz))(2), b(1) (d(xy))(2), and a(1) (d(x2-y2))(2) orbitals and the upper, singly occupied a(1)(d(z2))(1) orbital of each trigonal bipyramidal CuII ion. Variable-temperature magnetic susceptibility measurements of 2 and 3 show the occurrence of moderate (J = -8.5 cm(-1))to weak intramolecular antiferromagnetic couplings (J = -2.0 cm(-1)) [H = -JS(1)center dot S-2 with S-1 = S-2 = S-Cu = 1/2] inspite of the relatively large copper-copper separation across the para-substituted biphenylene- r = 12.3 angstrom) and terphenylenediamine (r = 16.4 angstrom) bridges, respectively. DFT calculations on 2 and 3 support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the dz2 orbital of each trigonal bipyramidal Cu-II ion through the predominantly p-type orbital pathway of the oligo-p-phenylenediamine bridges, as reported earlier for the parent compound [Cu-2(tren)(2)(ppda)](ClO4)(4)center dot 2H(2)O (1) with the 1,4-phenylenediamine (ppda) bridging ligand. Finally, a rather slow exponential decay of the antiferromagnetic coupling (-J) with the number of phenylene repeat units, -(C6H4)(n)-(n = 1-3), has been found both experimentally and theoretically along this series of oligo-p-phenylenediamine-bridged dicopper(II) complexes. These results further support the ability of linear p-conjugated oligo-p-phenylene spacers to transmit the exchange interaction between the unpaired electrons of the two Cu-II centers with intermetallic distances in the range of 7.5-16.4 angstrom. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000276818400007,
author = {Ferrando-Soria, Jesus and Castellano, Maria and Yuste, Consuelo and Lloret, Francesc and Julve, Miguel and Fabelo, Oscar and Ruiz-Perez, Catalina and Stiriba, Salah-Eddine and Ruiz-Garcia, Rafael and Cano, Joan},
title = {Long-distance magnetic coupling in dinuclear copper(II) complexes with oligo-para-phenylenediamine bridging ligands},
journal = {INORGANICA CHIMICA ACTA},
year = {2010},
volume = {363},
number = {8},
pages = {1666-1678},
doi = {{10.1016/j.ica.2009.12.007}}
}
|
| Ferrando-Soria, J., Pardo, E., Ruiz-Garcia, R., Cano, J., Lloret, F., Julve, M., Journaux, Y., Pasan, J. & Ruiz-Perez, C. ({2011}), "Synthesis, Crystal Structures and Magnetic Properties of (MCuII)-Cu-II Chains (M=Mn and Co) with Sterically Hindered Alkyl-Substituted Phenyloxamate Bridging Ligands" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {17} ({7}) , pp. {2176-2188}. |
| Abstract: A series of neutral oxamato-bridged heterobimetallic chains of general formula [MCu(L-x)(2)(S)(2)]center dot p S center dot qH(2)O [p=0-1, q=0-2.5; L-1=N-2,6-dimethylphenyloxamate, S=DMF with M=Mn (1a) and Co (1b); L-2=N-2,6-diethylphenyloxamate, S=DMF with M=Mn (2a) and Co (2b) or S=DMSO with M=Mn (2c) and Co (2d); L-3=N-2,6-diisopropylphenyloxamate, S=DMF with M=Mn (3a) and Co (3b) or S=DMSO with M=Mn (3c) and Co (3d)] were prepared by treating the corresponding anionic oxamatocopper(II) complexes [Cu(L-x)(2)](2-) (x=1-3) with M2+ cations (M=Mn and Co) in DMF or DMSO as the solvent. The single-crystal X-ray structures of 2a and 3a reveal the occurrence of well-isolated, zigzag, oxamato-bridged manganese(II)-copper(II) chains. The intrachain Cu center dot center dot center dot Mn distances across the oxamato bridge are 5.3761(7) and 5.4002(17) angstrom for 2a and 3a, respectively, whereas the shortest interchain Mn center dot center dot center dot Mn distances are 9.4475(16) and 8.1649(14) angstrom for 2a and 3a, respectively. All of these (MCuII)-Cu-II chains (M=Mn and Co) exhibit ID ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling between the square-planar Cu-II and octahedral high-spin M-II ions across the oxamato bridge [-J=31.4-35.2 and 33.4-44.8 cm(-1), respectively; H=Sigma(i)-JS(M,i)(S-Cu,S-i+S-Cu,S-i-1)]. Only the (CoCuII)-Cu-II chains show slow magnetic relaxation effects characteristic of single-chain magnets (SCMs). Analysis of the magnetic relaxation dynamics of 3d shows a thermally activated mechanism (Arrhenius law dependence) with values of the pre-exponential factor (tau(0)=2.6 x 10(-9) s) and activation energy (E-a = 7.7 cm(-1)) that are typical of SCMs. In contrast, two relaxation regimes are observed for 2d in different temperature regions (tau(0) = 3.2 x 10(-10) s and E-a = 24.7 cm(-1) for T < 4.5 K and tau(0)=3.2 x 10(-14) s and E-a = 37.5 cm(-1) for T > 4.5 K). |
BibTeX:
@article{ISI:000287986500019,
author = {Ferrando-Soria, Jesus and Pardo, Emilio and Ruiz-Garcia, Rafael and Cano, Joan and Lloret, Francisco and Julve, Miguel and Journaux, Yves and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Synthesis, Crystal Structures and Magnetic Properties of (MCuII)-Cu-II Chains (M=Mn and Co) with Sterically Hindered Alkyl-Substituted Phenyloxamate Bridging Ligands},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2011},
volume = {17},
number = {7},
pages = {2176-2188},
doi = {{10.1002/chem.201002110}}
}
|
| Gaburro, Z., Oton, C., Ghulinyan, M., Pancheri, L., Pavesi, L. & Capuj, N. ({2005}), "Role of microstructure and layer thickness in porous silicon conductometric gas sensors" , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. , JUN, {2005}. Vol. {202} ({8}) , pp. {1467-1471}. Note:4th International Conference on Porous Semiconductors - Science and Technology (PSST-2004), Cullera, SPAIN, MAR 14-19, 2004. |
| Abstract: The electrical injection in porous silicon fabricated with heavily doped p-type silicon is very sensitive to NO2. The known effect is an injection increase associated to NO2. We show experimentally a strong correlation between two structural properties and the sensitivity of electrical injection to NO2. The first property is the microstructure, i.e. the pore morphology at nm scale. A structure with straight, elongated pores shows large sensitivity, as opposed to a branching structure. The second property is the layer thickness, which determines the sign of the effect of NO2. If the thickness is sufficiently low - of the order of few mu m - the injection in presence of NO2 decreases, instead of increasing. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
BibTeX:
@article{ISI:000230206900027,
author = {Gaburro, Z and Oton, CJ and Ghulinyan, M and Pancheri, L and Pavesi, L and Capuj, N},
title = {Role of microstructure and layer thickness in porous silicon conductometric gas sensors},
journal = {PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE},
year = {2005},
volume = {202},
number = {8},
pages = {1467-1471},
note = {4th International Conference on Porous Semiconductors - Science and Technology (PSST-2004), Cullera, SPAIN, MAR 14-19, 2004},
doi = {{10.1002/pssa.200461138}}
}
|
| Gilliland, S., Pellicer-Porres, J., Segura, A., Munoz, A., Rodriguez-Hernandez, P., Kim, D., Lee, M.S. & Kim, T.Y. ({2007}), "Electronic structure of CuAIO(2) and CUScO2 delafossites under pressure" , PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS. , JAN, {2007}. Vol. {244} ({1}) , pp. {309-314}. Note:12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006. |
| Abstract: The electronic structure of CuAlO2 and CuScO2 delafossites is investigated by means of optical absorption measurements under pressure and ab initio band structure calculations. Measurements are carried out on CuAlO2 monocrystals and pulsed laser deposited CuAlO2 and CuScO2 thin films up to 20 GPa. CuAlO2 is an indirect semiconductor that is stable in the pressure range explored here. The pressure coefficients of the indirect and direct gaps are found to be 15 meV/GPa and 2 meV/GPa respectively. CuScO2 is a direct semiconductor and the pressure coefficient of the excitonic peak energy is -5.5 meV/GPa. Two reversible phase transitions are observed in CuScO2. At 13 GPa the delafossite structure becomes unstable and an unidentified intermediate high pressure phase is observed, which coexists with the delafossite phase up to 18 GPa. The intermediate phase is also a wide gap semiconductor, with an step-like absorption edge at the energy of 3.42 +/- 0.02 eV at 14.0 GPa and a positive pressure coefficient. Above 18 GPa, the absorption edge becomes structureless and its form seems to be that of an indirect gap. In the downstroke, the same sequence of changes is observed, with a hysteresis of about 4 GPa, confirming the structural nature of the transitions. These results are interpreted in the light of theoretical ab initio band structure calculations. |
BibTeX:
@article{ISI:000243693600055,
author = {Gilliland, S. and Pellicer-Porres, J. and Segura, A. and Munoz, A. and Rodriguez-Hernandez, P. and Kim, D. and Lee, M. S. and Kim, T. Y.},
title = {Electronic structure of CuAIO(2) and CUScO2 delafossites under pressure},
journal = {PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS},
year = {2007},
volume = {244},
number = {1},
pages = {309-314},
note = {12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006},
doi = {{10.1002/pssb.200672505}}
}
|
| Gilliland, S., Sanchez-Royo, J.F., Pellicer-Porres, J., Segura, A., Munoz, A., Rodriguez-Hernandez, P. & Lopez-Solano, J. ({2008}), "Electronic structure of p-type ultraviolet-transparent conducting CUScO2 films" , THIN SOLID FILMS. , FEB 15, {2008}. Vol. {516} ({7}) , pp. {1431-1433}. Note:Symposium on Advances in Transparents Electronics held at the European-Materials-Research-Society Meeting, Nice, FRANCE, MAY 29-JUN 01, 2006. |
| Abstract: We investigate the electronic structure of CuSCO2 thin films grown on sapphire and mica substrates by pulsed laser deposition. X-ray diffraction and microanalysis confirm that the films have the expected delafossite crystal structure and stoichiometric proportions. The electronic structure is investigated by means of X-ray and ultraviolet photoelectron spectroscopy. Electronic states in the range 0-1350 eV are identified, making reference to theoretical density-of-states calculations up to 80 eV Photoelectron spectra near the Fermi energy confirm the p-character of the films. Optical absorption spectroscopy shows that the films are transparent up to 3.7 eV and exhibit an intense excitonic peak, with a direct gap energy of 4.24 +/- 0.05 eV at room temperature. Ab initio band structure calculations confirm the direct character of CUSCO2 and allow for an assignment of the direct gap to an electronic transition at the L point of the rhombohedral Brillouin zone. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000253830300026,
author = {Gilliland, S. and Sanchez-Royo, J. F. and Pellicer-Porres, J. and Segura, A. and Munoz, A. and Rodriguez-Hernandez, P. and Lopez-Solano, J.},
title = {Electronic structure of p-type ultraviolet-transparent conducting CUScO2 films},
journal = {THIN SOLID FILMS},
year = {2008},
volume = {516},
number = {7},
pages = {1431-1433},
note = {Symposium on Advances in Transparents Electronics held at the European-Materials-Research-Society Meeting, Nice, FRANCE, MAY 29-JUN 01, 2006},
doi = {{10.1016/j.tsf.2007.03.070}}
}
|
| Gonzalez, B., Hernandez-Rojas, J. & Wales, D. ({2005}), "Global minima and energetics of Li+(H2O), and Ca2+(H2O)(n) clusters for n <= 20" , CHEMICAL PHYSICS LETTERS. , AUG 25, {2005}. Vol. {412} ({1-3}) , pp. {23-28}. |
| Abstract: We present candidate structures for the global potential energy minima of X(H2O)(n) (X = Li+, Ca2+) clusters with n <= 20. The TIP4P rigid body water-water potential is employed, together with cation-water interactions that are represented as a sum of Coulomb and Lennard-Jones terms. We find that in the Li+ global minima the cation tends to be located on the cluster surface with a preferred coordination number of four water molecules in tetrahedral positions. In contrast, for Ca2+ clusters the cation occupies an interior site surrounded by eight water molecules in a square anti-prismatic arrangement. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000231207400005,
author = {Gonzalez, BS and Hernandez-Rojas, J and Wales, DJ},
title = {Global minima and energetics of Li+(H2O), and Ca2+(H2O)(n) clusters for n <= 20},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2005},
volume = {412},
number = {1-3},
pages = {23-28},
doi = {{10.1016/j.cplett.2005.06.090}}
}
|
| Gonzalez, B.S., Hernandez-Rojas, J., Breton, J. & Gomez Llorente, J.M. ({2007}), "Global potential energy minima of (H2O)(n) clusters on graphite" , JOURNAL OF PHYSICAL CHEMISTRY C. , OCT 11, {2007}. Vol. {111} ({40}) , pp. {14862-14869}. |
| Abstract: Likely candidates for the global potential energy minima of (H2O)(n) clusters with n <= 21 on the (0001) surface of graphite are found using basin-hopping global optimization. The potential energy surfaces are constructed using the TIP4P intermolecular potentials for the water molecules (the TIP3P is also explored as a secondary choice), a Lennard-Jones water-graphite potential, and a water-graphite polarization potential that is built from classical electrostatic image methods and takes into account both the perpendicular and the parallel electric polarizations of graphite. This potential energy surface produces a rather hydrophobic water-graphite interaction. As a consequence, the water component of the lowest graphite-(H2O)(n) minima is quite closely related to low-lying minima of the corresponding TIP4P (H2O)(n) clusters. In about half of the cases, the geometrical substructure of the water molecules in the graphite-(H2O)(n) global minimum coincides with that of the corresponding free water cluster. Exceptions occur when the interaction with graphite induces a change in geometry. A comparison of our results with available theoretical and experimental data is performed. |
BibTeX:
@article{ISI:000249986600040,
author = {Gonzalez, B. S. and Hernandez-Rojas, J. and Breton, J. and Gomez Llorente, J. M.},
title = {Global potential energy minima of (H2O)(n) clusters on graphite},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
year = {2007},
volume = {111},
number = {40},
pages = {14862-14869},
doi = {{10.1021/jp074249f}}
}
|
| Gonzalez, B.S., Hernandez-Rojas, J., Breton, J. & Llorente, J.M.G. ({2008}), "Global Potential Energy Minima of (H2O)(n) Clusters on Graphite: A Comparative Study of the TIPNP (N=3, 4, 5) Family" , JOURNAL OF PHYSICAL CHEMISTRY C. , OCT, {2008}. Vol. {112} ({42}) , pp. {16497-16504}. |
| Abstract: The water-graphite interaction potential proposed recently (Gonzalez, B. S.; Hernandez-Rojas, J.; Breton, J.; Gomez Llorente, J. M. J. Phys. Chem. C 2007, 111, 14862), the three TIPNP (N = 3, 4, 5) water-water interaction models, and basin-hopping global optimization are used to find the likely candidates for the global potential energy minima of (H2O)(n) clusters with n <= 21 on the (0001) surface of graphite and to perform a comparative study of these minima. We show that, except for the smaller clusters (n < 6), for which ab initio results are available, the three water-water potential models provide mostly nonequivalent conformations. While TIP3P seems to favor monolayer water structures for n < 18, TIP4P and TIP5P favor bilayer or volume structures for n > 6. These n values determine the threshold of dominance of the hydrophobic nature of the water-graphite interaction at the nanoscopic scale for these potential models. |
BibTeX:
@article{ISI:000260129400056,
author = {Gonzalez, B. S. and Hernandez-Rojas, J. and Breton, J. and Llorente, J. M. Gomez},
title = {Global Potential Energy Minima of (H2O)(n) Clusters on Graphite: A Comparative Study of the TIPNP (N=3, 4, 5) Family},
journal = {JOURNAL OF PHYSICAL CHEMISTRY C},
year = {2008},
volume = {112},
number = {42},
pages = {16497-16504},
doi = {{10.1021/jp803107q}}
}
|
| Gonzalez-Diaz, B., Diaz-Herrera, B., Guerrero-Lemus, R., Mendez-Ramos, J., Rodriguez, V.D., Hernandez-Rodriguez, C. & Martinez-Duart, J.M. ({2008}), "Erbium doped stain etched porous silicon" , MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY. , JAN 15, {2008}. Vol. {146} ({1-3}) , pp. {171-174}. Note:Meeting of the European-Materials-Research-Society, Strasbourg, FRANCE, MAY 28-JUN 01, 2007. |
| Abstract: In this work a simple erbium doping process applied to stain etched porous silicon layers (PSLs) is proposed. This doping process has been developed for application in porous silicon solar cells, where conventional erbium doping processes are not affordable because of the high processing cost and technical difficulties. The PSLs were formed by immersion in a HF/HNO3 solution to properly adjust the porosity and pore thickness to an optimal doping of the porous structure. After the formation of the porous structure, the PSLs were analyzed by means of nitrogen BET (Brunauer, Emmett and Teller) area measurements and scanning electron microscopy. Subsequently, the PSLs were immersed in a saturated erbium nitrate solution in order to cover the porous surface. Then, the samples were subjected to a thermal process to activate the Er 3, ions. Different temperatures and annealing times were used in this process. The photoluminescence of the PSLs was evaluated before and after the doping processes and the composition was analyzed by Fourier transform IR spectroscopy. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000252668300036,
author = {Gonzalez-Diaz, B. and Diaz-Herrera, B. and Guerrero-Lemus, R. and Mendez-Ramos, J. and Rodriguez, V. D. and Hernandez-Rodriguez, C. and Martinez-Duart, J. M.},
title = {Erbium doped stain etched porous silicon},
journal = {MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY},
year = {2008},
volume = {146},
number = {1-3},
pages = {171-174},
note = {Meeting of the European-Materials-Research-Society, Strasbourg, FRANCE, MAY 28-JUN 01, 2007},
doi = {{10.1016/j.mseb.2007.07.020}}
}
|
| Gonzalez-Diaz, B., Guerrero-Lemus, R., Borchert, D., Hernandez-Rodriguez, C. & Martinez-Duart, J.M. ({2007}), "Low-porosity porous silicon nanostructures on monocrystalline silicon solar cells" , PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES. , APR, {2007}. Vol. {38} ({1-2}) , pp. {215-218}. Note:Symposium on Silicon Nanocrystals for Electronic and Sensing Applications held at the 2006 E-MRS Spring Meeting, Nice, FRANCE, MAY 29-JUN 02, 2006. |
| Abstract: In this work we present a study of low-porosity porous silicon (PS) nanostructures stain etched on monocrystalline silicon solar cells. The PS layers reduce the reflectance, improve the diffusion of dopants by rapid thermal processes, and increase the homogeneity of the sheet resistance. Some samples were subjected to chemical oxidation in HNO3 to reduce the porosity of the surface layer. After the diffusion process, deposition of a SiNx, antireflection layer, and screen printing of the samples, an efficiency of 15.5% is obtained for low-porosity PS solar cells, compared with an efficiency of 10.0% for standard PS cells and 14.9% for the reference Cz cells. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000246465000048,
author = {Gonzalez-Diaz, B. and Guerrero-Lemus, R. and Borchert, D. and Hernandez-Rodriguez, C. and Martinez-Duart, J. M.},
title = {Low-porosity porous silicon nanostructures on monocrystalline silicon solar cells},
journal = {PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES},
year = {2007},
volume = {38},
number = {1-2},
pages = {215-218},
note = {Symposium on Silicon Nanocrystals for Electronic and Sensing Applications held at the 2006 E-MRS Spring Meeting, Nice, FRANCE, MAY 29-JUN 02, 2006},
doi = {{10.1016/j.physe.2006.12.042}}
}
|
| Gonzalez-Diaz, B., Guerrero-Lemus, R., Diaz-Herrera, B., Marrero, N., Mendez-Ramos, J. & Borchert, D. ({2009}), "Optimization of roughness, reflectance and photoluminescence for acid textured mc-Si solar cells etched at different HF/HNO3 concentrations" , MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS. , MAR 15, {2009}. Vol. {159-60} ({Sp. Iss. SI}) , pp. {295-298}. Note:Symposium on Advanced Silicon Materials Research for Electronic and Photovoltaic Applications held at the 2008 E-MRS Spring Meeting, Strasbourg, FRANCE, MAY 26-30, 2008. |
| Abstract: The surface structure of multi-crystalline silicon (mc-Si) etched in HF/HNO3 at different HF/HNO3 concentrations is optimized for being applied in solar cells. The resulting texture, which determines the efficiency of solar cells, was characterized by means of scanning electron microscopy (SEM) and optical spectroscopy. The roughness of the surface increases and the reflectance decreases when the content of HNO3 in the etching solution is increased to a limit. The produced etched pits on the surface have been identified by SEM and the surface mean roughness has been characterized by atomic force microscopy (AFM). Also, depending on the concentration of the electrolyte, the mc-Si samples exhibit photoluminescence in the VIS range under UV excitation. The PL reveals the presence of nanocrystals on the surface of the etched samples. The surface structure is also optimized for an adequate placement of the metallic contact on top. Finally the solar cells were performed in order to investigate the dependence of the roughness, reflectance and photoluminescence to the solar efficiency. (c) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000267635500071,
author = {Gonzalez-Diaz, B. and Guerrero-Lemus, R. and Diaz-Herrera, B. and Marrero, N. and Mendez-Ramos, J. and Borchert, Dietmar},
title = {Optimization of roughness, reflectance and photoluminescence for acid textured mc-Si solar cells etched at different HF/HNO3 concentrations},
journal = {MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS},
year = {2009},
volume = {159-60},
number = {Sp. Iss. SI},
pages = {295-298},
note = {Symposium on Advanced Silicon Materials Research for Electronic and Photovoltaic Applications held at the 2008 E-MRS Spring Meeting, Strasbourg, FRANCE, MAY 26-30, 2008},
doi = {{10.1016/j.mseb.2008.11.003}}
}
|
| Gonzalez-Diaz, B., Guerrero-Lemus, R., Haro-Gonzalez, P., Borchert, D. & Hernandez-Rodriguez, C. ({2006}), "Down-conversion properties of luminescent silicon nanostructures formed and passivated in HNO3-based solutions" , THIN SOLID FILMS. , JUL 26, {2006}. Vol. {511} , pp. {473-477}. Note:Symposium on Thin Film and Nanostructured Materials for Photovoltaics held at the 2005 EMRS Meeting, Strasbourg, FRANCE, MAY 31-JUN 03, 2005. |
| Abstract: In this work, photoluminescent porous silicon (PS) stain etched and passivated by means of oxidation in HNO3/H2SO4 or HNO3/H2O2 solutions has been studied. These passivation methods have preserved the PS photoluminescence and also have increased the photocarriers' lifetime, which are required for efficient down-conversion properties. The samples have been characterized by Fourier transform infrared spectroscopy, spectrofluorometry and microwave photoconduction decay. The results show that the photocarriers lifetime and the photoluminescence values are sensitively dependent on the evolution of the Si-H, Si-O and O-H bonds. (c) 2005 Elsevier B.V All rights reserved. |
BibTeX:
@article{ISI:000238249000096,
author = {Gonzalez-Diaz, B and Guerrero-Lemus, R and Haro-Gonzalez, P and Borchert, D and Hernandez-Rodriguez, C},
title = {Down-conversion properties of luminescent silicon nanostructures formed and passivated in HNO3-based solutions},
journal = {THIN SOLID FILMS},
year = {2006},
volume = {511},
pages = {473-477},
note = {Symposium on Thin Film and Nanostructured Materials for Photovoltaics held at the 2005 EMRS Meeting, Strasbourg, FRANCE, MAY 31-JUN 03, 2005},
doi = {{10.1016/j.tsf.2005.12.129}}
}
|
| Gonzalez-Diaz, B., Guerrero-Lemus, R., Marrero, N., Hernandez-Rodriguez, C., Ben-Hander, F. & Martinez-Duart, J. ({2006}), "Anisotropic textured silicon obtained by stain-etching at low etching rates" , JOURNAL OF PHYSICS D-APPLIED PHYSICS. , FEB 21, {2006}. Vol. {39} ({4}) , pp. {631-634}. |
| Abstract: The structure, luminescence and etching kinetics for porous silicon stain-etched at different temperatures are studied. The results reveal that for temperatures below 10 degrees C and for short etching times, a novel anisotropic structure based on surface roughness preferentially oriented in the (100) direction is observed. At temperatures higher than 10 degrees C or large etching times, typical macropores and mesopores with non-preferential pore wall orientation are detected. The luminescence spectra of the samples with preferential surface roughness orientation are red-shifted with respect to the samples with typical isotropic orientation. The results are interpreted in terms of average etching rates and pore growth. |
BibTeX:
@article{ISI:000236103100007,
author = {Gonzalez-Diaz, B and Guerrero-Lemus, R and Marrero, N and Hernandez-Rodriguez, C and Ben-Hander, FA and Martinez-Duart, JM},
title = {Anisotropic textured silicon obtained by stain-etching at low etching rates},
journal = {JOURNAL OF PHYSICS D-APPLIED PHYSICS},
year = {2006},
volume = {39},
number = {4},
pages = {631-634},
doi = {{10.1088/0022-3727/39/4/006}}
}
|
| Gonzalez-Diaz, B., Guerrero-Lemus, R., Mendez-Ramos, J., Diaz-Herrera, B. & Rodriguez, V.D. ({2009}), "Gradual oxidation of stain etched porous silicon nanostructures applied to silicon-based solar cells" , SENSORS AND ACTUATORS A-PHYSICAL. , MAR 16, {2009}. Vol. {150} ({1}) , pp. {97-101}. |
| Abstract: This work describes the photoluminescence (PL) and morphology of stain etched porous silicon nanostructures (PSN) submitted to a gradual oxidation by immersion in a HNO3 boiling point solution and applied to solar cells. The gradual oxidation passivates the extremely reactant fresh porous surface and softens the porous structure for ail adequate placement of the metallic contact on top. The pore size and the porosity of the samples have been evaluated by means of the Brunauer, Emmett and Teller (BET) technique. The surface morphology has been analyzed by atomic forces microscopy. The oxidation process of the layers has been evaluated using a Fourier transform infrared spectrometer (MR), analyzing the evolution of the Si-O, Si-H and Si-OH absorption bands. It is found a blueshift in the PI-spectra attributed to the oxidation process which increases the photoconversion properties of the nanostructures. An efficiency of 15.2% and fill factor (FF) of 80.5% were found. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000264331200011,
author = {Gonzalez-Diaz, B. and Guerrero-Lemus, R. and Mendez-Ramos, J. and Diaz-Herrera, B. and Rodriguez, V. D.},
title = {Gradual oxidation of stain etched porous silicon nanostructures applied to silicon-based solar cells},
journal = {SENSORS AND ACTUATORS A-PHYSICAL},
year = {2009},
volume = {150},
number = {1},
pages = {97-101},
doi = {{10.1016/j.sna.2008.12.006}}
}
|
| Gonzalez-Diaz, B., Mendez-Ramos, J., del Castillo, J., Diaz-Herrera, B., Guerrero-Lemus, R., Hernandez-Rodriguez, C. & Rodriguez, V.D. ({2007}), "The role of the temperature and ageing in the photoluminescence behaviour on porous silicon stain etched films - art. no. 65931P" , In Photonic Materials, Devices, and Applications II. Vol. {6593} , pp. {P5931}. Note:Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007. |
| Abstract: The role of the ageing in the photoluminescence (PL) of stain etched porous silicon (PS) layers and its behaviour at different temperatures have been studied. The photoluminescence has been measured at different temperatures showing the influence of the phonons in the intensity of the emissions and the lifetimes. Two contributions to the photoluminescence spectra have been found: one due to quantum confinement effects and the other one due to the presence of non-bridging oxygen hole centre defects. There is no evidence of energetic shifts on the maximum at different temperatures. |
BibTeX:
@inproceedings{ISI:000250171600053,
author = {Gonzalez-Diaz, B. and Mendez-Ramos, J. and del-Castillo, J. and Diaz-Herrera, B. and Guerrero-Lemus, R. and Hernandez-Rodriguez, C. and Rodriguez, V. D.},
title = {The role of the temperature and ageing in the photoluminescence behaviour on porous silicon stain etched films - art. no. 65931P},
booktitle = {Photonic Materials, Devices, and Applications II},
year = {2007},
volume = {6593},
pages = {P5931},
note = {Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007},
doi = {{10.1117/12.721958}}
}
|
| Gonzalez-Perez, S., Haro-Gonzalez, P. & Martin, I.R. ({2010}), "MICROCRYSTALLIZATION IN OXYFLUORIDE Nd3+ DOPED GLASS DUE TO LASER IRRADIATION" , In CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS. Vol. {210} , pp. {561-565}. Note:9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008. |
| Abstract: A local crystalline formation in a Neodymium doped oxyfluoride glass has been obtained using laser irradiation. It has been studied the intense emission around 880 originated from the F-4(3/2) (Nd3+) level when the glass matrix changes to a glass ceramic structure due to the irradiation of the laser beam. The emission spectra and the lifetime values obtained before and after the irradiation with 1400 mW reveals that the devitrification process made by the laser power beam has been successfully achieved. Moreover, the estimation of the temperature at the local position during irradiation agrees with the temperature of devitrification for these samples. The results confirm that micro-crystals of beta-PbF2 have been created by the laser action and also that the transition from glass to glass ceramic has been completed. These results are in agreement with the bulk spectroscopy measurements. |
BibTeX:
@inproceedings{ISI:000287890200079,
author = {Gonzalez-Perez, S. and Haro-Gonzalez, P. and Martin, I. R.},
title = {MICROCRYSTALLIZATION IN OXYFLUORIDE Nd3+ DOPED GLASS DUE TO LASER IRRADIATION},
booktitle = {CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS},
year = {2010},
volume = {210},
pages = {561-565},
note = {9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008}
}
|
| Gonzalez-Perez, S., Lahoz, F., Caceres, J.M., Lavin, V., da Silva, I., Gonzalez-Platas, J. & Martin, I.R. ({2007}), "Energy transfer in Pr3+-Yb3+ codoped oxyfluoride glass ceramics" , OPTICAL MATERIALS. , JUN, {2007}. Vol. {29} ({10}) , pp. {1231-1235}. Note:1st Laser Ceramic Symposium, Warsaw, POLAND, SEP 05-06, 2005. |
| Abstract: A study of the optical properties of Pr3+-> Yb3+ ions in oxyfluoride glass and glass ceramics was carried out. The cross section emissions at 1300 nm corresponding to the (1)G(4) -> H-3(5) transition of Pr3+ ions were obtained. The ceramming process reduced the linewidth of this transition by about 12% and the emission stimulated cross section was increased by a factor of 1.4 compared to the precursor glasses. The mean wavelength is nearly constant (about 1325 nm) above room temperature. After analyzing the luminescence decay curves of Yb3+ ions, it was found that the majority of the optically active ions in the glass ceramic were located in the fluoride nanocrystals and the rest in the glassy phase. The shortening of distances between the ions turns the energy transfer process into Yb3+ -> Pr-3. However, emission at 1300 nm Pr3+ was concentration quenched. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000247187400004,
author = {Gonzalez-Perez, S. and Lahoz, F. and Caceres, J. M. and Lavin, V. and da Silva, I. and Gonzalez-Platas, J. and Martin, I. R.},
title = {Energy transfer in Pr3+-Yb3+ codoped oxyfluoride glass ceramics},
journal = {OPTICAL MATERIALS},
year = {2007},
volume = {29},
number = {10},
pages = {1231-1235},
note = {1st Laser Ceramic Symposium, Warsaw, POLAND, SEP 05-06, 2005},
doi = {{10.1016/j.optmat.2006.02.022}}
}
|
| Gonzalez-Perez, S., Martin, I.R. & Haro-Gonzalez, P. ({2009}), "Local devitrification on an oxyfluoride glass doped with Ho3+ ions under Argon laser irradiation" , OPTICAL MATERIALS. , JUL, {2009}. Vol. {31} ({9}) , pp. {1373-1375}. Note:2nd International Workshop on Photoluminescence in Rare Earths - Photonic Materials and Devices, Trento, ITALY, MAY 24-25, 2007. |
| Abstract: Devitrification in a holmium-doped oxyfluoride glass has been obtained under laser irradiation. The emissions from S-5(2) (F-5(4)) and F-5(5) levels have been studied in order to analyze structure changes by the irradiation of the laser beam. The emission spectra before and after the irradiation with 2.5 W reveal that the structure of the glass sample has been modified permanently due to the laser action. Time-resolved spectra have been analyzed in the wavelength range 720-780 nm in the glass before and after irradiation, and in glass ceramic bulk samples. Lifetime measurements as a function of the distance to the centre of the damaged zone of the irradiated glass have also been carried out, and the results confirm that the devitrification was achieved Successfully. Moreover, from the analyzes of these results it can be concluded that approximately 70% of the Ho3+ ions are located in the nanocrystals and less than 30% in the glassy phase. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000267837200028,
author = {Gonzalez-Perez, S. and Martin, I. R. and Haro-Gonzalez, P.},
title = {Local devitrification on an oxyfluoride glass doped with Ho3+ ions under Argon laser irradiation},
journal = {OPTICAL MATERIALS},
year = {2009},
volume = {31},
number = {9},
pages = {1373-1375},
note = {2nd International Workshop on Photoluminescence in Rare Earths - Photonic Materials and Devices, Trento, ITALY, MAY 24-25, 2007},
doi = {{10.1016/j.optmat.2008.10.015}}
}
|
| Gonzalez-Perez, S., Martin, I.R., Jaque, D. & Haro-Gonzalez, P. ({2009}), "Growth of Nanocrystals in a Nd3+-Yb3+ Codoped Oxyfluoride Glass by Laser Irradiation" , JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. , JUN, {2009}. Vol. {9} ({6, Sp. Iss. SI}) , pp. {3771-3774}. |
| Abstract: A local nanocrystalline formation in a Neodymium-Ytterbium codoped oxyfluoride glass has been obtained. It has been studied the intense emissions around 880 and 975 nm originated from the F-4(3/2)(Nd3+) and F-2(5/2)(Yb3+) levels when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam. The emission spectra before and after the irradiation with 2900 mW reveals that the desvitrification process made by the laser power beam has been successfully achieved. The intensities and lifetime changes of these levels inside and outside the hole made by the laser damage have been analyzed. These results confirm that nanocrystals of beta PbF2 have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the bulk spectroscopic measurements. |
BibTeX:
@article{ISI:000265794500065,
author = {Gonzalez-Perez, S. and Martin, I. R. and Jaque, D. and Haro-Gonzalez, P.},
title = {Growth of Nanocrystals in a Nd3+-Yb3+ Codoped Oxyfluoride Glass by Laser Irradiation},
journal = {JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY},
year = {2009},
volume = {9},
number = {6, Sp. Iss. SI},
pages = {3771-3774},
doi = {{10.1166/jnn.2009.NS65}}
}
|
| Gonzalez-Perez, S., Martin, I.R., Jaque, D., Haro-Gonzalez, P. & Capuj, N. ({2010}), "Control of the local devitrification on oxyfluoride glass doped with Er3+ ions under diode laser irradiation" , JOURNAL OF APPLIED PHYSICS. , NOV 15, {2010}. Vol. {108} ({10}) |
| Abstract: Temperature control of the devitrification process in an erbium doped oxyfluoride glass under laser irradiation is reported. The green upconversion emissions around 525 and 545 nm originated from the thermalized H-2(11/2) and S-4(3/2) levels were studied when the glass structure changes to glass ceramic during irradiation with a laser beam. Power dependence of the fluorescence intensity ratio was used to determine the temperature of the irradiated zone. The transition from glass to glass ceramic takes place under 2300 mW of laser power with an estimated temperature around 783 K. This result agrees with the one obtained in the samples devitrified under conventional furnace treatment. Therefore, the estimation of the temperature of the irradiated zone through the fluorescence intensity ratio method allows a controlled devitrification. Moreover, an irradiated line has been written in the glass showing an important diffusion of the Pb2+ and F- ions. These results confirm that nanocrystals have been created due to the laser action. (C) 2010 American Institute of Physics. [doi:10.1063/1.3504857] |
BibTeX:
@article{ISI:000285005000018,
author = {Gonzalez-Perez, S. and Martin, I. R. and Jaque, D. and Haro-Gonzalez, P. and Capuj, N.},
title = {Control of the local devitrification on oxyfluoride glass doped with Er3+ ions under diode laser irradiation},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2010},
volume = {108},
number = {10},
doi = {{10.1063/1.3504857}}
}
|
| Gonzalez-Perez, S., Martin, I.R., Lahoz, F., Haro-Gonzalez, P. & Herreros, J. ({2008}), "Local crystallization in an oxyfluoride glass doped with Er3+ ions using a continuous argon laser" , APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING. , DEC, {2008}. Vol. {93} ({4}) , pp. {983-986}. |
| Abstract: Local crystalline formation in erbium doped oxyfluoride glass has been obtained under a cw Argon laser irradiation up to 1.8 W pumping power. By exciting at 514 nm, the emission from 800 nm and 850 nm corresponding to the S-4(3/2)(H-2(11/2))-> I-4(13/2) electronic transitions have been analyzed both inside and outside the irradiated area. The changes in the emission spectra indicate that the high power Ar laser irradiation has resulted in a localized desvitrification process. The temperature dependence of the fluorescence intensity ratio of the 800 nm and 850 nm emission bands has been used to determine the temperature of the irradiated zone. Moreover, the average lifetime of the S-4(3/2)(H-2(11/2)) thermalized levels have been measured as a function of the excitation spot position. An important decrease is observed at the irradiated area. These results confirm that a localized cristalline phase has been created by the laser action. |
BibTeX:
@article{ISI:000260218500028,
author = {Gonzalez-Perez, S. and Martin, I. R. and Lahoz, F. and Haro-Gonzalez, P. and Herreros, J.},
title = {Local crystallization in an oxyfluoride glass doped with Er3+ ions using a continuous argon laser},
journal = {APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING},
year = {2008},
volume = {93},
number = {4},
pages = {983-986},
doi = {{10.1007/s00339-008-4762-1}}
}
|
| Gonzalez-Perez, S., Martin, I.R., Lahoz, F., Jaque, D., Haro-Gonzalez, P. & Capuj, N. ({2008}), "Desvitrification on an oxyfluoride glass doped with Tm3+ and Yb3+ ions under Ar laser irradiation" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {905-907}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: Desvitrification in a Tm3+ and Yb3+ codoped oxyfluoride glass has been obtained by exciting with a continuous Argon laser radiation increasing the average laser power from 144 to 2900 mW. Excitation spectra inside a locally damaged zone in a 1 mol% Tm3+ and 2.5 mol% Yb3+ codoped glass have been measured under excitation in the wavelength range 750-830 nm detecting the F-2(5/2) (Yb3+) level. This curve is the result of the contribution of two different kinds of centers, the fluoride nanocrystals and the glassy phase of the glass ceramic sample created due to the irradiation. The weight of the contributions of each of the centers depends on the excitation wavelength, and from the analysis of the decay of the luminescence it can be concluded that. approximately 80% of the Tm3+ ions are located in the nanocrystals and therefore less than 20% in the glassy phase. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400063,
author = {Gonzalez-Perez, S. and Martin, I. R. and Lahoz, F. and Jaque, D. and Haro-Gonzalez, P. and Capuj, N.},
title = {Desvitrification on an oxyfluoride glass doped with Tm3+ and Yb3+ ions under Ar laser irradiation},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {905-907},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.11.030}}
}
|
| Gonzalez-Perez, S., Martin, I.R., Rivera-Lopez, F. & Lahoz, F. ({2007}), "Temperature dependence of Nd3+-> Yb3+ energy transfer processes in co-doped oxyfluoride glass ceramics" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , JUN 15, {2007}. Vol. {353} ({18-21}) , pp. {1951-1955}. Note:10th International Conference on the Structure of Non-Crystalline Materials (NCM 10), Prague, CZECH REPUBLIC, SEP 18-22, 2006. |
| Abstract: A study of the Nd3+ -> Yb-3 energy transfer processes in transparent oxylluoride glass ceramics has been carried out as a function of temperature in the 100-700 K range. This host is a two-phase optical material that consists of a low-phonon energy fluoride nanocrystalline phase embedded in a predominantly alummosilicate glassy medium and has shown to be an interesting matrix for rare earth ions. Luminescence decay curves of single Nd3+ and Yb3+ doped and co-doped samples at different temperatures have been analyzed in order to calculate the energy transfer and backtransfer rates between these ions. Finally, the results have been also investigated to known the phonons involved in the energy transfer processes, concluding at the end that the Nd3+ -> Yb3+ energy transfer rate takes place by the emission of three phonons with energy around 325 cm(-1) and in the other hand, Nd3+ -> Yb3+ energy transfer rate has been found to be non-negligible for temperatures over 370 K with the requirement of absorption of phonons. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000247330600048,
author = {Gonzalez-Perez, S. and Martin, I. R. and Rivera-Lopez, F. and Lahoz, F.},
title = {Temperature dependence of Nd3+-> Yb3+ energy transfer processes in co-doped oxyfluoride glass ceramics},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2007},
volume = {353},
number = {18-21},
pages = {1951-1955},
note = {10th International Conference on the Structure of Non-Crystalline Materials (NCM 10), Prague, CZECH REPUBLIC, SEP 18-22, 2006},
doi = {{10.1016/j.jnoncrysol.2007.01.059}}
}
|
| Gonzalez-Silgo, C., Torres, M., Lopez, T., Gonzalez-Platas, J., Yanes, A., Del Castillo, J., Peraza, J. & Solans, X. ({2006}), "Thermal dependence of microstructure and electric properties in doped calcium tartrates" , MATERIALS LETTERS. , JUN, {2006}. Vol. {60} ({12}) , pp. {1509-1514}. |
| Abstract: Polycrystalline samples of pure calcium tartrate [CaC(4)H(4)O(6)(.)2H(2)O](.)2H(2)O (labelled CaT) and CaT doped with divalent cations (Sr, Ba, Co, Zn and Cd) were studied using thermal analysis, impedance measurements and X-ray powder diffraction. Cell parameters were calculated for all compounds at six temperatures, in the temperature range 323 to 398 K, by whole-pattern profile matching. Then microstructural parameters were obtained by refining patterns using a pseudo-Voigt function. The ac conductivity of these samples in the frequency range 400 Hz-200 kHz between 338 K and 373 K has been measured. These results show that the conduction mechanisms, thermal stability and microstructure differ, depending on whether the doping agent is earth alkaline or a transition metal. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000236227300017,
author = {Gonzalez-Silgo, C and Torres, ME and Lopez, T and Gonzalez-Platas, J and Yanes, AC and Del Castillo, J and Peraza, JF and Solans, X},
title = {Thermal dependence of microstructure and electric properties in doped calcium tartrates},
journal = {MATERIALS LETTERS},
year = {2006},
volume = {60},
number = {12},
pages = {1509-1514},
doi = {{10.1016/j.matlet.2005.11.068}}
}
|
| Guerrero-Lemus, R., Diaz-Herrera, B. & Manuel Martinez-Duart, J. ({2009}), "Study of the Spanish R&D&I Plan 2004-2007 in energy" , ENERGY POLICY. , NOV, {2009}. Vol. {37} ({11}) , pp. {4779-4786}. |
| Abstract: This paper aims to analyze the public funds transferred to energy projects granted by the Department of Research in the frame of the Spanish Scientific Research, Development and Technological Innovation (R&D&I) Plan 2004-2007. The subjects of the projects granted for R&D activities in incipient technologies and the thematic priorities in energy research covered by the annual calls for proposals are analyzed. In addition, the amount of funds transferred to R&D in energy compared to the rest of research activities promoted by the Spanish Government, the territorial distribution of the research centres granted, the distribution of funds in relation to the technologies granted and the Spanish research centres more active in the diverse energy research areas are presented. (C) 2009 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000271824600060,
author = {Guerrero-Lemus, Ricardo and Diaz-Herrera, Bruno and Manuel Martinez-Duart, Jose},
title = {Study of the Spanish R&D&I Plan 2004-2007 in energy},
journal = {ENERGY POLICY},
year = {2009},
volume = {37},
number = {11},
pages = {4779-4786},
doi = {{10.1016/j.enpol.2009.06.036}}
}
|
| Haro-Gonzalez, P., Bettinelli, M., Capuj, N.E., Lahoz, F., Martin, I.R., Cavalli, E. & Gonzalez-Perez, S. ({2010}), "Optical gain in Er3+-doped transparent LuVO4 crystal at 850 nm" , OPTICAL MATERIALS. , JAN, {2010}. Vol. {32} ({3}) , pp. {475-478}. |
| Abstract: Evidence of a positive optical gain has been observed in an Er3+-doped LuVO4 crystal in a pump and probe experiment. The radiative transition from the S-4(3/2) (H-2(11/2)) level to the I-4(13/2) metastable level of the Er3+ ion gives rise to an intense emission centred at 850 nm. The S-4(3/2)(H-2(11/2)) level of Er3+ ions is populated with high power laser pulses at 532 nm due to the I-4(15/2) -> S-4(3/2)(H-2(11/2)) ground state absorption. The S-4(3/2)(H-2(11/2)) -> I-4(13/2) electronic transition is stimulated with a low signa cw beam at 850 nm. Under these conditions, the high power pump Pulses allowed to reach the population inversion necessary between the Er3+ levels of the transition S-4(3/2) (H-2(11/2)) -> I-4(13/2). An increase of the emission intensity of the sample is observed at the signal wavelength, due to the stimulated emission. Positive optical gain around 2 cm(-1) (8.6 dB/cm) has been measured in Er3+-doped LuVO4 crystal. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000274426800011,
author = {Haro-Gonzalez, P. and Bettinelli, M. and Capuj, N. E. and Lahoz, F. and Martin, I. R. and Cavalli, E. and Gonzalez-Perez, S.},
title = {Optical gain in Er3+-doped transparent LuVO4 crystal at 850 nm},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {32},
number = {3},
pages = {475-478},
doi = {{10.1016/j.optmat.2009.10.012}}
}
|
| Haro-Gonzalez, P., Lahoz, F., Gonzalez-Platas, J., Caceres, J.M., Gonzalez-Perez, S., Marrero-Lopez, D., Capuj, N. & Martin, I.R. ({2008}), "Optical properties of Er3+-doped strontium barium niobate nanocrystals obtained by thermal treatment in glass" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {908-910}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: Measurements of the optical properties of Er3+ ions in strontium barium niobate glass and glass ceramics have been carried out. The glasses have been fabricated using a melt-quenching method, and the glass ceramic samples have been obtained from the glass precursor by a thermal treatment. The ceramic samples formed by a glassy phase, and a crystalline phase contains nanocrystals of Sr1-xBaxNb2O6 (SBN) doped with Er3+ ions with a mean size of similar to 50nm, as confirmed with XRD. Green up-conversion emission has been obtained under excitation at 800 nm, and the temporal evolution of this emission has been reported with the purpose of determining the involved up-conversion mechanism. These optical measures have confirmed that the Er3+ ions have been incorporated into the SBN matrix, after a thermal treatment, which produced an increment of the up-conversion efficiency. (c) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400064,
author = {Haro-Gonzalez, P. and Lahoz, F. and Gonzalez-Platas, J. and Caceres, J. M. and Gonzalez-Perez, S. and Marrero-Lopez, D. and Capuj, N. and Martin, I. R.},
title = {Optical properties of Er3+-doped strontium barium niobate nanocrystals obtained by thermal treatment in glass},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {908-910},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.12.014}}
}
|
| Haro-Gonzalez, P., Lahoz, F., Martin, I.R., Gonzalez-Perez, S. & Capuj, N.E. ({2010}), "OPTICAL GAIN BY UPCONVERSION IN Tm-Yb OXYFLUORIDE GLASS CERAMIC" , In CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS. Vol. {210} , pp. {567-571}. Note:9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008. |
| Abstract: Evidence of positive optical gain is observed in Tm3+-Yb3+ codoped oxyfluoride glass ceramic in an upconversion pump and probe experiment. The (1)G(4) level of the Tm3+ ions is populated by an upconversion mechanism under excitation of the Yb3+ ions at 975 nm with high power pulsed laser and give rise to an intense emission from the (1)G(4) to the F-3(4) levels. The (1)G(4) -> F-3(4) electronic transition is stimulated with a low signal at 650 nm as a probe. Under this condition, we reach the population inversion necessary between the Tm3+ levels of the transition (1)G(4) -> F-3(4) and we observed an increase of the emission intensity at the signal wavelength due to the stimulated emission. Transient positive optical gain around 4 cm(-1) (similar to 17 dB/cm) has been measured in Tm-Yb codoped oxyfluoride glass ceramic. |
BibTeX:
@inproceedings{ISI:000287890200080,
author = {Haro-Gonzalez, P. and Lahoz, F. and Martin, I. R. and Gonzalez-Perez, S. and Capuj, N. E.},
title = {OPTICAL GAIN BY UPCONVERSION IN Tm-Yb OXYFLUORIDE GLASS CERAMIC},
booktitle = {CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS},
year = {2010},
volume = {210},
pages = {567-571},
note = {9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008}
}
|
| Haro-Gonzalez, P., Lahoz, F., Martin, I.R., Gonzalez-Perez, S., Rivera, F. & Capuj, N.E. ({2009}), "Optical amplification in Er3+-doped fluoroindate glass at 840 nm and 1550 nm" , OPTICAL MATERIALS. , JUL, {2009}. Vol. {31} ({9}) , pp. {1370-1372}. Note:2nd International Workshop on Photoluminescence in Rare Earths - Photonic Materials and Devices, Trento, ITALY, MAY 24-25, 2007. |
| Abstract: Er3+-doped transparent fluoroindate glasses have been measured in a pump and probe setup in order to get optical amplification. High power laser pulses at 532 nm have been used as the pump source to strongly populate the S-4(3/2) (H-2(11/2)) levels of Er3+ ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm was used to stimulate the emission associated with the S-4(3/2) (H-2(11/2)) -> I-4(13/2) electronic transition. The high power pump pulses allowed achieving population inversion between the Er3+ levels of the transition S-4(3/2) (H-2(11/2)) -> I-4(13/2). Under these conditions, positive optical gain around 1.33 cm(-1) (5.7 dB/cm) has been measured in Er3+-doped fluoroindate during the first 200 mu s. Using a similar setup experiments of gain have been carried out for the I-4(13/2) -> I-4(15/2) transition of the Er3+ ions (at 1.5 mu m). The obtained values are greater than 1.2 cm(-1) (5.2 dB/cm) during the first 200 mu s. Under these conditions and using the net cross-section simulation, the inversion population of the I-4(13/2 ->) I-4(15/2) transitions could be estimated as 60% in order to obtain optical gain. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000267837200027,
author = {Haro-Gonzalez, P. and Lahoz, F. and Martin, I. R. and Gonzalez-Perez, S. and Rivera, F. and Capuj, N. E.},
title = {Optical amplification in Er3+-doped fluoroindate glass at 840 nm and 1550 nm},
journal = {OPTICAL MATERIALS},
year = {2009},
volume = {31},
number = {9},
pages = {1370-1372},
note = {2nd International Workshop on Photoluminescence in Rare Earths - Photonic Materials and Devices, Trento, ITALY, MAY 24-25, 2007},
doi = {{10.1016/j.optmat.2008.10.014}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Arbelo-Jorge, E., Gonzalez-Perez, S., Caceres, J.M. & Nunez, P. ({2008}), "Laser irradiation in Nd3+ doped strontium barium niobate glass" , JOURNAL OF APPLIED PHYSICS. , JUL 1, {2008}. Vol. {104} ({1}) |
| Abstract: A local nanocrystalline formation in a neodymium doped strontium barium niobate (SBN) glass has been obtained under argon laser irradiation. The intense emission around 880 nm, originated from the F-4(3/2) (F-4(5/2)) thermalized level when the glass structure changes to a glass ceramic structure due to the irradiation of the laser beam, has been studied. The intensities and lifetimes change from this level inside and outside the irradiated area made by the laser excitation. They have been analyzed and demonstrated that the desvitrification process has been successfully achieved. These results confirm that nanocrystals of SBN have been created by the laser action confirming that the transition from glass to glass ceramic has been completed. These results are in agreement with the emission properties of nanocrystals of the bulk glass ceramic sample. The present study also suggests that the SBN nanocrystal has a potential application as temperature detector. (c) 2008 American Institute of Physics. |
BibTeX:
@article{ISI:000257766500013,
author = {Haro-Gonzalez, P. and Martin, I. R. and Arbelo-Jorge, E. and Gonzalez-Perez, S. and Caceres, J. M. and Nunez, P.},
title = {Laser irradiation in Nd3+ doped strontium barium niobate glass},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2008},
volume = {104},
number = {1},
doi = {{10.1063/1.2952011}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Capuj, N.E. & Lahoz, F. ({2010}), "Optical amplification by upconversion in Tm-Yb fluoroindate glass" , OPTICAL MATERIALS. , AUG, {2010}. Vol. {32} ({10}) , pp. {1349-1351}. Note:5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009. |
| Abstract: Evidence of a positive optical gain at 650 nm is observed in Tm3+-Yb3+ codoped fluoroindate glass in an upconversion pump and probe experiment. The (1)G(4) level of the Tm3+ ions is populated by an upconversion mechanism under excitation of the Yb3+ ions at 975 nm with high power pulsed laser and give rise to an intense emission from the (1)G(4) to the F-3(4) levels. The (1)G(4) -> F-3(4) electronic transition is stimulated with a low signal at 650 nm as a probe. Under this condition, we reach the population inversion necessary between the Tm3+ levels of the transition (1)G(4) -> F-3(4) and we observed an increase of the emission intensity at the signal wavelength due to the stimulated emission. Transient positive optical gain around 3 cm(-1) (similar to 12 dB/cm) has been measured in Tm-Yb codoped fluoroindate glass during the first 400 mu s. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000281935100020,
author = {Haro-Gonzalez, P. and Martin, I. R. and Capuj, N. E. and Lahoz, F.},
title = {Optical amplification by upconversion in Tm-Yb fluoroindate glass},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {32},
number = {10},
pages = {1349-1351},
note = {5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009},
doi = {{10.1016/j.optmat.2010.04.013}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Gonzalez-Perez, S., Liu, M., Wang, S.W., Capuj, N. & Lahoz, F. ({2008}), "Increase of the blue upconversion emission in YAG : Tm3+ nanopowders by codoping with Yb3+ ions" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {924-926}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: The YAG nanopowders were prepared by a co-precipitation method using nitrate and ammonium hydrogen carbonate as raw materials. To obtain homogenous precipitate, reverse-strike (adding salt solutions to the precipitant solution) technique was adopted. Therefore, single (Tm3+) and codoped (Tm3+-Yb3+) YAG nanopowders with a size between 40-90 nm have been obtained. Blue upconversion emission at around 480 nm has been found in YAG: Tm3+ nanopowders under excitation to the H-3(4) level of Tm3+ at around 800 nm. However, this upconversion emission in nanopowders codoped with Tm3+-Yb3+ ions is increased by a factor of about 10. The analysis of the temporal evolution of the involved levels and the dependence of the upconversion intensity on the pump power at 800 nm allowed to distinguish the upconversion mechanism. In YAG: Tm3+ nanopowders the upconversion mechanism is due to excited state absorption processes. However, in the codoped samples, Yb3+ ions acts as the sensitizers; in consequence, the blue upconversion is strongly increased. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400069,
author = {Haro-Gonzalez, P. and Martin, I. R. and Gonzalez-Perez, S. and Liu, M. and Wang, S. W. and Capuj, N. and Lahoz, F.},
title = {Increase of the blue upconversion emission in YAG : Tm3+ nanopowders by codoping with Yb3+ ions},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {924-926},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.11.033}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Gonzalez-Perez, S., Martin, L.L., Lahoz, F., Puerto, D. & Solis, J. ({2010}), "FEMTOSECOND LASER MODIFICATION ON STRONTIUM BARIUM NIOBATE GLASSES DOPED WITH Er3+ IONS" , In CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS. Vol. {210} , pp. {573-578}. Note:9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008. |
| Abstract: A localized modification of the optical properties in Er3+ doped Strontium Barium Niobate (SBN) glasses using a femtosecond laser were carried out. The samples were irradiated with a different number of pulses per spot at two laser fluences. Confocal micro-luminescent has been developed to analyze the optical changes produced by exciting the sample with an argon laser. The emission of the Er3+: I-4(11/2) -> I-4(15/2) and I-4(13/2) -> I-4(15/2) transitions are reported and shown structural differences after the femtosecond irradiation. The lifetimes of the levels involved in these transitions are measured inside and outside the damaged area. These measurements are compared with the bulk glass ceramic sample to estimate the optimal condition to produce nanocrystals in a localized area. |
BibTeX:
@inproceedings{ISI:000287890200081,
author = {Haro-Gonzalez, P. and Martin, I. R. and Gonzalez-Perez, S. and Martin, L. L. and Lahoz, F. and Puerto, D. and Solis, J.},
title = {FEMTOSECOND LASER MODIFICATION ON STRONTIUM BARIUM NIOBATE GLASSES DOPED WITH Er3+ IONS},
booktitle = {CERAMIC MATERIALS AND COMPONENTS FOR ENERGY AND ENVIRONMENTAL APPLICATIONS},
year = {2010},
volume = {210},
pages = {573-578},
note = {9th International Symposium on Ceramic Materials for Energy and Environmental Applications/4th Laser Ceramics Symposium, Shanghai, PEOPLES R CHINA, NOV 10-14, 2008}
}
|
| Haro-Gonzalez, P., Martin, I.R., Gonzalez-Perez, S., Martin, L.L., Lahoz, F., Puerto, D. & Solis, J. ({2010}), "Structural changes induced on strontium barium niobate glass by femtosecond laser irradiation" , APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING. , MAR, {2010}. Vol. {98} ({4}) , pp. {879-884}. |
| Abstract: Localized modification of the optical properties of erbium doped strontium barium niobate (SBN) glass has been performed using femtosecond laser irradiation. The samples, with composition SrO-BaO-Nb2O5-B2O5 and doped with 5%mol of Er3+, were fabricated using a melt-quenching method. The samples were irradiated with different number of pulses per spot (1-50 pulses) at two different laser fluences (2.6 and 5.6 J/cm(2)) by using an fs laser amplifier operating at 800 nm and generating pulses with a duration of 120 fs. Micro-luminescent microscopy, using an Ar+ laser as excitation source, has been used to analyze the modifications of the luminescent properties of the sample upon fs laser exposure. The emissions of the Er3+: I-4(11/2)-> I-4(15/2) and I-4(13/2)-> I-4(15/2) transitions allow appreciating the structural modifications caused by femtosecond laser exposure. The lifetimes of the levels involved in these transitions were measured inside and outside the laser irradiated region. These measurements have been compared with those obtained in bulk glass ceramic sample, which is obtained from the glass precursor by a thermal treatment in order to estimate the optimal conditions to produce nanocrystals in a localized region by ultrafast laser irradiation. |
BibTeX:
@article{ISI:000274330700026,
author = {Haro-Gonzalez, P. and Martin, I. R. and Gonzalez-Perez, S. and Martin, L. L. and Lahoz, F. and Puerto, D. and Solis, J.},
title = {Structural changes induced on strontium barium niobate glass by femtosecond laser irradiation},
journal = {APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING},
year = {2010},
volume = {98},
number = {4},
pages = {879-884},
doi = {{10.1007/s00339-009-5468-8}}
}
|
| Haro-Gonzalez, P., Martin, I.R. & Hernandez Creus, A. ({2011}), "Nanocrystals formation on Ho3+ doped strontium barium niobate glass" , JOURNAL OF LUMINESCENCE. , APR, {2011}. Vol. {131} ({4}) , pp. {657-661}. |
| Abstract: The study of two different methods to obtain strontium barium niobate nanocrystals immersed in a glass matrix has been carried out. Ho2O3-doped SrO-BaO-Nb2O5-B2O3 glasses were fabricated using the melt quenching method. Glass ceramic samples were obtained from the precursor glass by thermal treatment in a furnace and by laser irradiation. These glass ceramic samples are formed by a glassy phase and a crystalline phase of strontium barium niobate nanocrystals. This structure was confirmed by X-ray diffraction and Atomic Force Microscope images. The incorporation of Ho3+ ions in the strontium barium niobate nanocrystals were corroborated by optical measurements, which produced an increment in the luminescence intensity compared to the precursor glass. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000289326000020,
author = {Haro-Gonzalez, P. and Martin, I. R. and Hernandez Creus, Alberto},
title = {Nanocrystals formation on Ho3+ doped strontium barium niobate glass},
journal = {JOURNAL OF LUMINESCENCE},
year = {2011},
volume = {131},
number = {4},
pages = {657-661},
doi = {{10.1016/j.jlumin.2010.11.011}}
}
|
| Haro-Gonzalez, P., Martin, I.R. & Hernandez Creus, A. ({2010}), "Nanocrystals distribution inside the writing lines in a glass matrix using Argon laser irradiation" , OPTICS EXPRESS. , JAN 18, {2010}. Vol. {18} ({2}) , pp. {582-590}. |
| Abstract: Localized modification in strontium barium niobate glass doped with Ho3+ under laser irradiation has been carried out. The preliminary samples of this study have been fabricated by the melt quenching method and doped with 2.5% mol of Ho3+. A 3.5W cw multiline Ar-laser has been focused and shifted in a line during laser irradiation. The formation of Strontium Barium Niobate nanocrystals has been confirmed by X-ray diffraction, atomic force microscope image and fluorescence. They have been localized in the irradiation line and change the optical properties of the sample. These nanocrystals have been obtained due to the excitation of the Ho3+ ions which under nonradiative processes produced the heating of the sample. In this work, it has been demonstrated that the diffusion of the Nb5+ ions to the border of the irradiated line controls the growth of the nanocrystals in the sample. (C) 2010 Optical Society of America |
BibTeX:
@article{ISI:000273860400020,
author = {Haro-Gonzalez, P. and Martin, I. R. and Hernandez Creus, Alberto},
title = {Nanocrystals distribution inside the writing lines in a glass matrix using Argon laser irradiation},
journal = {OPTICS EXPRESS},
year = {2010},
volume = {18},
number = {2},
pages = {582-590}
}
|
| Haro-Gonzalez, P., Martin, I.R., Lahoz, F., Gonzalez-Perez, S., Capuj, N.E. & Jaque, D. ({2008}), "Localized desvitrifiation in Er3+-doped strontium barium niobate glass by laser irradiation" , APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING. , DEC, {2008}. Vol. {93} ({4}) , pp. {977-981}. |
| Abstract: Localized desvitrifiation in strontium barium niobate glass doped with Er3+ under laser irradiation has been carried out. The samples of this study have been fabricated by the melt quenching method and doped with 5% mol of Er3+. A 1.5-W cw Ar laser was focused on the sample to obtain desvitrifiation of the glass. Evidence of the changes induced by the Ar laser has been observed through the analysis of the photoluminescence of the Er3+ ions. The transitions corresponding to H-2(11/2)-> I-4(15/2), S-4(3/2)-> I-4(15/2) and F-4(9/2)-> I-4(15/2) have been studied to analyze structure changes. Microluminescence measurements have been carried out to spatially select positions inside and outside the irradiated area. We have observed changes in the emission bands corresponding to these transitions. The emission bands from Er3+ ions in the irradiated zone show a resolved structure while they are broadened outside that area. These changes in the optical properties of the Er3+ ions indicate that the Ar-laser irradiation has produced a change in the local structure of the material. These results show that a localized desvitrifiation has been produced after the laser action and the transition from glass to glass ceramic has been completed. |
BibTeX:
@article{ISI:000260218500027,
author = {Haro-Gonzalez, P. and Martin, I. R. and Lahoz, F. and Gonzalez-Perez, S. and Capuj, N. E. and Jaque, D.},
title = {Localized desvitrifiation in Er3+-doped strontium barium niobate glass by laser irradiation},
journal = {APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING},
year = {2008},
volume = {93},
number = {4},
pages = {977-981},
doi = {{10.1007/s00339-008-4743-4}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Lahoz, F., Gonzalez-Perez, S., Cavalli, E. & Capuj, N.E. ({2009}), "Optical amplification in Er3+-doped transparent Ba2NaNb5O15 single crystal at 850 nm" , JOURNAL OF APPLIED PHYSICS. , DEC 1, {2009}. Vol. {106} ({11}) |
| Abstract: Positive optical gain around 5 cm(-1) (similar to 21 dB/cm) has been observed in Er3+-doped Ba2NaNb5O15 single crystal using a pump and probe experimental setup. High power laser pulses at 532 nm have been used as the pump source in order to strongly populate the S-4(3/2)(H-2(11/2)) levels of the Er3+ ions due to ground state absorption. Low signal beam cw laser radiation at 850 nm has been used as the probe beam to stimulate the emission associated with the S-4(3/2)(H-2(11/2))-> I-4(13/2) electronic transition of the Er3+ ions. The process has been modelized as a four level system, and its population has been analyzed and simulated in order to study the gain dynamics. Optical amplification of the probe signal has been observed during the first 60 mu s, which represents a good agreement between the measured lifetime of the S-4(3/2)(H-2(11/2)) levels and the reported simulation. |
BibTeX:
@article{ISI:000272838600008,
author = {Haro-Gonzalez, P. and Martin, I. R. and Lahoz, F. and Gonzalez-Perez, S. and Cavalli, E. and Capuj, N. E.},
title = {Optical amplification in Er3+-doped transparent Ba2NaNb5O15 single crystal at 850 nm},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2009},
volume = {106},
number = {11},
doi = {{10.1063/1.3267155}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Martin, L.L., Kowalska, D. & Caceres, J.M. ({2010}), "Crystallization effect on Tm3+-Yb3+ codoped SBN glass ceramics" , OPTICAL MATERIALS. , AUG, {2010}. Vol. {32} ({10}) , pp. {1385-1388}. Note:5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009. |
| Abstract: An appropriated thermal treatment of SrO-BaO-Nb2O5-B2O5 glass leads to the formation of glass ceramics which are composed of Tm3+-Yb3+ codoped strontium barium niobate (SBN) nanocrystals dispersed throughout an amorphous matrix. The glasses have been fabricated using a melt-quenching method and after a thermal treatment at 620 degrees C have been obtained the glass ceramic samples. The formation of SBN nanocrystals has been confirmed by the X-ray diffraction patterns. Visible and NIR emission spectra have been reported and confirmed the incorporation of the Tm3+-Yb3+ ions into the SBN nanocrystals. In the glass ceramics samples the decays of Tm3+ levels for the Yb3+-Tm3+ codoped samples are longer than in the Tm3+ single doped samples. This surprising result could be explained in basis to the localisation of the active ions in the SBN nanocrystals. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000281935100030,
author = {Haro-Gonzalez, P. and Martin, I. R. and Martin, L. L. and Kowalska, D. and Caceres, J. M.},
title = {Crystallization effect on Tm3+-Yb3+ codoped SBN glass ceramics},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {32},
number = {10},
pages = {1385-1388},
note = {5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009},
doi = {{10.1016/j.optmat.2010.03.014}}
}
|
| Haro-Gonzalez, P., Martin, I.R., Martin, L.L., Leon-Luis, S.F., Perez-Rodriguez, C., Lavin, V. & MALTA Consolider Team ({2011}), "Characterization of Er3+ and Nd3+ doped Strontium Barium Niobate glass ceramic as temperature sensors" , OPTICAL MATERIALS. , MAR, {2011}. Vol. {33} ({5, Sp. Iss. SI}) , pp. {742-745}. Note:5th Laser Ceramics Symposium - International Symposium on Transparent Ceramics for Photonics Applications, Bilbao, SPAIN, DEC 09-11, 2009. |
| Abstract: Temperature sensor is a vast group of the commercially approachable optical sensors. Recently has appeared a new kind of these devices using the fluorescence intensity ratio (FIR) with a very good sensitivity. The FIR technique has been carried out in Strontium Barium Niobate (SBN) glass ceramic sample to extend the knowledge of this kind of matrix. The samples has been doped with Erbium and Neodymium ions (2.5 mol. The thermalized level S-4(3/2) (H-2(11/2)) of Er3+ ions was studied in a wide temperature range from 300 K to 700 K with a maximum sensitivity of 0.0017 K-1 for 600 K. In these ions the FIR technique has been applied to the transitions H-2(11/2) -> I-4(13/2) and S-4(3/2) -> I-4(13/2) at 800 nm and 850 nm, respectively. The weak overlap between these thermalized emission bands is an important factor to reduce the error in the measurements. In the Nd3+ doped sample, the emission bands corresponding to the F-4(5/2) -> I-4(9/2) and F-4(3/2) -> I-4(9/2) transitions were analyzed as a function of the temperature from 300 K to 700 K with a maximum sensitivity of 0.0015 K-1 for 600 K. These results are compared with other optical devices using FIR technique. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000288578500017,
author = {Haro-Gonzalez, P. and Martin, I. R. and Martin, L. L. and Leon-Luis, Sergio F. and Perez-Rodriguez, C. and Lavin, V. and MALTA Consolider Team},
title = {Characterization of Er3+ and Nd3+ doped Strontium Barium Niobate glass ceramic as temperature sensors},
journal = {OPTICAL MATERIALS},
year = {2011},
volume = {33},
number = {5, Sp. Iss. SI},
pages = {742-745},
note = {5th Laser Ceramics Symposium - International Symposium on Transparent Ceramics for Photonics Applications, Bilbao, SPAIN, DEC 09-11, 2009},
doi = {{10.1016/j.optmat.2010.11.026}}
}
|
| Haro-Gonzalez, P., Martin, L.L., Gonzalez-Perez, S. & Martin, I.R. ({2010}), "Formation of Nd3+ doped Strontium Barium Niobate nanocrystals by two different methods" , OPTICAL MATERIALS. , AUG, {2010}. Vol. {32} ({10}) , pp. {1389-1392}. Note:5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009. |
| Abstract: The study of two different methods to obtain Strontium Barium Niobate nanocrystals has been carried out. Previously, Nd2O3 doped SrO-BaO-Nb2O5-B2O3 glasses were fabricated using the melt quenching process. In the first method, a thermal treatment in an electrical furnace at 620 degrees C was used to obtain glass ceramic samples. In the second one, the nanocrystals were obtained under continuous Ar laser irradiation in a localized zone in the glass sample. The X-ray diffraction patterns confirmed the formation of SBN nanocrystals in both cases. The optical measurements indicate the incorporation of Nd3+ ions into the nanocrystals which produces an increment of the luminescence intensity. Moreover, a calibration with the temperature has been carried out for the ratio of the Nd3+ emissions. This result could let to control the temperature of the laser irradiated zone. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000281935100031,
author = {Haro-Gonzalez, P. and Martin, L. L. and Gonzalez-Perez, S. and Martin, I. R.},
title = {Formation of Nd3+ doped Strontium Barium Niobate nanocrystals by two different methods},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {32},
number = {10},
pages = {1389-1392},
note = {5th International Symposium on Laser, Scintillator and Non Linear Optical Materials (ISLNOM - 5), Pisa, ITALY, SEP 03-05, 2009},
doi = {{10.1016/j.optmat.2010.03.011}}
}
|
| Haro-Gonzalez, P., Martin, L.L., Martin, I.R., Dominiak-Dzik, G.G. & Ryba-Romanowski, W. ({2010}), "Pump and probe measurements of optical amplification at 584 nm in dysprosium doped lithium niobate crystal" , OPTICAL MATERIALS. , DEC, {2010}. Vol. {33} ({2}) , pp. {196-199}. Note:Workshop on International Commission on Glass, Florence, ITALY, APR 28-30, 2010. |
| Abstract: Usually the Dy3+ ions have been used as laser sources associated with the H-6(13/2) -> H-6(15/2) transition about 3 mu m. However, these ions exhibit emissions in the blue (480 nm) and in the yellow (575 nm) that are promising for laser operations. In this work, positive optical gain about 1.9 cm(-1) (similar to 8.2 dB/cm) has been observed at 584 nm in trivalent dysprosium doped lithium niobate crystal, Dy:LiNbO3, using a pump and probe experimental setup. High power laser pulses at 475 nm have been used as the pump source in order to strongly populate the F-4(9/2) level of the Dy3+ ions due to ground state absorption. Low signal beam cw radiation at 584 nm has been used as the probe beam to stimulate the emission associated with the F-4(9/2) -> H-6(13/2) electronic transition of the Dy3+ ions. The process has been modelled as a four level system and the level populations have been analysed and simulated in order to study the gain dynamics. Optical amplification of the probe signal has been observed during the first 300 mu s, which represents a good agreement between the measured lifetime of the F-4(9/2) level and the proposed simulation. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000288284400018,
author = {Haro-Gonzalez, P. and Martin, L. L. and Martin, I. R. and Dominiak-Dzik, G. Grazyna and Ryba-Romanowski, W.},
title = {Pump and probe measurements of optical amplification at 584 nm in dysprosium doped lithium niobate crystal},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {33},
number = {2},
pages = {196-199},
note = {Workshop on International Commission on Glass, Florence, ITALY, APR 28-30, 2010},
doi = {{10.1016/j.optmat.2010.07.017}}
}
|
| Haro-Gonzalez, P., Rivera-Lopez, F., Martin, I.R., Lozano-Gorrin, A.D., Gonzalez-Silgo, C., Sanchez-Fajardo, V.M., Guzman-Afonso, C. & Torres, M.E. ({2010}), "Second harmonic generation in Er3+-Yb3+:YBO3" , MATERIALS LETTERS. , MAR 31, {2010}. Vol. {64} ({6}) , pp. {650-653}. |
| Abstract: Polycrystalline samples of pure and erbium and ytterbium-codoped yttrium borates have been obtained via solid-state reaction and characterized by X-ray diffraction. An appreciable Second Harmonic Generation (SHG) under pulsed excitation at 1064 nm was observed in both compounds matrix. Doping enhances the observed second harmonic generation. which is compatible with a better profile matching refinement in a non-centrosymmetric space group. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000275778300002,
author = {Haro-Gonzalez, P. and Rivera-Lopez, F. and Martin, I. R. and Lozano-Gorrin, A. D. and Gonzalez-Silgo, C. and Sanchez-Fajardo, V. M. and Guzman-Afonso, C. and Torres, M. E.},
title = {Second harmonic generation in Er3+-Yb3+:YBO3},
journal = {MATERIALS LETTERS},
year = {2010},
volume = {64},
number = {6},
pages = {650-653},
doi = {{10.1016/j.matlet.2009.12.016}}
}
|
| Hernandez, S.E., Rodriguez, V.D., Perez, J., Martin, F.A., Castellano, M.A. & Gonzalez-Mora, J.L. ({2009}), "Diffuse reflectance spectroscopy characterization of hemoglobin and intralipid solutions: in vitro measurements with continuous variation of absorption and scattering" , JOURNAL OF BIOMEDICAL OPTICS. , MAY-JUN, {2009}. Vol. {14} ({3}) |
| Abstract: Absorption and scattering processes in biological tissues are studied through reflectance spectroscopy in tissue-like phantoms. For this aim, an experimental setup is designed to independently control both processes in hemoglobin and intralipid solutions. From the analysis of the obtained spectra, a simple empirical power law equation is found that relates absorbance with scattering and absorption coefficients. This relationship includes three wavelength independent parameters, which can be determined geometry from in vitro measurements for each particular optical optode. The dependence of the optical path length on the absorption and scattering coefficients is also analyzed, and estimations of this parameter for physiological conditions are presented. This study is useful to better understand the scattering phenomena in biological tissue, and to obtain absolute concentration of absorber particles when a homogeneous medium can be assumed. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3149864] |
BibTeX:
@article{ISI:000268536300035,
author = {Hernandez, Sergio E. and Rodriguez, Vicente D. and Perez, Justo and Martin, Felipe A. and Castellano, Miguel A. and Gonzalez-Mora, Jose Luis},
title = {Diffuse reflectance spectroscopy characterization of hemoglobin and intralipid solutions: in vitro measurements with continuous variation of absorption and scattering},
journal = {JOURNAL OF BIOMEDICAL OPTICS},
year = {2009},
volume = {14},
number = {3},
doi = {{10.1117/1.3149864}}
}
|
| Hernandez-Cabrera, A. & Aceituno, P. ({2008}), "Calculation of intersubband absorption in doped graded quantum wells under intense terahertz irradiation" , PHYSICAL REVIEW B. , JUL, {2008}. Vol. {78} ({3}) |
| Abstract: In this work, the intersubband absorption is studied in a delta-doped graded quantum well structure with very close excited levels when this structure is subjected to a very intense terahertz irradiation. Multiple peak structure of the absorption is essentially modified by the strong oscillation of deepest excited levels, which periodically changes their energy proximity, and by the appearance of the so-called ``forbidden'' transitions. Effects generated by the oscillatory population of the deepest subbands have been considered. Calculations have been done within the matrix density formalism and the adiabatic approach, taking into account self-consistently electronic levels and depolarization contribution to levels shift. Relaxation rates dependence on terahertz irradiation and charge concentration has been considered. |
BibTeX:
@article{ISI:000258190300078,
author = {Hernandez-Cabrera, A. and Aceituno, P.},
title = {Calculation of intersubband absorption in doped graded quantum wells under intense terahertz irradiation},
journal = {PHYSICAL REVIEW B},
year = {2008},
volume = {78},
number = {3},
doi = {{10.1103/PhysRevB.78.035302}}
}
|
| Hernandez-Cabrera, A., Aceituno, P. & Vasko, F. ({2005}), "Modulation of intersubband infrared absorption under intense terahertz irradiation" , PHYSICAL REVIEW B. , JUL, {2005}. Vol. {72} ({4}) |
| Abstract: We analyze the modification of the intersubband absorption of electrons in quantum wells under intense THz irradiation. An expression for the induced current is obtained, based on the adiabatic approach and the resonant approximation. We predict the occurrence of a significant fine structure as well as the broadening and shift of the absorption under THz pump in a MW cm(-2) intensity range. |
BibTeX:
@article{ISI:000230890300090,
author = {Hernandez-Cabrera, A and Aceituno, P and Vasko, FT},
title = {Modulation of intersubband infrared absorption under intense terahertz irradiation},
journal = {PHYSICAL REVIEW B},
year = {2005},
volume = {72},
number = {4},
doi = {{10.1103/PhysRevB.72.045307}}
}
|
| Hernandez-Cabrera, A., Aceituno, P. & Vasko, F.T. ({2009}), "Negative lateral conductivity of hot electrons in a biased superlattice" , PHYSICAL REVIEW B. , JUN, {2009}. Vol. {79} ({23}) |
| Abstract: Nonequilibrium electron distribution in a superlattice subjected to a homogeneous electric field (biased superlattice with equipopulated levels) is studied within the tight-binding approximation, taking into account the scattering by optical and acoustic phonons and by lateral disorder. It is found that the distribution versus the in-plane kinetic energy depends essentially on the ratio between the Bloch energy, epsilon(B), and the optical phonon energy, (h) over bar omega(0).. The in-plane conductivity is calculated for low-doped structures at temperatures of 4.2 and 20 K. The negative conductivity is found for bias voltages corresponding to epsilon(B)/(h) over bar omega(0) similar or equal to 1/2, 1/3, 2/3,... (the Bloch-phonon resonance condition). |
BibTeX:
@article{ISI:000267699500082,
author = {Hernandez-Cabrera, A. and Aceituno, P. and Vasko, F. T.},
title = {Negative lateral conductivity of hot electrons in a biased superlattice},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {79},
number = {23},
doi = {{10.1103/PhysRevB.79.235312}}
}
|
| Hernandez-Cabrera, A., Aceituno, P. & Vasko, F.T. ({2008}), "Complex permittivity of a biased superlattice" , JOURNAL OF APPLIED PHYSICS. , JAN 1, {2008}. Vol. {103} ({1}) |
| Abstract: We study the intersubband response in a superlattice subjected to a homogeneous electric field (a biased superlattice with equipopulated levels) within the tight-binding approximation. We consider the interplay between homogeneous and inhomogeneous mechanisms of broadening. We calculate the complex dielectric permittivity beyond the Born approximation for a wide spectral region, finding a low-frequency enhancement of the response. A detectable gain below the resonance is obtained for the low-doped GaAs-based biased superlattice in the terahertz spectral region. Conditions of the stimulated emission regime are discussed for metallic and dielectric waveguide structures. It is described that the appearance of a localized terahertz mode is described when a biased superlattice is placed at a vacuum-dielectric interface. (c) 2008 American Institute of Physics. |
BibTeX:
@article{ISI:000252890700088,
author = {Hernandez-Cabrera, A. and Aceituno, P. and Vasko, F. T.},
title = {Complex permittivity of a biased superlattice},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2008},
volume = {103},
number = {1},
doi = {{10.1063/1.2829820}}
}
|
| Hernandez-Cabrera, A., Aceituno, P. & Vasko, F.T. ({2008}), "Quantum wells under an in-plane magnetic field - Effect of the composition parameters on excited electron energy splitting" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {862-864}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: The dependence of the electronic spin-splitting energy on the composition parameters (x,y) in InxGa1-xAs-InyAl1-yAs-based quantum wells, has been calculated. InGaAs narrow gap structures, subjected to in-plane magnetic fields, have been selected because these structures have a big Lande factor. The dependence of the Lande factor both on the applied fields and composition parameters has been included for fixed well width and external electric field. Contributions from the interfaces and strain, which also depend on the composition, are included. Spin-splitting energy and density of states show a strong dependence on the above parameters. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400050,
author = {Hernandez-Cabrera, A. and Aceituno, P. and Vasko, F. T.},
title = {Quantum wells under an in-plane magnetic field - Effect of the composition parameters on excited electron energy splitting},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {862-864},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.11.050}}
}
|
| Hernandez-Cabrera, A., Aceituno, P. & Vasko, F.T. ({2006}), "Electron energy spectrum and density of states for nonsymmetric semiconductor heterostructures in an in-plane magnetic field" , PHYSICAL REVIEW B. , JUL, {2006}. Vol. {74} ({3}) |
| Abstract: Modifications of spin-splitting dispersion relations and density of states for electrons in nonsymmetric heterostructures under in-plane magnetic field are studied within the envelope function formalism. Spin-orbit interactions, caused by both a slow external potential and the heterojunction potentials (which are described by the boundary conditions) are taken into account. The interplay between these contributions and the magnetic field contribution to the spin-splitting term in the Hamiltonian is essential when energy amounts resulting from the Zeeman and spin-orbit coupling are of the same order. Such modifications of the energy spectra allow us to separate the spin-orbit splitting contributions due to a slow external potential and due to the heterojunctions. Numerical estimates for a selectively doped heterojunction and quantum well with a narrow-gap region of electron localization are performed. |
BibTeX:
@article{ISI:000239426700095,
author = {Hernandez-Cabrera, A. and Aceituno, P. and Vasko, F. T.},
title = {Electron energy spectrum and density of states for nonsymmetric semiconductor heterostructures in an in-plane magnetic field},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {74},
number = {3},
doi = {{10.1103/PhysRevB.74.035330}}
}
|
| Hernandez-Concepcion, E., Alonso, D. & Brouard, S. ({2009}), "Entanglement in a continuously measured two-level system coupled to a harmonic oscillator" , PHYSICAL REVIEW A. , MAY, {2009}. Vol. {79} ({5}) |
| Abstract: The dynamics of a two-level system (TLS) coupled to a harmonic oscillator (HO) is studied under the combined effect of a thermal bath acting on the HO and of a detector continuously measuring one of the components of the spinlike TLS. The analysis focuses on the dynamics of the ``relative entropy of entanglement'' (REE) in the one-energy-excitation manifold of the reduced TLS+HO system. For this model system, a stationary state is shown to be reached for which the relative entropy of entanglement is in general nonzero, even though, under certain approximations, the separate effects of bath and detector would be to remove any trace of this resource from the system. Analytical as well as numerical results are obtained for the REE as a function of the different parameters involved in the model definition. |
BibTeX:
@article{ISI:000266500900056,
author = {Hernandez-Concepcion, E. and Alonso, D. and Brouard, S.},
title = {Entanglement in a continuously measured two-level system coupled to a harmonic oscillator},
journal = {PHYSICAL REVIEW A},
year = {2009},
volume = {79},
number = {5},
doi = {{10.1103/PhysRevA.79.052318}}
}
|
| Hernandez-Fernaud, E., Hernandez, B., Ruiz, A., Rodriguez, A. & Betancor, V. ({2008}), "Impact of low-level expression dermatological diseases on the quality of life as a function of its level of specificity" , PSICOTHEMA. , MAY, {2008}. Vol. {20} ({2}) , pp. {273-278}. |
| Abstract: The impact of dermatological diseases on the quality of life is relatively well established, although some results do not support this relationship. Whereas a few studies indicate a decrease in various indicators of quality of life in conditions of disease, in other studies, this,effect has not been observed. These differences can be explained by the use of different concepts of quality of life and / or the comparison of different severity levels of the diseases. The purpose of this paper is to analyze the impact of low-level expression dermatological diseases on various concepts of quality of life. Two hundred-ninety-nine participants completed a questionnaire about symptoms, psychological and psychosocial impact, and general and specific satisfaction. Results show that minor dermatological diseases affect health-related quality of life, but not quality of life considered as well-being. |
BibTeX:
@article{ISI:000255007800016,
author = {Hernandez-Fernaud, Estefania and Hernandez, Bernardo and Ruiz, Antonia and Rodriguez, Armando and Betancor, Veronica},
title = {Impact of low-level expression dermatological diseases on the quality of life as a function of its level of specificity},
journal = {PSICOTHEMA},
year = {2008},
volume = {20},
number = {2},
pages = {273-278}
}
|
| Hernandez-Fernaud, E., Hernandez, B., Ruiz, C. & Ruiz, A. ({2009}), "Development of a Questionnaire to Evaluate Coping Strategies for Skin Problems" , SPANISH JOURNAL OF PSYCHOLOGY. , MAY, {2009}. Vol. {12} ({1}) , pp. {373-382}. |
| Abstract: The aim of this work was to develop an instrument (Coping Strategies for Skin Problems Questionnaire) suitable for identifying the coping strategies people use for general skin problems. We analyzed its psychometric properties when applied to a sample of 299 individuals. Factor analysis shows a 6-factor structure referring to the wish to change. problem-solving strategies. the search for information and asking for social support. the ability, to distance oneself from the problem and to see the positive aspects of the situation. These factors explain 60.77% of the variance and show an internal consistency higher than 0.67. We analyse the validity of the questionnaire and identify different coping profiles depending on the degree of skin damage as assessed by the participants and their search for health services. According to the psychometric properties obtained, we conclude that our instrument is valid and reliable for use with people presenting skin problems. |
BibTeX:
@article{ISI:000265903900035,
author = {Hernandez-Fernaud, Estefania and Hernandez, Bernardo and Ruiz, Cristina and Ruiz, Antonia},
title = {Development of a Questionnaire to Evaluate Coping Strategies for Skin Problems},
journal = {SPANISH JOURNAL OF PSYCHOLOGY},
year = {2009},
volume = {12},
number = {1},
pages = {373-382}
}
|
| Hernandez-Molina, R., Gonzalez-Platas, J., Kovalenko, K.A., Sokolov, M.N., Virovets, A.V., Llusar, R. & Vicent, C. ({2011}), "Cuboidal Mo3S4 and Mo3NiS4 Complexes Bearing Dithiophosphates and Chiral Carboxylate Ligands: Synthesis, Crystal Structure and Fluxionality" , EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. , FEB, {2011}. ({5}) , pp. {683-693}. |
| Abstract: New triangular Mo and W cluster complexes incorporating (S)-lactic acid (HLac), [Mo3S4(mu-Lac)(dtp)(3)(py)] (1) and [W3S4(mu-Lac)(dtp)(3)(py)] (2), were prepared [dtp = (EtO)(2)PS2]. Analogous synthetic procedures were adapted for the synthesis of cuboidal Mo3NiS4 to yield [Mo-3(Nipy)S-4(py)(mu-OAc)( dtp) 3(py)] (3). The crystal structures of 1 and 3 were determined. A detailed variable-temperature P-31H-1 and H-1 NMR study of compounds 1 and 3 indicated fluxional behaviour in non-coordinating solvents (CDCl3, CD2Cl2 and CDCl2CDCl2). A number of dynamic processes were identified involving the Mo-py site that include configuration inversion [(P) to (M)], hindered Mo-N rotation and pyridine exchange. Experiments with deuterated pyridine revealed a faster substitutional lability of Mo-py compared with Ni-py. |
BibTeX:
@article{ISI:000287160800010,
author = {Hernandez-Molina, Rita and Gonzalez-Platas, Javier and Kovalenko, Konstantin A. and Sokolov, Maxim N. and Virovets, Alexandre V. and Llusar, Rosa and Vicent, Cristian},
title = {Cuboidal Mo3S4 and Mo3NiS4 Complexes Bearing Dithiophosphates and Chiral Carboxylate Ligands: Synthesis, Crystal Structure and Fluxionality},
journal = {EUROPEAN JOURNAL OF INORGANIC CHEMISTRY},
year = {2011},
number = {5},
pages = {683-693},
doi = {{10.1002/ejic.201000795}}
}
|
| Hernandez-Molina, R., Kalinina, I., Esparza, P., Sokolov, M., Gonzalez-Platas, J., Estevez-Braun, A. & Perez-Sacau, E. ({2007}), "Complexes of Co(II), Ni(II) and Cu(II) with lapachol" , POLYHEDRON. , OCT 30, {2007}. Vol. {26} ({17}) , pp. {4860-4864}. |
| Abstract: Complexes of naturally occurring hydroxynaphtho-quinone, lapachol (2-hydroxy-3(3-methyl-2-buthenyl)-1,4-naphthoquinone = HL) with Co(II), Ni(II) and Cu(II) have been prepared by reaction of the corresponding acetates with the ligand (HL) in ethanol. The molecular and crystal structures were determined for [CoL2(EtOH)(2)] (1), [NiL2(EtOH)(2)] (2), and [CuL2(py)(2)] (3). In all cases the deprotonated lapachol behaves as chelating bidentate ligand. The complexes were also characterized by elemental analyses, cyclic voltammetry, and FAB-MS. (C) 2007 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000251617600011,
author = {Hernandez-Molina, R. and Kalinina, I. and Esparza, P. and Sokolov, M. and Gonzalez-Platas, J. and Estevez-Braun, A. and Perez-Sacau, E.},
title = {Complexes of Co(II), Ni(II) and Cu(II) with lapachol},
journal = {POLYHEDRON},
year = {2007},
volume = {26},
number = {17},
pages = {4860-4864},
doi = {{10.1016/j.poly.2007.06.022}}
}
|
| Hernandez-Rojas, J., Breton, J., Llorente, J. & Wales, D. ({2005}), "Global minima of (C-60)(n)Ca2+, (C-60)(n)F- and (C-60)(n)I- clusters" , CHEMICAL PHYSICS LETTERS. , JUL 20, {2005}. Vol. {410} ({4-6}) , pp. {404-409}. |
| Abstract: Likely candidates for the lowest potential energy minima of (C-60)(n)Ca2+, (C-60)(n)F- and (C-60)(n)I-, clusters are located using basin-hopping global optimisation. In each case, the potential energy surface is constructed using the Girifalco form for the C60 intermolecular interaction, an averaged Lennard-Jones C-60-ion interaction, and a polarisation potential, which depends on the first few non-vanishing C60 multiPole polarisabilities. We find that the ions generally occupy the interstitial sites of a (C-60)(n) cluster, the coordination shell being tetrahedral for Ca2+ and F-. The F ion has an octahedral coordination shell in the global minimum for (C-60)(6)I-, however for 12 >= n >= 8 the preferred coordination geometry is trigonal prismatic. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000230613900044,
author = {Hernandez-Rojas, J and Breton, J and Llorente, JMG and Wales, DJ},
title = {Global minima of (C-60)(n)Ca2+, (C-60)(n)F- and (C-60)(n)I- clusters},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2005},
volume = {410},
number = {4-6},
pages = {404-409},
doi = {{10.1016/j.cplett.2005.05.075}}
}
|
| Hernandez-Rojas, J., Breton, J., Llorente, J. & Wales, D. ({2004}), "Lowest-energy structures of (C-60)(n)X (X=Li+,Na+,K+,Cl-) and (C-60)(n)YCl (Y=Li,Na,K) clusters for n <= 13" , JOURNAL OF CHEMICAL PHYSICS. , DEC 22, {2004}. Vol. {121} ({24}) , pp. {12315-12322}. |
| Abstract: Basin-hopping global optimization is used to find likely candidates for the lowest minima on the potential energy surface of (C-60)(n)X (X=Li+,Na+,K+,Cl-) and (C-60)(n)YCl (Y=Li,Na,K) clusters with nless than or equal to13. The energy is evaluated using the Girifalco form for the C-60 intermolecular potential along with a polarization potential, which depends on the first few nonvanishing C-60 multipole polarizabilities. We find that the ions occupy interstitial sites of a (C-60)(n) cluster, the coordination shell being triangular for Li+, tetrahedral for Na+ and K+, and octahedral for Cl-. When the required coordination site does not exist in the corresponding (C-60)(n) global minimum, the lowest minimum of the doped system may be based on an alternative geometry. This situation is particularly common in the Cl- complexes, where the (C-60)(n) global minima with icosahedral packing change into decahedral or closed-packed forms for the ions. In all the ions we find a significant binding energy for the doped cluster. In the alkali chloride complexes the preferred coordination for the diatomic moiety is octahedral and is basically determined by the Cl- ion. However, the smaller polarization energies in this case mean that a change in structure from the (C-60)(n) global minimum does not necessarily occur if there is no octahedral site. (C) 2004 American Institute of Physics. |
BibTeX:
@article{ISI:000225714500022,
author = {Hernandez-Rojas, J and Breton, J and Llorente, JMG and Wales, DJ},
title = {Lowest-energy structures of (C-60)(n)X (X=Li+,Na+,K+,Cl-) and (C-60)(n)YCl (Y=Li,Na,K) clusters for n <= 13},
journal = {JOURNAL OF CHEMICAL PHYSICS},
year = {2004},
volume = {121},
number = {24},
pages = {12315-12322},
doi = {{10.1063/1.1819894}}
}
|
| Hernandez-Rojas, J., Calvo, F., Rabilloud, F., Breton, J. & Gomez Llorente, J.M. ({2010}), "Modeling Water Clusters on Cationic Carbonaceous Seeds" , JOURNAL OF PHYSICAL CHEMISTRY A. , JUL 15, {2010}. Vol. {114} ({27}) , pp. {7267-7274}. |
| Abstract: The Dang-Chang many-body polarizable potential has been used to model the interaction between water molecules and a cationic carbonaceous molecule X+, with X = C-60 (buckminsterfullerene), C24H12 (coronene), or C20H10 (corannulene). The most stable structures of (H2O)(n)X+, located with the basin-hopping method, consist of a water cluster next to the carbon cation but often deviate from those obtained for pure water clusters. The accuracy of the intermolecular potential is checked by performing dedicated high-level electronic structure calculations using the B97-1 density functional. Finally, some thermodynamical and dynamical manifestations of the nonwetting behavior are discussed. |
BibTeX:
@article{ISI:000279507600001,
author = {Hernandez-Rojas, J. and Calvo, F. and Rabilloud, F. and Breton, J. and Gomez Llorente, J. M.},
title = {Modeling Water Clusters on Cationic Carbonaceous Seeds},
journal = {JOURNAL OF PHYSICAL CHEMISTRY A},
year = {2010},
volume = {114},
number = {27},
pages = {7267-7274},
doi = {{10.1021/jp101584n}}
}
|
| Hernandez-Rojas, J., Gonzalez, B.S., James, T. & Wales, D.J. ({2006}), "Thermodynamics of water octamer in a uniform electric field" , JOURNAL OF CHEMICAL PHYSICS. , DEC 14, {2006}. Vol. {125} ({22}) |
| Abstract: We study the water octamer in a uniform electric field using the all-exchanges parallel tempering Monte Carlo method in the canonical ensemble. The heat capacity, quenched energy configurations, and the order parameter Q(4) are employed to understand the phase changes observed as a function of temperature and the strength of the applied electric field. At a low field strength of 0.1 V A(-1) a solidlike to liquidlike ``melting'' transition is detected. The corresponding heat capacity peak appears around 206 K, where Q(4) shows a significant change of slope. For E >= 0.5 V A(-1) such features are absent. However, at E=0.5 V A(-1) we find a solidlike to solidlike transition between cubic and extended structures around T similar to 25 K. (c) 2006 American Institute of Physics. |
BibTeX:
@article{ISI:000242855800011,
author = {Hernandez-Rojas, Javier and Gonzalez, Briesta S. and James, Tim and Wales, David J.},
title = {Thermodynamics of water octamer in a uniform electric field},
journal = {JOURNAL OF CHEMICAL PHYSICS},
year = {2006},
volume = {125},
number = {22},
doi = {{10.1063/1.2400853}}
}
|
| Hernandez-Rojas, J. & Llorente, J.M.G. ({2008}), "Microcanonical versus canonical analysis of protein folding" , PHYSICAL REVIEW LETTERS. , JUN 27, {2008}. Vol. {100} ({25}) |
| Abstract: The microcanonical analysis is shown to be a powerful tool to characterize the protein folding transition and to neatly distinguish between good and bad folders. An off-lattice model with parameter chosen to represent polymers of these two types is used to illustrate this approach. Both canonical and microcanonical ensembles are employed. The required calculations were performed using parallel tempering Monte Carlo simulations. The most revealing features of the folding transition are related to its first-order-like character, namely, the S-bend pattern in the caloric curve, which gives rise to negative microcanonical specific heats, and the bimodality of the energy distribution function at the transition temperatures. Models for a good folder are shown to be quite robust against perturbations in the interaction potential parameters. |
BibTeX:
@article{ISI:000257230500070,
author = {Hernandez-Rojas, J. and Llorente, J. M. Gomez},
title = {Microcanonical versus canonical analysis of protein folding},
journal = {PHYSICAL REVIEW LETTERS},
year = {2008},
volume = {100},
number = {25},
doi = {{10.1103/PhysRevLett.100.258104}}
}
|
| Herreros-Cedres, J., Hernandez-Rodriguez, C., Castro, M.P., Montoya, M.M. & Rodriguez, V.L. ({2007}), "Optical anisotropy of TGS(x) center dot TGSe(1-x) compounds" , FERROELECTRICS. Vol. {350} , pp. {22-28}. |
| Abstract: An aqueous solution technique has been used for the growth of TGS(x)center dot TGSe(1-x) mixed crystals. The birefringence and rotation of the optical indicatrix of x selected samples has been measured using the high-accuracy universal polarimeter method. Simple relationships between the spontaneous optical quantities in the ferroelectric phase and the spontaneous polarization are observed. |
BibTeX:
@article{ISI:000247346600003,
author = {Herreros-Cedres, J. and Hernandez-Rodriguez, C. and Castro, M. Pancorbo and Montoya, M. M. and Rodriguez, V. Lopez},
title = {Optical anisotropy of TGS(x) center dot TGSe(1-x) compounds},
journal = {FERROELECTRICS},
year = {2007},
volume = {350},
pages = {22-28},
doi = {{10.1080/00150190701369602}}
}
|
| Herreros-Cedres, J., Hernandez-Rodriguez, C. & Guerrero-Lemus, R. ({2005}), "Optical activity of deuterated analog of L-arginine phosphate single crystals" , In CROSS-DISCIPLINARY APPLIED RESEARCH IN MATERIALS SCIENCE AND TECHNOLOGY. Vol. {480} , pp. {43-51}. Note:1st International Meeting on Applied Physics, Badajoz, SPAIN, OCT 13-18, 2003. |
| Abstract: The complete optical gyration tensor of monoclinic pure L-arginine phosphate monohydrate (LAP) and deuterated LAP (d-LAP) crystals has been determined. Variation of the optical activity in the presence of birefringence of d-LAP crystal with pure LAP is found from the high-accuracy universal polarimeter (HAUP) method at a wavelength of 632.8 nm. The gyration tensor components in terms of rotatory power were found to be p(11) = -6.6(3) degrees/mm, p(22) = 19(2) degrees/mm; p(33) = 49.7(7) degrees/mm; and p(13) = -43.7(8) degrees/mm for the LAP, and p(11) = -1.2(1) degrees/mm, p(22) = 5.0(4) degrees/mm; p(33) = 41.4(3) degrees/mm; and p(13) = -38.0(4) degrees/mm for d-LAP at room temperature. |
BibTeX:
@inproceedings{ISI:000228157300006,
author = {Herreros-Cedres, J and Hernandez-Rodriguez, C and Guerrero-Lemus, R},
title = {Optical activity of deuterated analog of L-arginine phosphate single crystals},
booktitle = {CROSS-DISCIPLINARY APPLIED RESEARCH IN MATERIALS SCIENCE AND TECHNOLOGY},
year = {2005},
volume = {480},
pages = {43-51},
note = {1st International Meeting on Applied Physics, Badajoz, SPAIN, OCT 13-18, 2003}
}
|
| Herreros-Cedres, J., Hernandez-Rodriguez, C. & Guerrero-Lemus, R. ({2006}), "Influence of the imperfect parallelism of crystal faces on high-accuracy universal polarimeter measurements" , JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS. , JAN, {2006}. Vol. {8} ({1}) , pp. {44-48}. |
| Abstract: In the high-accuracy universal polarimeter (HAUP), measurements are performed with plane-parallel plates. The influence of the imperfect parallelism of crystal faces on the determination of the HAUP coefficients is studied. Equations for obtaining the birefringence and optical rotation of the sample are found. Numerical simulations as a function of the wavelength of the light as well as experimental results for a plate of L-arginine phosphate as a function of the temperature are presented. |
BibTeX:
@article{ISI:000236009500007,
author = {Herreros-Cedres, J and Hernandez-Rodriguez, C and Guerrero-Lemus, R},
title = {Influence of the imperfect parallelism of crystal faces on high-accuracy universal polarimeter measurements},
journal = {JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS},
year = {2006},
volume = {8},
number = {1},
pages = {44-48},
doi = {{10.1088/1464-4258/8/1/007}}
}
|
| Herreros-Cedres, J., Hernandez-Rodriguez, C. & Guerrero-Lemus, R. ({2005}), "Comment on `Effect of multiple reflections of light on the optical characteristics of crystals'" , JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS. , MAR, {2005}. Vol. {7} ({3}) , pp. {154-155}. |
| Abstract: A recent paper (Kushnir 2003 J. Opt. A: Pure Appl. Opt. 5 478) describes the effect of multiple reflections of light on the optical characteristics of crystals using a reflection matrix which is generally incorrect. |
BibTeX:
@article{ISI:000228114600010,
author = {Herreros-Cedres, J and Hernandez-Rodriguez, C and Guerrero-Lemus, R},
title = {Comment on `Effect of multiple reflections of light on the optical characteristics of crystals'},
journal = {JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS},
year = {2005},
volume = {7},
number = {3},
pages = {154-155},
doi = {{10.1088/1464-4258/7/3/N01}}
}
|
| Herreros-Cedres, J., Hernandez-Rodriguez, C. & Kaminsky, W. ({2005}), "Absolute optical rotation of CsLiB6O10" , JOURNAL OF APPLIED CRYSTALLOGRAPHY. , JUN, {2005}. Vol. {38} ({Part 3}) , pp. {544-554}. |
| Abstract: The optical rotation ( OR) of CsLiB6O10 (CLBO, space group I (4) over bar 2d) along the a axis has been determined by the HAUP method [Kobayashi & Uesu ( 1983). J Appl. Cryst. 16, 204 - 211] at a wavelength of 632.8 nm and by the TILTER method [Kaminsky & Glazer ( 1996). Ferroelectrics, 183, 133 - 141] at 532 nm and 650 nm. The respective rotatory powers were found to be 17 ( 1), 24 ( 2) and 19 ( 2)degrees mm(-1). The absolute chirality has been established by comparing Bijvoet differences, hkl and k (h) over barl, on the same crystal on which OR was measured. Atomic positions and electron density Fourier peak heights were exploited as input for semi-empirical calculations of refractive indices and OR, using WinOPTACT [ Glazer ( 2002). J. Appl. Cryst. 35, 652] with only one free parameter fitted to match the average refractive index. |
BibTeX:
@article{ISI:000229142100019,
author = {Herreros-Cedres, J and Hernandez-Rodriguez, C and Kaminsky, W},
title = {Absolute optical rotation of CsLiB6O10},
journal = {JOURNAL OF APPLIED CRYSTALLOGRAPHY},
year = {2005},
volume = {38},
number = {Part 3},
pages = {544-554},
doi = {{10.1107/S0021889805009908}}
}
|
| James, T., Wales, D. & Hernandez-Rojas, J. ({2005}), "Global minima for water clusters (H2O)(n), n <= 21, described by a five-site empirical potential" , CHEMICAL PHYSICS LETTERS. , NOV 11, {2005}. Vol. {415} ({4-6}) , pp. {302-307}. |
| Abstract: Candidate global minimum structures are reported for (H2O), clusters for n <= 21 described by the rigid-body TIP5P potential. These structures are compared with previously published results for the related TIP4P potential, and with ab initio calculations at the MP2 level. The variation of the energy gap from the putative global minimum to the next-lowest structure as a function of system size is analysed. Comparisons with previously reported structural trends in water clusters are made. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000233736600024,
author = {James, T and Wales, DJ and Hernandez-Rojas, J},
title = {Global minima for water clusters (H2O)(n), n <= 21, described by a five-site empirical potential},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2005},
volume = {415},
number = {4-6},
pages = {302-307},
doi = {{10.1016/j.cplett.2005.09.019}}
}
|
| Jimenez, C.A., Belmar, J.B., Alderete, J., Delgado, F.S., Lopez-Rodriguez, M., Pena, O., Julve, M. & Ruiz-Perez, C. ({2007}), "New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands" , DALTON TRANSACTIONS. ({21}) , pp. {2135-2144}. |
| Abstract: Four potential tetradentate ligands of formulae 1,2- bis-(3,5-di-tert-butyl-2-hydroxybenzamido)ethane (H4L1, 1), 1,2bis (3,5-di-tert-butyl-2-hydroxybenzamido)propane (H4L2, 2), 1,2-bis-(3,5-di-tert-butyl-2-hydroxybenzamido) benzene (H4L3, 3) and 1,8-bis-(3,5-di-tert-butyl-2-hydroxybenzamido)naphthalene (H4L4, 4) have been prepared and the crystal structures of three of them (1, 3 and 4) determined by single crystal X-ray diffraction. The investigation of their complexing ability toward Co(II) afforded the compounds of formulae [Co-III(L-3)Na-I(H2O)(2)] (5), [Co-III(L-n)Li-I(H2O)(2)] with n = 1 (6), 2 (7) and 3 (8) and [Co-II(L-4)Li-2(I)] (9). Complexes 5-8 are square planar Co-(III) species, as corroborated by the crystal structure of 5. In this compound, two amide-nitrogen and two phenolate-oxygen atoms of a fully deprotonated (L-3)(4-) anion build a slightly distorted square planar surrounding around the cobalt atom, the Co-N distances [1.858(3) and 1.861(3) A] being somewhat longer than the Co-O ones [1.798(3) and 1.801(3) A]. Magnetic and H-1 NMR data at room temperature for 6-8 support the occurrence of an intermediate S = 1 low-lying state for the Co(III) center which is stabilized by the strong donating ability of the fully deprotonated bis- amidate ligands. In the case of the compound with the naphthalene derivative (9), the analytical and spectroscopic data suggest the occurrence of a low spin Co(II) complex. The weakening of the ligand field strength of the tetradentate bis-amidate ligand in the naphthalene derivative (5-6-5 ring-membered fused chelate) when compared to the situation in complexes 5-8 (5-5-5 ring-membered fused chelate) would account for this feature. |
BibTeX:
@article{ISI:000246638100007,
author = {Jimenez, Claudio A. and Belmar, Julio B. and Alderete, Joel and Delgado, Fernando S. and Lopez-Rodriguez, Matias and Pena, Octavio and Julve, Miguel and Ruiz-Perez, Catalina},
title = {New anionic cobalt complexes using highly hindered bis-amides with varying donor abilities as ligands},
journal = {DALTON TRANSACTIONS},
year = {2007},
number = {21},
pages = {2135-2144},
doi = {{10.1039/b617604f}}
}
|
| Jimenez, C.A., Belmar, J.B., Delgado, F.S., Julve, M. & Ruiz-Perez, C. ({2007}), "Structural changes in the crystal packing of highly hindered symmetrical vicinal bis-amides" , CRYSTENGCOMM. Vol. {9} ({9}) , pp. {746-752}. |
| Abstract: The crystal structures of 1,4-bis(3,5-di-tert-butyl-2-hydroxybenzamido)butane ( 1) and 1,3-bis(3,5-di-tert-butyl-2-hydroxybenzamido)-2,2-dimethylpropane ( 2) have being characterized by single crystal X-ray diffraction. Their crystal packing is discussed in terms of the different interactions they exhibit. A brief discussion, based on hydrogen bonds, on the structural features of bis-(3,5-di- tert-butyl-2-hydroxybenzamide) compounds is carried out. |
BibTeX:
@article{ISI:000249078700015,
author = {Jimenez, Claudio A. and Belmar, Julio B. and Delgado, Fernando S. and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Structural changes in the crystal packing of highly hindered symmetrical vicinal bis-amides},
journal = {CRYSTENGCOMM},
year = {2007},
volume = {9},
number = {9},
pages = {746-752},
doi = {{10.1039/b617605d}}
}
|
| Jimenez, C.A., Belmar, J.B., Ortiz, L., Hidalgo, P., Fabelo, O., Pasan, J. & Ruiz-Perez, C. ({2009}), "Influence of the Aliphatic Wrapping in the Crystal Structure of Benzene Tricarboxamide Supramolecular Polymers" , CRYSTAL GROWTH & DESIGN. , DEC, {2009}. Vol. {9} ({12}) , pp. {4987-4989}. |
| Abstract: The syntheses and crystal structures of two novel trisamides, the ethyl-(2) and propyl-substituted (3) N,N',N `'-trialkylbenzene-1,3,5-carboxamides, are reported. The Compounds ire prepared in good yields by aminolysis of the trimethyl-1,3,5-benzenecarboxy late and the respective primary amine. Compound 2 crystallizes in the P2(1)2(1)2(1) space group with a complete molecule in the asymmetric unit and four molecules per unit Cell, whereas 3 does it in the R3c space group with one-third of the molecule in the asymmetric unit and six molecules per unit cell. Their solid-state structures show that the N-H center dot center dot center dot O=C hydrogen bond plays the most important role in the supramolecular framework of both cases, despite considerable differences in crystal packing. Supramolecular sheets are formed in 2, whereas molecules of 3 are packed in a H-bonded primitive cubic [4 6] three-dimensional network. The main difference in the molecular conformation is the tilting of the carboxamide group with respect to the aryl, which in the case of 3 occurs in the same direction, leading to the formation of ``solid-state'' chiral molecules. |
BibTeX:
@article{ISI:000272188000001,
author = {Jimenez, Claudio A. and Belmar, Julio B. and Ortiz, Leandro and Hidalgo, Paulina and Fabelo, Oscar and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Influence of the Aliphatic Wrapping in the Crystal Structure of Benzene Tricarboxamide Supramolecular Polymers},
journal = {CRYSTAL GROWTH & DESIGN},
year = {2009},
volume = {9},
number = {12},
pages = {4987-4989},
doi = {{10.1021/cg801054e}}
}
|
| Kowalska, D., Haro-Gonzalez, P., Martin, I.R. & Caceres, J.M. ({2010}), "Analysis of the optical properties of Er3+-doped strontium barium niobate nanocrystals using time-resolved laser spectroscopy" , APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING. , JUN, {2010}. Vol. {99} ({4}) , pp. {771-776}. |
| Abstract: This paper reports the results obtained in strontium barium niobate (SBN) nanocrystals in glasses doped with 1, 2.5 and 5 mol% of Er3+ ions. The melt-quenching method was applied to fabricate the glasses with composition SrO-BaO-Nb2O5-B2O3 and further thermal treatment was used to obtain glass ceramic samples from the glass precursor. X-ray diffraction patterns confirmed the formation of SBN nanocrystals with an average size of about 50 nm in diameter. Time-resolved fluorescence spectra for the emission of Er3+ ions at 1550 nm have been analyzed in order to confirm the incorporation of the Er3+ ions into the nanocrystals. Green frequency upconversion emission under excitation at 975 nm coming from the ions in the nanocrystals has been obtained. This intense upconversion is about a factor of 500 higher than that obtained from the ions which reside in the glassy phase. Moreover, temporal evolution studies have been carried out with the purpose of determining the involved upconversion mechanism and the importance of these processes as a source of losses for the optical amplification at 1550 nm. |
BibTeX:
@article{ISI:000278519700014,
author = {Kowalska, D. and Haro-Gonzalez, P. and Martin, I. R. and Caceres, J. M.},
title = {Analysis of the optical properties of Er3+-doped strontium barium niobate nanocrystals using time-resolved laser spectroscopy},
journal = {APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING},
year = {2010},
volume = {99},
number = {4},
pages = {771-776},
doi = {{10.1007/s00339-010-5716-y}}
}
|
| Kremer, C., Morales, P., Torres, J., Castiglioni, J., Gonzalez-Platas, J., Hummert, M., Schumann, H. & Dominguez, S. ({2008}), "Novel lanthanide-iminodiacetate frameworks with hexagonal pores" , INORGANIC CHEMISTRY COMMUNICATIONS. , AUG, {2008}. Vol. {11} ({8}) , pp. {862-864}. |
| Abstract: A new family of lanthanide complexes with open-framework structures has been prepared and characterized by X-ray diffraction. The structure of the polymers with general formula [Ln(Hida)(3)] center dot xH(2)O (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb; H(2)ida = iminodiacetic acid) presents large hexagonal channels with more than 11 angstrom diameter, and houses the crystallization water molecules. These molecules can be reversibly removed upon heating. This is the first example of this kind of structure with ida as bridging ligand. (c) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000258215600011,
author = {Kremer, Carlos and Morales, Paula and Torres, Julia and Castiglioni, Jorge and Gonzalez-Platas, Javier and Hummert, Markus and Schumann, Herbert and Dominguez, Sixto},
title = {Novel lanthanide-iminodiacetate frameworks with hexagonal pores},
journal = {INORGANIC CHEMISTRY COMMUNICATIONS},
year = {2008},
volume = {11},
number = {8},
pages = {862-864},
doi = {{10.1016/j.inoche.2008.04.020}}
}
|
| Lacomba-Perales, R., Errandonea, D., Martinez-Garcia, D., Rodriguez-Hernandez, P., Radescu, S., Mujica, A., Munoz, A., Chervin, J.C. & Polian, A. ({2009}), "Phase transitions in wolframite-type CdWO4 at high pressure studied by Raman spectroscopy and density-functional theory" , PHYSICAL REVIEW B. , MAR, {2009}. Vol. {79} ({9}) |
| Abstract: Room-temperature Raman scattering was measured in CdWO4 up to 43 GPa. We report the pressure dependence of all the Raman-active phonons of the low-pressure wolframite phase. As pressure increases changes in the Raman spectra are detected at 20 and 35 GPa due to the onset of reversible structural phase transitions. We also report ab initio total-energy and lattice-dynamics calculations for the different phases of CdWO4. They helped us determine the crystalline structure of the high-pressure phases. Experimental and theoretical results suggest the coexistence of two structures from 20 to 35 GPa: one with tetragonal symmetry and another with triclinic symmetry. Beyond 35 GPa the monoclinic beta fergusonite is proposed as the structure of CdWO4. The pressure evolution of the lattice parameters and the atomic positions of wolframite CdWO4 are also theoretically calculated and an equation of state is reported. |
BibTeX:
@article{ISI:000264768200035,
author = {Lacomba-Perales, R. and Errandonea, D. and Martinez-Garcia, D. and Rodriguez-Hernandez, P. and Radescu, S. and Mujica, A. and Munoz, A. and Chervin, J. C. and Polian, A.},
title = {Phase transitions in wolframite-type CdWO4 at high pressure studied by Raman spectroscopy and density-functional theory},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {79},
number = {9},
doi = {{10.1103/PhysRevB.79.094105}}
}
|
| Lacomba-Perales, R., Martinez-Garcia, D., Errandonea, D., Le Godec, Y., Philippe, J., Le Marchand, G., Chervin, J.C., Polian, A., Munoz, A. & Lopez-Solano, J. ({2010}), "Experimental and theoretical investigation of the stability of the monoclinic BaWO4-II phase at high pressure and high temperature" , PHYSICAL REVIEW B. , APR 1, {2010}. Vol. {81} ({14}) |
| Abstract: In this work we report high-pressure (HP) and high-temperature (HT) ex situ and in situ experiments in BaWO4. Starting from powder samples of BaWO4, scheelite structure (I4(1)/a), we reached conditions of 2.5-5.5 GPa and 400-1100 K using a Paris-Edinburgh press. The quenched samples were characterized by x-ray diffraction and Raman measurements at ambient conditions. Depending upon the final P-T conditions we found either the scheelite or the monoclinic BaWO4-II (P2(1)/n) structure. We also performed HP-HT in situ Raman measurements in a single crystal of BaWO4 using a resistive-heated diamond-anvil cell. The transition from scheelite to the BaWO4-II phase was observed at 5 GPa for T=621 K. Ab initio lattice-dynamics calculations have been performed in order to characterize the vibrations of the BaWO4-II phase. Finally we carried out in situ powder angle-dispersive x-ray diffraction synchrotron measurements on BaWO4 compound following different P-T paths, extending its measured phase diagram in the 2-6 GPa and 300-2000 K range. |
BibTeX:
@article{ISI:000277210200047,
author = {Lacomba-Perales, R. and Martinez-Garcia, D. and Errandonea, D. and Le Godec, Y. and Philippe, J. and Le Marchand, G. and Chervin, J. C. and Polian, A. and Munoz, A. and Lopez-Solano, J.},
title = {Experimental and theoretical investigation of the stability of the monoclinic BaWO4-II phase at high pressure and high temperature},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {14},
doi = {{10.1103/PhysRevB.81.144117}}
}
|
| Lahoz, F. ({2008}), "Ho3+-doped nanophase glass ceramics for efficiency enhancement in silicon solar cells" , OPTICS LETTERS. , DEC 15, {2008}. Vol. {33} ({24}) , pp. {2982-2984}. |
| Abstract: Currently Er3+-doped fluorides are being used as upconversion phosphors to enhance the efficiency of Si solar cells, to our knowledge. However, this enhancement is strongly limited owing to the small solar spectral range around 1540 nm that is used. We demonstrate that Ho3+-doped oxyfluoride glass ceramics are adequate to enlarge the Si sub-bandgap region around 1170 nm that can be transformed into higher-energy photons, showing an upconversion efficiency 2 orders of magnitude higher than the precursor glass. As these materials are transparent at 1540 nm, they can be used complementarily with Er3+-doped phosphors for the same purpose. (C) 2008 Optical Society of America |
BibTeX:
@article{ISI:000262609000034,
author = {Lahoz, Fernando},
title = {Ho3+-doped nanophase glass ceramics for efficiency enhancement in silicon solar cells},
journal = {OPTICS LETTERS},
year = {2008},
volume = {33},
number = {24},
pages = {2982-2984}
}
|
| Lahoz, F., Almenara, J., Rodriguez-Mendoza, U., Martin, I. & Lavin, V. ({2006}), "Dopant partitioning influence on the near-infrared emissions of Tm3+ in oxyfluoride glass ceramics" , JOURNAL OF APPLIED PHYSICS. , MAR 1, {2006}. Vol. {99} ({5}) |
| Abstract: The doping distribution of Tm3+ ions in a transparent oxyfluoride glass ceramic has been investigated. Optical absorption, luminescence, and excitation measurements have been performed in order to determine the environment in which Tm3+ ions and the infrared emissions they give rise to are located. An interesting result has been found: the main contribution to the 1465 nm emission (S band) is due to Tm3+ ions in the crystalline phase for low doping level. However, when the Tm3+ concentration is high the S-band emission comes from the small portion of Tm3+ that remains in the vitreous phase. It has been concluded that cross relaxation (CR) processes are responsible for the quenching of the S-band emission in the crystalline phase for high doping concentration. Lifetime measurements of the H-3(4) level have also been taken and the probability of CR processes deduced. (c) 2006 American Institute of Physics. |
BibTeX:
@article{ISI:000236002900003,
author = {Lahoz, F and Almenara, JM and Rodriguez-Mendoza, UR and Martin, IR and Lavin, V},
title = {Dopant partitioning influence on the near-infrared emissions of Tm3+ in oxyfluoride glass ceramics},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2006},
volume = {99},
number = {5},
doi = {{10.1063/1.2177384}}
}
|
| Lahoz, F., Capuj, N., Haro-Gonzalez, P., Martin, I.R., Perez-Rodriguez, C. & Caceres, J.M. ({2011}), "Stimulated emission in the red, green, and blue in a nanostructured glass ceramics" , JOURNAL OF APPLIED PHYSICS. , FEB 15, {2011}. Vol. {109} ({4}) |
| Abstract: Red, green, and blue stimulated emissions have been achieved in Ho3+ doped oxyfluoride glass ceramic at room temperature. The material shows three emission bands at the red (650 nm), green (545 nm), and blue (488 nm) regions under infrared excitation at 750 nm. These emission bands are caused by a photon avalanche upconversion process previously reported. A pump and probe experimental setup has been designed to show stimulated emissions at the three bands. The pump power threshold for positive gain in the 490 nm band has been estimated around 2.7 kW/cm(2). Higher thresholds are expected for the other bands. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3549157] |
BibTeX:
@article{ISI:000287811100002,
author = {Lahoz, F. and Capuj, N. and Haro-Gonzalez, P. and Martin, I. R. and Perez-Rodriguez, C. and Caceres, J. M.},
title = {Stimulated emission in the red, green, and blue in a nanostructured glass ceramics},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2011},
volume = {109},
number = {4},
doi = {{10.1063/1.3549157}}
}
|
| Lahoz, F., Capuj, N., Oton, C.J. & Cheylan, S. ({2008}), "Optical gain in conjugated polymer hybrid structures based on porous silicon waveguides" , CHEMICAL PHYSICS LETTERS. , OCT 1, {2008}. Vol. {463} ({4-6}) , pp. {387-390}. |
| Abstract: The fabrication and optical characterization of a hybrid waveguide formed by a MDMO-PPV semiconductor layer deposited on a porous silicon cladding is reported. Evidence of amplified spontaneous emission is observed when the intensity of the excitation pump pulses is higher than a certain threshold. A net gain coefficient of about 50 +/- 8 cm(1) is estimated, which is similar to those reported for other PPV derivate conjugated polymers. The demonstration of positive optical gain in these hetero-structures is very promising because new photonic structures could be envisaged due to the versatility of the porous silicon cladding. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000259439200021,
author = {Lahoz, F. and Capuj, N. and Oton, C. J. and Cheylan, S.},
title = {Optical gain in conjugated polymer hybrid structures based on porous silicon waveguides},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2008},
volume = {463},
number = {4-6},
pages = {387-390},
doi = {{10.1016/j.cplett.2008.08.084}}
}
|
| Lahoz, F., Capuj, N.E., Navarro-Urrios, D. & Hernandez, S.E. ({2007}), "Stimulated emission and light amplification in Ho3+ doped oxyfluoride glasses and glass-ceramics - art. no. 65930M" , In Photonic Materials, Devices, and Applications II. Vol. {6593} , pp. {M5930}. Note:Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007. |
| Abstract: Stimulated emission and light amplification have been observed in Ho3+-doped transparent oxyfluoride glasses and glass-ceramics. A Pump and probe experiment has been designed to show this result. A doubled-frequency Nd-YAG pulsed laser oscillating at 532nm was used as the pump source to strongly populate the Ho3+ S-5(2):F-5(4) level. Low power laser radiation at 750nm was used as the probe beam to stimulate the Ho3+ S-5(2):F-5(4) -> I-5(7) electronic transition at the same wavelength. The high power pump pulses provide population inversion between the Ho3+ S-5(2):F-5(4) and I-5(7) electronic levels and a net positive gain in the 750nm signal is observed both in the precursor glass and in the glass-ceramic. The highest optical 2ain was obtained for the glass-ceramic sample and corresponds to about 3.7cm(-1) (similar to 16dB/cm). The dynamics of the gain is also investigated. |
BibTeX:
@inproceedings{ISI:000250171600017,
author = {Lahoz, Fernando and Capuj, Nestor E. and Navarro-Urrios, Daniel and Hernandez, Sergio E.},
title = {Stimulated emission and light amplification in Ho3+ doped oxyfluoride glasses and glass-ceramics - art. no. 65930M},
booktitle = {Photonic Materials, Devices, and Applications II},
year = {2007},
volume = {6593},
pages = {M5930},
note = {Conference on Photonic Materials, Devices and Applications II, Maspalomas, SPAIN, MAY 02-04, 2007},
doi = {{10.1117/12.721884}}
}
|
| Lahoz, F., Haro-Gonzalez, P., Rivera-Lopez, F., Gonzalez-Perez, S., Martin, I.R., Capuj, N.E., Afonso, C.N., Gonzalo, J., Fernandez, J. & Balda, R. ({2008}), "Upconversion emission in Er3+-doped lead niobium germanate thin-film glasses produced by pulsed laser deposition" , APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING. , NOV, {2008}. Vol. {93} ({3}) , pp. {621-625}. |
| Abstract: Thin films of Er3+-doped lead-niobium germanate have been produced by pulsed laser deposition from Er3+-doped 25PbO(2)-25Nb(2)O(5)-50GeO(2) (mol transparent glasses with an Er content in the range 0.5-3 wt The room-temperature infrared to visible upconversion properties of these thin films have been investigated under 800-nm laser excitation. An energy transfer upconversion mechanism has been identified to be responsible for the population of the S-4(3/2):H-2(11/2) excited level, from which an intense green emission occurs. A rate equation analysis supports the proposed mechanism. |
BibTeX:
@article{ISI:000260218400008,
author = {Lahoz, F. and Haro-Gonzalez, P. and Rivera-Lopez, F. and Gonzalez-Perez, S. and Martin, I. R. and Capuj, N. E. and Afonso, C. N. and Gonzalo, J. and Fernandez, J. and Balda, R.},
title = {Upconversion emission in Er3+-doped lead niobium germanate thin-film glasses produced by pulsed laser deposition},
journal = {APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING},
year = {2008},
volume = {93},
number = {3},
pages = {621-625},
doi = {{10.1007/s00339-008-4688-7}}
}
|
| Lahoz, F. & Hassan, M.A. ({2006}), "Upconversion rate in Nd-doped Ta2O5 waveguides and influence on the cw laser performance" , CHEMICAL PHYSICS LETTERS. , JUL 26, {2006}. Vol. {426} ({1-3}) , pp. {135-140}. |
| Abstract: The non-linear upconversion processes in Nd-doped Ta2O5 waveguides have been investigated to determine the depopulation rate of the F-4(3/2) laser level due to energy transfer upconversion (ETU). A rate-equation analysis has been used to obtain analytical expressions of the population and average lifetime of the F-4(3/2) level under modulated cw excitation. The analysis of lifetime measurements as a function of excitation power yielded to an ETU rate of about 22 800 s(-1). Equations for the four level cw laser performance have been obtained using a rate-equation approximation that includes ETU processes. The effect of upconversion on the laser performance has been estimated using the parameters obtained for the Nd-doped Ta2O5 waveguide lasers. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000239272400028,
author = {Lahoz, F. and Hassan, M. A.},
title = {Upconversion rate in Nd-doped Ta2O5 waveguides and influence on the cw laser performance},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2006},
volume = {426},
number = {1-3},
pages = {135-140},
doi = {{10.1016/j.cplett.2006.05.061}}
}
|
| Lahoz, F., Hernandez, S.E., Capuj, N.E. & Navarro-Urrios, D. ({2007}), "Optical amplification in Ho3+-doped transparent oxyfluoride glass ceramics at 750 nm" , APPLIED PHYSICS LETTERS. , MAY 14, {2007}. Vol. {90} ({20}) |
| Abstract: Positive transient optical gain has been demonstrated in Ho3+-doped transparent oxyfluoride glass-ceramics. A pump and probe experiment has been designed to show this result. High power laser pulses at 532 nm were used as the pump source to strongly populate the Ho3+ S-5(2):F-5(4) level due to nonresonant ground state absorption. Low power cw laser radiation at 750 nm was used as the probe beam. The signal beam stimulates the emission associated with the Ho3+ S-5(2):F-5(4)-> I-5(7) electronic transition at 750 nm. In addition to this, the high power pump pulses provide population inversion between the S-5(2):F-5(4) and I-5(7), initial and final states of the transition, respectively, giving rise to the optical amplification of the signal beam. A gain coefficient of 3.7 cm(-1) (similar to 16 dB/cm) was obtained for a pump energy density of about 135 mJ/cm(2) and a signal beam power density of 6 mu W/cm(2). (C) 2007 American Institute of Physics. |
BibTeX:
@article{ISI:000246623500017,
author = {Lahoz, F. and Hernandez, S. E. and Capuj, N. E. and Navarro-Urrios, D.},
title = {Optical amplification in Ho3+-doped transparent oxyfluoride glass ceramics at 750 nm},
journal = {APPLIED PHYSICS LETTERS},
year = {2007},
volume = {90},
number = {20},
doi = {{10.1063/1.2741146}}
}
|
| Lahoz, F., Martin, I. & Alonso, D. ({2005}), "Theoretical analysis of the photon avalanche dynamics in Ho3+-Yb3+ codoped systems under near-infrared excitation" , PHYSICAL REVIEW B. , JAN, {2005}. Vol. {71} ({4}) |
| Abstract: The photon avalanche upconversion mechanism in a Ho3+-Yb3+ system under near infrared excitation is discussed. Two looping cycles in the excitation process provide the necessary population of the I-5(7) intermediate level of Ho3+ ions to achieve the avalanche regime. The first one takes place between Ho3+ ions, while the second one occurs between Ho3+ and Yb3+ ions. We present a simplified model of the process, which only takes into account the ground, intermediate and emitting levels of Ho3+ and the ground and excited levels of Yb3+ ions. The rate equations of the system have been solved, and the photon avalanche regime has been interpreted in terms of gain and loss of the population of the intermediate level. The model predicts a reduction of the avalanche pump power threshold when the Yb3+ concentration increases which is in good agreement with experimental data. |
BibTeX:
@article{ISI:000226736200036,
author = {Lahoz, F and Martin, IR and Alonso, D},
title = {Theoretical analysis of the photon avalanche dynamics in Ho3+-Yb3+ codoped systems under near-infrared excitation},
journal = {PHYSICAL REVIEW B},
year = {2005},
volume = {71},
number = {4},
doi = {{10.1103/PhysRevB.71.045115}}
}
|
| Lahoz, F., Martin, I. & Calvilla-Quintero, J. ({2005}), "Ultraviolet and white photon avalanche upconversion in Ho3+-doped nanophase glass ceramics" , APPLIED PHYSICS LETTERS. , JAN 31, {2005}. Vol. {86} ({5}) |
| Abstract: Ho3+-doped fluoride nanophase glass ceramics have been synthesized from silica-based oxyfluoride glass. An intense white emission light is observed by the naked eye under near infrared excitation at 750 nm. This visible upconversion is due to three strong emission bands in the primary color components, red, green, and blue. Besides, ultraviolet signals are also recorded upon the same excitation wavelength. The excitation mechanism of both the ultraviolet and the visible emissions is a photon avalanche process with a relatively low pump power threshold at about 20 mW. The total upconverted emission intensity has been estimated to increase by about a factor of 20 in the glass ceramic compared to the precursor glass, in which an avalanche type mechanism is not generated. (C) 2005 American Institute of Physics. |
BibTeX:
@article{ISI:000227144700006,
author = {Lahoz, F and Martin, IR and Calvilla-Quintero, JM},
title = {Ultraviolet and white photon avalanche upconversion in Ho3+-doped nanophase glass ceramics},
journal = {APPLIED PHYSICS LETTERS},
year = {2005},
volume = {86},
number = {5},
doi = {{10.1063/1.1861975}}
}
|
| Lahoz, F., Martin, I., Rodriguez-Mendoza, U., Iparraguirre, I., Azkargorta, J., Mendioroz, A., Balda, R., Fernandez, J. & Lavin, V. ({2005}), "Rare earths in nanocrystalline glass-ceramics" , OPTICAL MATERIALS. , OCT, {2005}. Vol. {27} ({11}) , pp. {1762-1770}. Note:2nd International Workshop on Photonic and Electronic Materials, San Sebastian, SPAIN, JUN 14-16, 2004. |
| Abstract: The optical spectroscopic analysis of rare earth ions in transparent oxyfluoride glass-ceramics obtained from SiO2-Al2O3-PbF2-CdF2 based precursor glasses is presented. The oscillator strengths of the optical transitions were measured from the absorption spectra of glasses and glass-ceramics doped with rare earth ions. The results were analysed in the framework of the Judd-Ofelt theory giving the values of the three Omega(2), Omega(4) and Omega(6) intensity parameters over the rare earth series. On the other hand, high efficient infrared-to-blue upconversion has been observed in Tm3+-Yb3+ codoped glass and glass-ceramic compared to the TM3+ single doped matrices. The contributions to the upconversion process of the rare earth ions in the nanocrystalline and in the vitreous phase of the glass-ceramics have been distinguished. Finally, laser action in Nd3+-doped glass-ceramic has been studied. Losses due to UV and visible upconverted emissions inside the laser cavity have been also estimated. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000231965700020,
author = {Lahoz, F and Martin, IR and Rodriguez-Mendoza, UR and Iparraguirre, I and Azkargorta, J and Mendioroz, A and Balda, R and Fernandez, J and Lavin, V},
title = {Rare earths in nanocrystalline glass-ceramics},
journal = {OPTICAL MATERIALS},
year = {2005},
volume = {27},
number = {11},
pages = {1762-1770},
note = {2nd International Workshop on Photonic and Electronic Materials, San Sebastian, SPAIN, JUN 14-16, 2004},
doi = {{10.1016/j.optmat.2004.11.047}}
}
|
| Lahoz, F., Martin, I., Shepherd, D., Wilkinson, J. & Hassan, M. ({2006}), "Room temperature infrared-laser-induced upconversion in Nd3+ doped Ta2O5 waveguides" , CHEMICAL PHYSICS LETTERS. , APR 3, {2006}. Vol. {421} ({1-3}) , pp. {198-204}. |
| Abstract: The room temperature infrared to visible upconversion properties of Nd3+ doped Ta2O5 rib waveguides deposited on a silica substrate have been investigated in the 720-900 nm excitation range. Two possible upconversion mechanisms exist at different excitation wavelengths. The main one is due to energy transfer upconversion and results in the population of the (4)G(7/2) level. Radiative relaxations from this level to the I-4(9/2), I-4(11/2) and I-4(13/2) multiplets produce visible emission bands in the green, orange and red regions. Excited state absorption from the F-4(3/2) to the P-2(1/2) state can also occur, giving rise to a blue emission band (P-2(1/2) -> I-4(9/2)). A rate equation analyses supports the proposed mechanisms. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000236662600040,
author = {Lahoz, F and Martin, IR and Shepherd, DP and Wilkinson, JS and Hassan, MA},
title = {Room temperature infrared-laser-induced upconversion in Nd3+ doped Ta2O5 waveguides},
journal = {CHEMICAL PHYSICS LETTERS},
year = {2006},
volume = {421},
number = {1-3},
pages = {198-204},
doi = {{10.1016/j.cplett.2006.01.076}}
}
|
| Lahoz, F., Oton, C.J., Capuj, N., Ferrer-Gonzalez, M., Cheylan, S. & Navarro-Urrios, D. ({2009}), "Reduction of the amplified spontaneous emission threshold in semiconducting polymer waveguides on porous silica." , OPTICS EXPRESS. , SEP 14, {2009}. Vol. {17} ({19}) , pp. {16766-16775}. |
| Abstract: Hybrid organic-inorganic monomode waveguides of conjugated polymers on porous silicon (PS) substrates have been fabricated. Different low refractive index PS substrates, varying from 1.46 down to 1.18 have been studied. Amplified spontaneous emission (ASE) has been observed for all the samples and the ASE threshold has been monitored as a function of the PS refractive index. A decrease in the ASE threshold is detected when the PS refractive index decreases. These results have been analysed in the frame of a four level waveguide amplifier model and the theoretical predictions are in agreement with the experimental data. (C) 2009 Optical Society of America |
BibTeX:
@article{ISI:000269736100045,
author = {Lahoz, Fernando and Oton, Claudio J. and Capuj, Nestor and Ferrer-Gonzalez, Miriam and Cheylan, Stephanie and Navarro-Urrios, Daniel},
title = {Reduction of the amplified spontaneous emission threshold in semiconducting polymer waveguides on porous silica.},
journal = {OPTICS EXPRESS},
year = {2009},
volume = {17},
number = {19},
pages = {16766-16775}
}
|
| Lahoz, F., Shepherd, D.P., Wilkinson, J.S. & Hassan, M.A. ({2008}), "Efficient blue upconversion emission due to confined radiative energy transfer in Tm3+-Nd3+ co-doped Ta2O5 waveguides under infrared-laser excitation" , OPTICS COMMUNICATIONS. , JUL 15, {2008}. Vol. {281} ({14}) , pp. {3691-3694}. |
| Abstract: Intense blue upconversion emission at 480 nm has been obtained at room temperature in Tm3+-Nd3+ co-doped Ta2O5 channel waveguides fabricated on a Si substrate, when the sample is excited with an infrared laser at 793 nm. The upconversion mechanism is based on the radiative relaxation of the Nd3+ ions (F-4(3/2) -> I-4(11/2)) at about 1064 nm followed by the absorption of the emitted photons by Tm3+ ions in the H-3(4) excited state. A coefficient of energy transfer rate as high as 3 x 10(-16) cm(3)/s has been deduced using a rate equation analysis, which is the highest reported for Tm-Nd co-doped systems. The confinement of the 1064 nm emitted radiation in the waveguide structure is the main reason of the high energy transfer probability between Nd3+ and Tm3+ ions. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000257047700014,
author = {Lahoz, F. and Shepherd, D. P. and Wilkinson, J. S. and Hassan, M. A.},
title = {Efficient blue upconversion emission due to confined radiative energy transfer in Tm3+-Nd3+ co-doped Ta2O5 waveguides under infrared-laser excitation},
journal = {OPTICS COMMUNICATIONS},
year = {2008},
volume = {281},
number = {14},
pages = {3691-3694},
doi = {{10.1016/j.optcom.2008.03.046}}
}
|
| Lang, D.M., Dobson, B., Monzon-Mayor, M., Romero-Aleman, M. d.M., Yanes, C. & Santos, E. ({2007}), "Expression of Nogo-A and Nogo-66 receptor during development and optic nerve regeneration in the lizard, Gallotia galloti" , NEURON GLIA BIOLOGY. Vol. {2} ({Suppl. 1}) , pp. {S118}. |
BibTeX:
@article{ISI:000251708800365,
author = {Lang, Dirk M. and Dobson, Bryony and Monzon-Mayor, Maximina and Romero-Aleman, Maria del Mar and Yanes, Carmen and Santos, Elena},
title = {Expression of Nogo-A and Nogo-66 receptor during development and optic nerve regeneration in the lizard, Gallotia galloti},
journal = {NEURON GLIA BIOLOGY},
year = {2007},
volume = {2},
number = {Suppl. 1},
pages = {S118}
}
|
| Lang, D.M., Monzon-Mayor, M., Romero-Aleman, M. d.M., Yanes, C., Santos, E. & Pesheva, P. ({2008}), "Tenascin-R and axon growth-promoting molecules are up-regulated in the regenerating visual pathway of the lizard (Gallotia galloti)" , DEVELOPMENTAL NEUROBIOLOGY. , JUN, {2008}. Vol. {68} ({7}) , pp. {899-916}. |
| Abstract: It is currently unclear whether retinal ganglion cell (RGC) axon regeneration depends on down-regulation of axon growth-inhibitory proteins, and to what extent outgrowth-promoting substrates contribute to RGC axon regeneration in reptiles. We performed an immunohistochemical study of the regulation of the axon growth-inhibiting extracellular matrix molecules tenascin-R and chondroitin sulphate proteoglycan (CSPG), the axon outgrowth-promoting extracellular matrix proteins fibronectin and laminin, and the axonal tenascin-R receptor protein F3/contactin during RGC axon regeneration in the lizard, Gallotia galloti. Tenascin-R and CSPG were expressed in an extracellular matrix-, oligodendrocyte/myelin- and neuron-associated pattern and up-regulated in the regenerating optic pathway. The expression pattern of tenascin-R was not indicative of a role in channeling or restriction of re-growing RGC axons. Up-regulation of fibronectin, laminin, and F3/contactin occurred in spatiotemporal patterns corresponding to tenascin-R expression. Moreover, we analyzed the influence of substrates containing tenascin-R, fibronectin, and laminin on outgrowth of regenerating lizard RGC axons. In vitro regeneration of RGC axons was not inhibited by tenascin-R, and further improved on mixed substrates containing tenascin-R together with fibronectin or laminin. These results indicate that RGC axon regeneration in Gallotia galloti does not require down-regulation of tenascin-R or CSPG. Presence of tenascin-R is insufficient to prevent RGC axon growth, and concomitant up-regulation of axon growth-promoting molecules like fibronectin and laminin may override the effects of neurite growth inhibitors on RGC axon regeneration. Up-regulation of contactin in RGCs suggests that tenascin-R may have an instructive function during axon regeneration in the lizard optic pathway. (C) 2008 Wiley Periodicals, Inc. |
BibTeX:
@article{ISI:000256611500004,
author = {Lang, Dirk M. and Monzon-Mayor, Maximina and Romero-Aleman, Maria del Mar and Yanes, Carmen and Santos, Elena and Pesheva, Penka},
title = {Tenascin-R and axon growth-promoting molecules are up-regulated in the regenerating visual pathway of the lizard (Gallotia galloti)},
journal = {DEVELOPMENTAL NEUROBIOLOGY},
year = {2008},
volume = {68},
number = {7},
pages = {899-916},
doi = {{10.1002/dneu.20624}}
}
|
| Laporte, G. & Rodriguez Martin, I. ({2007}), "Locating a cycle in a transportation or a telecommunications network" , NETWORKS. , AUG, {2007}. Vol. {50} ({1, Sp. Iss. SI}) , pp. {92-108}. Note:International Network Optimization Conference, Lisbon, PORTUGAL, MAR 20-23, 2005. |
| Abstract: Several problems arising in transportation and telecommunications can be cast in terms of optimally locating a cycle in a graph. This paper proposes a classification of cycle location problems under two main headings. In Hamiltonian problems, all vertices of the graph must belong to the cycle. The most important cases are the traveling salesman problem (TSP), the TSP with precedence constraints, the clustered TSP, the TSP with backhauls, the TSP with time windows, several classes of pickup and delivery problems, and stochastic TSPs. In non-Hamiltonian problems, only a subset of vertices must be visited. These problems include the generalized TSP, the covering tour problem, the median cycle and ring star problems, and several cycle location problems with revenues. These problems are modeled within a unified framework and algorithmic strategies are provided, together with computational results. Several applications are also described. (C) 2007 Wiley Periodicals, Inc. |
BibTeX:
@article{ISI:000248528000011,
author = {Laporte, Gilbert and Rodriguez Martin, Inmaculada},
title = {Locating a cycle in a transportation or a telecommunications network},
journal = {NETWORKS},
year = {2007},
volume = {50},
number = {1, Sp. Iss. SI},
pages = {92-108},
note = {International Network Optimization Conference, Lisbon, PORTUGAL, MAR 20-23, 2005},
doi = {{10.1002/net.20170}}
}
|
| Lavin, V., Lahoz, F., Martin, I., Rodriguez-Mendoza, U. & Caceres, J. ({2005}), "Infrared-to-visible photon avalanche upconversion dynamics in Ho3+-doped fluorozirconate glasses at room temperature" , OPTICAL MATERIALS. , OCT, {2005}. Vol. {27} ({11}) , pp. {1754-1761}. Note:2nd International Workshop on Photonic and Electronic Materials, San Sebastian, SPAIN, JUN 14-16, 2004. |
| Abstract: Blue, green and red emissions have been generated at room temperature by upconversion processes under infrared laser excitation at 750 and 840 nm in fluorozirconate glasses doped with Ho3+ ions. The intense green emission, associated to the S-5(2), F-5(4) -> I-5(8) transitions, has been carefully analysed in order to elucidate the mechanisms involved in the energy conversion process. The temporal dynamics of the emission intensities, the extremely weak ground state absorptions, the strong excited state absorptions and the different cross-relaxation processes indicate that two different photon avalanche mechanisms are responsible of the 750 and 840 nm laser-induced upconversion processes in the Ho3+-doped fluorozirconate glass. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000231965700019,
author = {Lavin, V and Lahoz, F and Martin, IR and Rodriguez-Mendoza, UR and Caceres, JM},
title = {Infrared-to-visible photon avalanche upconversion dynamics in Ho3+-doped fluorozirconate glasses at room temperature},
journal = {OPTICAL MATERIALS},
year = {2005},
volume = {27},
number = {11},
pages = {1754-1761},
note = {2nd International Workshop on Photonic and Electronic Materials, San Sebastian, SPAIN, JUN 14-16, 2004},
doi = {{10.1016/j.optmat.2004.11.046}}
}
|
| Lavin, V., Munoz-Santiuste, J.E., Troester, T., Rodriguez-Mendoza, U.R., Gonzalez-Platas, J., Gonzalez-Silgo, C., Martin, I.R., Rivera-Lopez, F. & Gonzalez-Perez, S. ({2006}), "Pressure- and temperature-induced structural phase transitions in fluoride matrices monitoring by Eu3+ luminescence" , HIGH PRESSURE RESEARCH. , DEC, {2006}. Vol. {26} ({4}) , pp. {411-414}. Note:44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006. |
| Abstract: The precipitation of micro-crystals identified as EuZrF7 has been induced by thermal treatment in the Eu3+-doped fluorozirconate glass. Moreover, using luminiscence of the Eu3+ ion, the experimental evidence of a reverse change has been obtained by a pressure-induced amorphization of the EuZrF7 polycrystal. There is a unique kind of site in the fluorozirconate glass, in which the different environments for the Eu3+ ions are generated by distortions of the EuZrF7 crystalline structure. |
BibTeX:
@article{ISI:000243942800021,
author = {Lavin, V. and Munoz-Santiuste, J. E. and Troester, Th and Rodriguez-Mendoza, U. R. and Gonzalez-Platas, J. and Gonzalez-Silgo, C. and Martin, I. R. and Rivera-Lopez, F. and Gonzalez-Perez, S.},
title = {Pressure- and temperature-induced structural phase transitions in fluoride matrices monitoring by Eu3+ luminescence},
journal = {HIGH PRESSURE RESEARCH},
year = {2006},
volume = {26},
number = {4},
pages = {411-414},
note = {44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006},
doi = {{10.1080/08957950601103932}}
}
|
| Leavens, C.R., Gimenez, I.P., Alonso, D. & Mayato, R.S. ({2006}), "General N-box problem" , PHYSICS LETTERS A. , DEC 4, {2006}. Vol. {359} ({5}) , pp. {416-423}. |
| Abstract: The paradoxical properties of the N-box problem (N >= 3) are dispelled by the straightforward exercise of constructing, for an arbitrary pre-selected state with N nonzero orthogonal components, the corresponding (unique) post-selected state such that this pair leads to the same properties. A new and interesting N-box problem is presented. Crown Copyright (c) 2006 Published by Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000242511200015,
author = {Leavens, C. R. and Gimenez, I. Puerto and Alonso, D. and Mayato, R. Sala},
title = {General N-box problem},
journal = {PHYSICS LETTERS A},
year = {2006},
volume = {359},
number = {5},
pages = {416-423},
doi = {{10.1016/j.physleta.2006.06.089}}
}
|
| Leon-Luis, S.F., Abreu-Afonso, J., Pena-Martinez, J., Mendez-Ramos, J., Yanes, A.C., del Castillo, J. & Rodriguez, V.D. ({2009}), "Up-conversion and colour tuneability in Yb3+-Er3+-Tm3+ co-doped transparent nano-glass-ceramics" , JOURNAL OF ALLOYS AND COMPOUNDS. , JUN 24, {2009}. Vol. {479} ({1-2}) , pp. {557-560}. |
| Abstract: The present work is devoted to the preparation of transparent nano-glass-ceramics (nGC) with composition 30SiO(2)-15AlO(1.5)-29CdF(2)-22PbF(2)-1.5YF(3) co-doped with 1.5YbF(3), 0.5ErF(3) and 0.5TmF(3) (in mol. The co-dopant ions mostly dissolve in the fluoride PbF2-based nano-crystals precipitated during thermal treatment of precursor glasses. Visible up-conversion luminescence, obtained under 980 nm infrared excitation, have been discussed and compared in glasses and daughter nGCs. Specifically, the ratio between red, green and blue up-conversion emissions can be varied with nano-ceramming of the precursor glass resulting in large colour tuneability, which has been quantified in terms of CIE standard chromaticity diagram, with applications in optical integrated devices and tuneable up-conversion phosphors. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000267063300123,
author = {Leon-Luis, S. F. and Abreu-Afonso, J. and Pena-Martinez, J. and Mendez-Ramos, J. and Yanes, A. C. and del-Castillo, J. and Rodriguez, V. D.},
title = {Up-conversion and colour tuneability in Yb3+-Er3+-Tm3+ co-doped transparent nano-glass-ceramics},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2009},
volume = {479},
number = {1-2},
pages = {557-560},
doi = {{10.1016/j.jallcom.2008.12.136}}
}
|
| Lescouezec, R., Toma, L., Vaissermann, J., Verdaguer, M., Delgado, F., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2005}), "Design of single chain magnets through cyanide-bearing six-coordinate complexes" , COORDINATION CHEMISTRY REVIEWS. , DEC 1, {2005}. Vol. {249} ({23}) , pp. {2691-2729}. |
| Abstract: The design and preparation of stable cyanide-bearing six-coordinate complexes of formula [M-III(L)(CN)(x)]((x+t-m)-) = trivalent transition metal ion and L = polydentate blocking ligand are summarized here. Their use as ligands towards either fully hydrated metal ions or coordinatively unsaturated preformed species, to afford a wide variety of low-dimensional metal assemblies whose nuclearity, dimensionality and magnetic properties can be tuned, is also reviewed. Special emphasis is put on the appropriate choice of the end-cap ligand L whose denticity determines the number of coordinated cyanide groups in the mononuclear precursors. Among the different new spin topologies obtained through this rational synthetic strategy, ferromagnetically coupled 4,2-ribbon like bimetallic chains which exhibit slow magnetic relaxation and hysteresis effects (chain as magnets) are one of the most appealing and constitute the heart of the present contribution. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000233814200012,
author = {Lescouezec, R and Toma, LM and Vaissermann, J and Verdaguer, M and Delgado, FS and Ruiz-Perez, C and Lloret, F and Julve, M},
title = {Design of single chain magnets through cyanide-bearing six-coordinate complexes},
journal = {COORDINATION CHEMISTRY REVIEWS},
year = {2005},
volume = {249},
number = {23},
pages = {2691-2729},
doi = {{10.1016/j.ccr.2005.09.017}}
}
|
| Lopez, S., Romero, A.H., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "First-principles study of the high-pressure phase transition in ZnAl2O4 and ZnGa2O4: From cubic spinel to orthorhombic post-spinel structures" , PHYSICAL REVIEW B. , JUN, {2009}. Vol. {79} ({21}) |
| Abstract: In this work we present a first-principles density functional study of the electronic, vibrational, and structural properties of ZnGa2O4 and ZnAl2O4 spinel structures. Here we focus our study in the evolution of the structural properties under hydrostatic pressure. Our results show that ZnGa2O4 under pressure has a first-order phase transition to the marokite (CaMn2O4) structure, which is in good agreement with recent angle-dispersive x-ray diffraction experiments. We also report a similar study for the ZnAl2O4 spinel; we found that this compound under pressure has a first-order phase transition to the orthorhombic CaFe2O4-type structure. Our results in both compounds support, under nonhydrostatic condition, the possibility of a second-order phase transition from the cubic spinel to the tetragonal spinel as reported experimentally in ZnGa2O4. |
BibTeX:
@article{ISI:000267699200033,
author = {Lopez, Sinhue and Romero, A. H. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {First-principles study of the high-pressure phase transition in ZnAl2O4 and ZnGa2O4: From cubic spinel to orthorhombic post-spinel structures},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {79},
number = {21},
doi = {{10.1103/PhysRevB.79.214103}}
}
|
| Lopez-Moreno, S., Rodriguez-Hernandez, P., Munoz, A., Romero, A.H., Manjon, F.J., Errandonea, D., Rusu, E. & Ursaki, V.V. ({2011}), "Lattice dynamics of ZnAl2O4 and ZnGa2O4 under high pressure" , ANNALEN DER PHYSIK. , JAN, {2011}. Vol. {523} ({1-2, Sp. Iss. SI}) , pp. {157-167}. |
| Abstract: In this work we present a first-principles density functional study of the vibrational properties of ZnAl2O4 and ZnGa2O4 as function of hydrostatic pressure. Based on our previous structural characterization of these two compounds under pressure, herewith, we report the pressure dependence on both systems of the vibrational modes for the cubic spinel structure, for the CaFe2O4-type structure (Pnma) in ZnAl2O4 and for marokite (Pbcm) ZnGa2O4. Additionally we report a second order phase transition in ZnGa2O4 from the marokite towards the CaTi2O4-type structure (Cmcm), for which we also calculate the pressure dependence of the vibrational modes at the G point. Our calculations are complemented with Raman scattering measurements up to 12 GPa that show a good overall agreement between our calculated and measured mode frequencies. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim |
BibTeX:
@article{ISI:000285931500013,
author = {Lopez-Moreno, S. and Rodriguez-Hernandez, P. and Munoz, A. and Romero, A. H. and Manjon, F. J. and Errandonea, D. and Rusu, E. and Ursaki, V. V.},
title = {Lattice dynamics of ZnAl2O4 and ZnGa2O4 under high pressure},
journal = {ANNALEN DER PHYSIK},
year = {2011},
volume = {523},
number = {1-2, Sp. Iss. SI},
pages = {157-167},
doi = {{10.1002/andp.201000096}}
}
|
| Lopez-Moreno, S., Romero, A.H., Munoz, A. & Schwingenschloegl, U. ({2010}), "First-principles description of atomic gold chains on Ge(001)" , PHYSICAL REVIEW B. , JAN, {2010}. Vol. {81} ({4}) |
| Abstract: We have performed density-functional theory calculations, including the spin-orbit correction, to investigate atomic gold chains on Ge(001). A set of 26 possible configurations of the Au/Ge(001) system with c(4X2) and c(8X2) symmetries is studied. Our data show that the c(4X2) order results in the lowest energy, which is not in direct agreement with recent experiments. Using total-energy calculations, we are able to explain these differences. We address the electronic band structure and apply the Tersoff-Hamann approach to correlate our data to scanning-tunneling microscopy (STM). We obtain two highly competitive structures of the atomic Au chains for which we report simulated STM images in order to clarify the composition of the experimental Au/Ge(001) surface. |
BibTeX:
@article{ISI:000274002500031,
author = {Lopez-Moreno, S. and Romero, A. H. and Munoz, A. and Schwingenschloegl, U.},
title = {First-principles description of atomic gold chains on Ge(001)},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {4},
doi = {{10.1103/PhysRevB.81.041415}}
}
|
| Lopez-Moreno, S., Romero, A.H., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "Ab initio study of the high-pressure phases and dynamical properties of ZnAl2O4 and ZnGa2O4" , HIGH PRESSURE RESEARCH. Vol. {29} ({4}) , pp. {573-577}. Note:47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009. |
| Abstract: In this paper, we report ab initio calculations of the vibrational and structural properties of ZnAl2O4 and ZnGa2O4 spinel structures. The calculated vibrational modes at zero pressure, at the point and the complete phonon spectrum of both compounds are presented. Also, we report our findings for the high-pressure structure dependences of spinel and post-spinel structures. |
BibTeX:
@article{ISI:000274675700021,
author = {Lopez-Moreno, S. and Romero, A. H. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Ab initio study of the high-pressure phases and dynamical properties of ZnAl2O4 and ZnGa2O4},
journal = {HIGH PRESSURE RESEARCH},
year = {2009},
volume = {29},
number = {4},
pages = {573-577},
note = {47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009},
doi = {{10.1080/08957950903474635}}
}
|
| Lopez-Moreno, S., Romero, A.H., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "Ab initio calculations of the wolframite MnWO4 under high pressure" , HIGH PRESSURE RESEARCH. Vol. {29} ({4}) , pp. {578-581}. Note:47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009. |
| Abstract: Ab initio calculations, based on the density functional theory, of the structural properties of MnWO4 wolframite compound are reported. We obtain the equilibrium volume from an equation of state with the anti-ferromagnetic (AF) and ferromagnetic configurations, AF being the lowest energy state, and the structural properties of the wolframite structure at zero pressure are obtained. We also study the wolframite structure up to a pressure of 31GPa, and the pressure evolution of structural parameters is found to be in good agreement with the available experimental data. |
BibTeX:
@article{ISI:000274675700022,
author = {Lopez-Moreno, S. and Romero, A. H. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Ab initio calculations of the wolframite MnWO4 under high pressure},
journal = {HIGH PRESSURE RESEARCH},
year = {2009},
volume = {29},
number = {4},
pages = {578-581},
note = {47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009},
doi = {{10.1080/08957950903438481}}
}
|
| Lopez-Solano, J., Munoz, A. & Mujica, A. ({2007}), "Structural phases of InAs under pressure" , PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS. , JAN, {2007}. Vol. {244} ({1}) , pp. {274-278}. Note:12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006. |
| Abstract: We present the results of a theoretical study on the structural stability of InAs under high pressure, with a focus on the pressure regime past the first transition from the low-pressure zincblende phase to the rock-salt (NaCl-type) phase. We have examined several candidates proposed for low-enthalpy phases at higher pressures, among them the super-Cmcm structure observed in InSb at moderately high pressure and the B10 structure, which is a distortion of the CsCl structure. Our results reproduce the established sequence of transitions and shed further light on the higher pressure regime of this material. |
BibTeX:
@article{ISI:000243693600049,
author = {Lopez-Solano, J. and Munoz, A. and Mujica, A.},
title = {Structural phases of InAs under pressure},
journal = {PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS},
year = {2007},
volume = {244},
number = {1},
pages = {274-278},
note = {12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006},
doi = {{10.1002/pssb.200672560}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "Ab initio study of high-pressure structural properties of the LuVO4 and ScVO4 zircon-type orthovanadates" , HIGH PRESSURE RESEARCH. Vol. {29} ({4}) , pp. {582-586}. Note:47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009. |
| Abstract: We use ab initio theoretical methods to study the relative stability under pressure of the zircon, scheelite and fergusonite structures in the LuVO4 and ScVO4 orthovanadates. In LuVO4, our study confirms the zirconscheelitefergusonite sequence of stable phases proposed in previous experimental works. In ScVO4, we find a zircon-to-scheelite phase transition in agreement with experiments. At higher pressures, our calculations show that the scheelite phase becomes unstable with respect to the fergusonite phase, although no second phase transition has been observed in experiments. |
BibTeX:
@article{ISI:000274675700023,
author = {Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Ab initio study of high-pressure structural properties of the LuVO4 and ScVO4 zircon-type orthovanadates},
journal = {HIGH PRESSURE RESEARCH},
year = {2009},
volume = {29},
number = {4},
pages = {582-586},
note = {47th Meeting of the European-High-Pressure-Research-Group (EHPRG 47), Paris, FRANCE, SEP 06-11, 2009},
doi = {{10.1080/08957950903417444}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P., Munoz, A., Gomis, O., Santamaria-Perez, D., Errandonea, D., Manjon, F.J., Kumar, R.S., Stavrou, E. & Raptis, C. ({2010}), "Theoretical and experimental study of the structural stability of TbPO4 at high pressures" , PHYSICAL REVIEW B. , APR 1, {2010}. Vol. {81} ({14}) |
| Abstract: We have performed a theoretical and experimental study of the structural stability of terbium phosphate at high pressures. Theoretical ab initio total-energy and lattice-dynamics calculations together with x-ray diffraction experiments have allowed us to completely characterize a phase transition at similar to 9.8 GPa from the zircon to the monazite structure. Furthermore, total-energy calculations have been performed to check the relative stability of 17 candidate structures at different pressures and allow us to propose the zircon -> monazite -> scheelite -> SrUO4-type sequence of stable structures with increasing pressure. In this sequence, sixfold P coordination is attained for the SrUO4-type structure above 64 GPa. The whole sequence of transitions is discussed in association with the high-pressure structural behavior of oxides isomorphic to TbPO4. |
BibTeX:
@article{ISI:000277210200056,
author = {Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A. and Gomis, O. and Santamaria-Perez, D. and Errandonea, D. and Manjon, F. J. and Kumar, R. S. and Stavrou, E. and Raptis, C.},
title = {Theoretical and experimental study of the structural stability of TbPO4 at high pressures},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {14},
doi = {{10.1103/PhysRevB.81.144126}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P., Munoz, A. & Manjon, F. ({2006}), "Theoretical study of the YLiF4 phase transitions under pressure" , PHYSICAL REVIEW B. , MAR, {2006}. Vol. {73} ({9}) |
| Abstract: Experimental work has shown that YLiF4 has a first phase transition from the ambient pressure scheelite to a fergusonite structure at 10 GPa, and a second one at 17 GPa to an unresolved structure. Theoretical work has proposed either M- or M-'-fergusonite as the second structural phase, and wolframite or a P2(1)/c-symmetry structure as the third. In this ab initio study, we find that the M-'-fergusonite structure is a better candidate for the second phase of YLiF4, and propose a new structure with Cmca symmetry as the third. |
BibTeX:
@article{ISI:000236467100063,
author = {Lopez-Solano, J and Rodriguez-Hernandez, P and Munoz, A and Manjon, FJ},
title = {Theoretical study of the YLiF4 phase transitions under pressure},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {73},
number = {9},
doi = {{10.1103/PhysRevB.73.094117}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P., Munoz, A. & Manjon, F.J. ({2006}), "Theoretical study of the scheelite-to-fergusonite phase transition in YLiF4 under pressure" , JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS. , SEP-OCT, {2006}. Vol. {67} ({9-10, Sp. Iss. SI}) , pp. {2077-2082}. Note:Conference on Study of Matter at Extreme Conditions (SMEC2005), Miami Beach, FL, APR 17-21, 2005. |
| Abstract: Recent experimental works on high-pressure X-ray diffraction have shown that YLiF4 undergoes a reversible phase transition around 10 GPa from the ambient pressure scheelite-type to a fergusonite-type structure. Different theoretical works have proposed either the M-fergusonite or M'-fergusonite as this second stable structure. Also, small changes in photoluminescence and Raman signals have been observed around 6GPa, and have not been completely explained yet. In this work we present a first-principles Density Functional Theory structural study of YLiF4. We found that the anomalies at 6 GPa can be related to the structural changes observed in a scheelite to M'-fergusonite transition. We also have studied briefly different possibilities for an experimentally observed but not completly characterised third stable structure above 17 GPa. (c) 2006 Published by Elsevier Ltd. |
BibTeX:
@article{ISI:000241089600025,
author = {Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A. and Manjon, F. J.},
title = {Theoretical study of the scheelite-to-fergusonite phase transition in YLiF4 under pressure},
journal = {JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS},
year = {2006},
volume = {67},
number = {9-10, Sp. Iss. SI},
pages = {2077-2082},
note = {Conference on Study of Matter at Extreme Conditions (SMEC2005), Miami Beach, FL, APR 17-21, 2005},
doi = {{10.1016/j.jpcs.2006.05.026}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P., Munoz, A., Santamaria-Perez, D., Manjon, F.J., Ray, S., Gomis, O., Mollar, M., Panchal, V. & Errandonea, D. ({2011}), "High-pressure theoretical and experimental study of HgWO4" , HIGH PRESSURE RESEARCH. Vol. {31} ({1}) , pp. {58-63}. |
| Abstract: HgWO4 at ambient pressure is characterized using a combination of ab initio calculations, X-ray diffraction and Raman scattering measurements. The effect of low pressure and temperature on the structural stability is analysed. Extending our ab initio study to the range of higher pressures, a sequence of stable phases up to 30GPa is proposed. |
BibTeX:
@article{ISI:000288660500013,
author = {Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A. and Santamaria-Perez, D. and Manjon, F. J. and Ray, S. and Gomis, O. and Mollar, M. and Panchal, V. and Errandonea, D.},
title = {High-pressure theoretical and experimental study of HgWO4},
journal = {HIGH PRESSURE RESEARCH},
year = {2011},
volume = {31},
number = {1},
pages = {58-63},
doi = {{10.1080/08957959.2010.521735}}
}
|
| Lopez-Solano, J., Rodriguez-Hernandez, P., Radescu, S., Mujica, A., Munoz, A., Errandonea, D., Manjon, F.J., Pellicer-Porres, J., Garro, N., Segura, A., Ferrer-Roca, C., Kumar, R.S., Tschauner, O. & Aquilanti, G. ({2007}), "Crystal stability and pressure-induced phase transitions in scheelite AWO(4) (A = Ca, Sr, Ba, Pb, Eu) binary oxides. I: A review of recent ab initio calculations, ADXRD, XANES, and Raman studies" , PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS. , JAN, {2007}. Vol. {244} ({1}) , pp. {325-330}. Note:12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006. |
| Abstract: The structural properties of CaWO4, SrWO4, BaWO4, PbWO4, and EuWO4 scintillating crystals under pressure have been studied by X-ray powder diffraction, X-ray absorption near-edge structure measurements, Raman spectroscopy, and ab initio density functional theory calculations. The results obtained from these studies will be reviewed here and their differences and similitudes discussed. |
BibTeX:
@article{ISI:000243693600058,
author = {Lopez-Solano, J. and Rodriguez-Hernandez, P. and Radescu, S. and Mujica, A. and Munoz, A. and Errandonea, D. and Manjon, F. J. and Pellicer-Porres, J. and Garro, N. and Segura, A. and Ferrer-Roca, Ch. and Kumar, R. S. and Tschauner, O. and Aquilanti, G.},
title = {Crystal stability and pressure-induced phase transitions in scheelite AWO(4) (A = Ca, Sr, Ba, Pb, Eu) binary oxides. I: A review of recent ab initio calculations, ADXRD, XANES, and Raman studies},
journal = {PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS},
year = {2007},
volume = {244},
number = {1},
pages = {325-330},
note = {12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006},
doi = {{10.1002/pssb.200672559}}
}
|
| Machon, D., Toulemonde, P., McMillan, P.F., Amboage, M., Munoz, A., Rodriguez-Hernandez, P. & San Miguel, A. ({2009}), "High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrate Rb6.15Si46" , PHYSICAL REVIEW B. , MAY, {2009}. Vol. {79} ({18}) |
| Abstract: The type-I clathrate Rb6.15Si46 with partly empty cage sites has been studied up to 36 GPa using Raman spectroscopy, synchrotron x-ray diffraction in diamond-anvil cells, and ab initio total-energy and lattice-dynamics calculations. A first phase transition is observed at 13 +/- 1 GPa and a ``volume collapse'' transition within the clathrate structure is then observed at 24 +/- 1 GPa. Pressure-induced amorphization into a high-density amorphous (HDA) state occurs above P=33 +/- 1 GPa. The HDA form transforms into a low-density amorphous polymorph during decompression. During the compression study using angle dispersive synchrotron x-ray diffraction techniques we measured bulk modulus parameters for rocksalt-structured TaO, included adventitiously in the clathrate sample [K-0=293(3) GPa and K-0(')=5.4(3)]. |
BibTeX:
@article{ISI:000266501200030,
author = {Machon, D. and Toulemonde, P. and McMillan, P. F. and Amboage, M. and Munoz, A. and Rodriguez-Hernandez, P. and San Miguel, A.},
title = {High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrate Rb6.15Si46},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {79},
number = {18},
doi = {{10.1103/PhysRevB.79.184101}}
}
|
| Madalan, A., Ruiz-Perez, C., Melnic, E., Kravtsovc, V. & Andruh, M. ({2005}), "Mononuclear and one-dimensional polynuclear Cu(II) complexes with two different chelatic ligands. Syntheses, structural and spectral characterization of [Cu(acac)(phen)(H2O)](ClO4) [Cu(acac)(bipym)(ClO4](n)" , REVUE ROUMAINE DE CHIMIE. , JAN, {2005}. Vol. {50} ({1}) , pp. {11-17}. |
| Abstract: Two new complexes containing the acetylacetonato ligand have been obtained and cryslallographically characterized, [Cu(acac)(phen)(H2O)](ClO4) - 1 and [Cu(acac)(bipym)(ClO4)](n) - 2 (acac = acetylacetonate, phen = 1,10-phenantroline, bipym = 2,2'-bipyrimidine). In 1 the copper(II) ion exhibits a square pyramidal geometry with the chelatic ligands forming the basal plane, and the water molecule coordinated in the apical position. The O-H...O hydrogen bonds and pi-pi stacking interactions unite complexes in supramolecular layers. In the polynuclear complex 2, the copper(II) ions are placed in a distorted octahedral environment with the chelatic ligands in the equatorial plane and weakly connected perclorate anions in the axial positions, acting as bridges resulting in infinite polynuclear chain. The spectral properties of the two compounds were investigated in the UV, visible and IR domains. |
BibTeX:
@article{ISI:000237530100002,
author = {Madalan, AM and Ruiz-Perez, C and Melnic, E and Kravtsovc, V and Andruh, M},
title = {Mononuclear and one-dimensional polynuclear Cu(II) complexes with two different chelatic ligands. Syntheses, structural and spectral characterization of [Cu(acac)(phen)(H2O)](ClO4) [Cu(acac)(bipym)(ClO4](n)},
journal = {REVUE ROUMAINE DE CHIMIE},
year = {2005},
volume = {50},
number = {1},
pages = {11-17}
}
|
| Manjon, F.J., Errandonea, D., Garro, N., Pellicer-Porres, J., Lopez-Solano, J., Rodriguez-Hernandez, P., Radescu, S., Mujica, A. & Munoz, A. ({2006}), "Lattice dynamics study of scheelite tungstates under high pressure II. PbWO4" , PHYSICAL REVIEW B. , OCT, {2006}. Vol. {74} ({14}) |
| Abstract: Room-temperature Raman scattering has been measured in lead tungstate up to 17 GPa. We report the pressure dependence of all the Raman modes of the tetragonal scheelite phase (PbWO4-I or stolzite, space group I4(1)/a), which is stable at ambient conditions. Upon compression the Raman spectrum undergoes significant changes around 6.2 GPa due to the onset of a partial structural phase transition to the monoclinic PbWO4-III phase (space group P2(1)/n). Further changes in the spectrum occur at 7.9 GPa, related to a scheelite-to-fergusonite transition. This transition is observed due to the sluggishness and kinetic hindrance of the I -> III transition. Consequently, we found the coexistence of the scheelite, PbWO4-III, and fergusonite phases from 7.9 to 9 GPa, and of the last two phases up to 14.6 GPa. We have performed ab initio lattice-dynamics calculations, which have greatly helped us in assigning the Raman modes of the three phases and discussing their pressure dependence. The Raman modes of the free WO4 molecule are discussed. |
BibTeX:
@article{ISI:000241723400032,
author = {Manjon, F. J. and Errandonea, D. and Garro, N. and Pellicer-Porres, J. and Lopez-Solano, J. and Rodriguez-Hernandez, P. and Radescu, S. and Mujica, A. and Munoz, A.},
title = {Lattice dynamics study of scheelite tungstates under high pressure II. PbWO4},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {74},
number = {14},
doi = {{10.1103/PhysRevB.74.144112}}
}
|
| Manjon, F.J., Errandonea, D., Garro, N., Pellicer-Porres, J., Rodriguez-Hernandez, P., Radescu, S., Lopez-Solano, J., Mujica, A. & Munoz, A. ({2006}), "Lattice dynamics study of scheelite tungstates under high pressure I. BaWO4" , PHYSICAL REVIEW B. , OCT, {2006}. Vol. {74} ({14}) |
| Abstract: Room-temperature Raman scattering has been measured in barium tungstate (BaWO4) up to 16 GPa. We report the pressure dependence of all the Raman active first-order phonons of the tetragonal scheelite phase (BaWO4-I, space group I4(1)/a), which is stable at normal conditions. As pressure increases the Raman spectrum undergoes significant changes around 6.9 GPa due to the onset of the structural phase transition to the monoclinic BaWO4-II phase (space group P2(1)/n). This transition is only completed above 9.5 GPa. A further change in the spectrum is observed at 7.5 GPa related to a scheelite-to-fergusonite transition. The scheelite, BaWO4-II, and fergusonite phases coexist up to 9.0 GPa due to the sluggishness of the I -> II phase transition. Further to the experimental study, we have performed ab initio lattice dynamics calculations that have greatly helped us in assigning and discussing the pressure behavior of the observed Raman modes of the three phases. |
BibTeX:
@article{ISI:000241723400031,
author = {Manjon, F. J. and Errandonea, D. and Garro, N. and Pellicer-Porres, J. and Rodriguez-Hernandez, P. and Radescu, S. and Lopez-Solano, J. and Mujica, A. and Munoz, A.},
title = {Lattice dynamics study of scheelite tungstates under high pressure I. BaWO4},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {74},
number = {14},
doi = {{10.1103/PhysRevB.74.144111}}
}
|
| Manjon, F.J., Errandonea, D., Lopez-Solano, J., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "Negative pressures in CaWO4 nanocrystals" , JOURNAL OF APPLIED PHYSICS. , MAY 1, {2009}. Vol. {105} ({9}) |
| Abstract: Tetragonal scheelite-type CaWO4 nanocrystals recently prepared by a hydrothermal method show an enhancement of its structural symmetry with the decrease in nanocrystal size. The analysis of the volume dependence of the structural parameters in CaWO4 nanocrystals with the help of ab initio total-energy calculations shows that the enhancement of the symmetry in the scheelite-type nanocrystals is a consequence of the negative pressure exerted on the nanocrystals; i.e., the nanocrystals are under tension. Besides, the behavior of the structural parameters in CaWO4 nanocrystals for sizes below 10 nm suggests an onset of a scheelite-to-zircon phase transformation in good agreement with the predictions from our ab initio calculations. CaWO4 nanocrystals exhibit a reconstructive-type mechanism for the scheelite-to-zircon phase transition that seems to follow the tetragonal path that links both structures. This result is in contrast with the mechanism recently proposed for this transition in bulk ZrSiO4 where the transition goes through an intermediate monoclinic phase. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3116727] |
BibTeX:
@article{ISI:000266263300152,
author = {Manjon, F. J. and Errandonea, D. and Lopez-Solano, J. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Negative pressures in CaWO4 nanocrystals},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2009},
volume = {105},
number = {9},
doi = {{10.1063/1.3116727}}
}
|
| Manjon, F.J., Errandonea, D., Lopez-Solano, J., Rodriguez-Hernandez, P., Radescu, S., Mujica, A., Munoz, A., Garro, N., Pellicer-Porres, J., Segura, A., Ferrer-Roca, C., Kumar, R.S., Tschauner, O. & Aquilantfi, G. ({2007}), "Crystal stability and pressure-induced phase transitions in scheelite AWO(4) (A = Ca, Sr, Ba, Pb, Eu) binary oxides. II: Towards a systematic understanding" , PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS. , JAN, {2007}. Vol. {244} ({1}) , pp. {295-302}. Note:12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006. |
| Abstract: Recent experimental measurements and ab initio calculations in scheelite CaWO4, SrWO4, BaWO4, PbWO4, EuWO4 and YLiF4 crystals reveal the existence of complex high-pressure phase diagrams, which present striking differences but also relevant similarities. In this work we show that the high-pressure structural sequence in the studied scheelites can be understood on the basis of the positions of the different ABX(4) compounds in Fukunaga and Yamaoka's diagram and in Bastide's diagram. Our study can help to understand the phase diagrams and high-pressure phase transitions occurring in ABX(4) compounds with scheelite, wolframite, fergusonite, zircon, or pseudoscheelite structures. |
BibTeX:
@article{ISI:000243693600053,
author = {Manjon, F. J. and Errandonea, D. and Lopez-Solano, J. and Rodriguez-Hernandez, P. and Radescu, S. and Mujica, A. and Munoz, A. and Garro, N. and Pellicer-Porres, J. and Segura, A. and Ferrer-Roca, Ch. and Kumar, R. S. and Tschauner, O. and Aquilantfi, G.},
title = {Crystal stability and pressure-induced phase transitions in scheelite AWO(4) (A = Ca, Sr, Ba, Pb, Eu) binary oxides. II: Towards a systematic understanding},
journal = {PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS},
year = {2007},
volume = {244},
number = {1},
pages = {295-302},
note = {12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006},
doi = {{10.1002/pssb.200672588}}
}
|
| Manjon, F.J., Gomis, O., Rodriguez-Hernandez, P., Perez-Gonzalez, E., Munoz, A., Errandonea, D., Ruiz-Fuertes, J., Segura, A., Fuentes-Cabrera, M., Tiginyanu, I.M. & Ursaki, V.V. ({2010}), "Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds" , PHYSICAL REVIEW B. , MAY 15, {2010}. Vol. {81} ({19}) |
| Abstract: A strong nonlinear pressure dependence of the optical absorption edge has been measured in defect chalcopyrites CdGa2Se4 and HgGa2Se4. The behavior is due to the nonlinear pressure dependence of the direct band-gap energy in these compounds as confirmed by ab initio calculations. Our calculations for CdGa2Se4, HgGa2Se4 and monoclinic beta-Ga2Se3 provide evidence that the nonlinear pressure dependence of the direct band-gap energy is a general feature of adamantine ordered-vacancy compounds irrespective of their composition and crystalline structure. The nonlinear behavior is due to a conduction band anticrossing at the Gamma point of the Brillouin zone caused by the presence of ordered vacancies in the unit cell of these tetrahedrally coordinated compounds. |
BibTeX:
@article{ISI:000278142000053,
author = {Manjon, F. J. and Gomis, O. and Rodriguez-Hernandez, P. and Perez-Gonzalez, E. and Munoz, A. and Errandonea, D. and Ruiz-Fuertes, J. and Segura, A. and Fuentes-Cabrera, M. and Tiginyanu, I. M. and Ursaki, V. V.},
title = {Nonlinear pressure dependence of the direct band gap in adamantine ordered-vacancy compounds},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {19},
doi = {{10.1103/PhysRevB.81.195201}}
}
|
| Manjon, F.J., Lopez-Solano, J., Ray, S., Gomis, O., Santamaria-Perez, D., Mollar, M., Panchal, V., Errandonea, D., Rodriguez-Hernandez, P. & Munoz, A. ({2010}), "High-pressure structural and lattice dynamical study of HgWO4" , PHYSICAL REVIEW B. , JUL 23, {2010}. Vol. {82} ({3}) |
| Abstract: We have synthesized monoclinic mercury tungstate (HgWO4) and characterized its structural and vibrational properties at room conditions. Additionally, we report the structural and lattice dynamical behavior of HgWO4 under high pressure studied by means of x-ray diffraction and Raman-scattering measurements up to 16 GPa and 25 GPa, respectively. The pressure dependence of the structural parameters and Raman-active first-order phonons of monoclinic C2/c HgWO4 are discussed in the light of our theoretical first-principles total-energy and lattice dynamics calculations. Our measurements show that the monoclinic phase of HgWO4 is stable up to the maximum pressure reached in these experiments. Theoretically predicted possible high-pressure phases and the theoretical pressure dependence of infrared-active modes are also reported. |
BibTeX:
@article{ISI:000280230100005,
author = {Manjon, F. J. and Lopez-Solano, J. and Ray, S. and Gomis, O. and Santamaria-Perez, D. and Mollar, M. and Panchal, V. and Errandonea, D. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {High-pressure structural and lattice dynamical study of HgWO4},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {82},
number = {3},
doi = {{10.1103/PhysRevB.82.035212}}
}
|
| Manjon, F.J., Rodriguez-Hernandez, P., Munoz, A., Romero, A.H., Errandonea, D. & Syassen, K. ({2010}), "Lattice dynamics of YVO4 at high pressures" , PHYSICAL REVIEW B. , FEB, {2010}. Vol. {81} ({7}) |
| Abstract: We report an experimental and theoretical lattice-dynamics study of yttrium orthovanadate (YVO4) up to 33 GPa together with a theoretical study of its structural stability under pressure. Raman-active modes of the zircon phase are observed up to 7.5 GPa, where the onset of an irreversible zircon-to-scheelite phase transition is detected, and Raman-active modes in the scheelite structure are observed up to 20 GPa, where a reversible second-order phase transition occurs. Our ab initio total-energy calculations support that the second-order phase transition in YVO4 is from the scheelite to the monoclinic M-fergusonite structure. The M-fergusonite structure remains up to 33 GPa and on pressure release the sample reverts back to the metastable scheelite phase. Raman-and IR-mode symmetries, frequencies, and pressure coefficients in the zircon, scheelite, and M-fergusonite phases are discussed. |
BibTeX:
@article{ISI:000274998200057,
author = {Manjon, F. J. and Rodriguez-Hernandez, P. and Munoz, A. and Romero, A. H. and Errandonea, D. and Syassen, K.},
title = {Lattice dynamics of YVO4 at high pressures},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {7},
doi = {{10.1103/PhysRevB.81.075202}}
}
|
| Marilena Toma, L., Lescouezec, R., Uriel, S., Llusar, R., Ruiz-Perez, C., Vaissermann, J., Lloret, F. & Julve, M. ({2007}), "4,2-ribbon like ferromagnetic cyano-bridged (Fe2NiII)-Ni-III chains: a magneto-structural study" , DALTON TRANSACTIONS. ({33}) , pp. {3690-3698}. |
| Abstract: The low-spin iron(III) complex AsPh4[Fe-III(bpy)(CN)4]center dot CH3CN ( 1) [AsPh4 = tetraphenylarsonium cation] and the heterobimetallic chains [Fe-III(L)(CN)(4)(2)Ni-II(H2O)(2)]center dot 4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)]anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron( III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal atom. 2 and 3 are isomorphous compounds whose structure is made up of neutral 4,2-ribbon like bimetallic chains of formula [Fe-III(L)(CN)(4)(2)Ni-II(H2O)(2)] where the [Fe-III(L)(CN)(4)](-) unit acts as a bis-monodentate bridging ligand toward the trans-diaquanickel(II) units through two of its four cyanide groups in cis positions. The chains exhibit two orientations in the unit cell and they interact with each other through hydrogen bonds involving the coordination and crystallization water molecules together with the uncoordinated cyanide nitrogen atoms of the [ Fe( L)( CN) 4]- units. Compounds 2 and 3 behave as ferromagnetic (Fe2NiII)-Ni-III chains which interact ferromagnetically at very low temperatures in the case of 2, whereas metamagnetic-like behaviour is observed for 3 with a critical field (Hc) around 200 G. For H > H-c the ferromagnetic (Fe2NiII)-Ni-III chains of 3 exhibit a frequency dependence of the out-of-phase ac susceptibility signal at T < 3.5 K. |
BibTeX:
@article{ISI:000248731300021,
author = {Marilena Toma, Luminita and Lescouezec, Rodrigue and Uriel, Santiago and Llusar, Rosa and Ruiz-Perez, Catalina and Vaissermann, Jacqueline and Lloret, Francesc and Julve, Miguel},
title = {4,2-ribbon like ferromagnetic cyano-bridged (Fe2NiII)-Ni-III chains: a magneto-structural study},
journal = {DALTON TRANSACTIONS},
year = {2007},
number = {33},
pages = {3690-3698},
doi = {{10.1039/b705084b}}
}
|
| Marrero, N., Gonzalez-Diaz, B., Guerrero-Lemus, R., Borchert, D. & Hernandez-Rodriguez, C. ({2007}), "Optimization of sodium carbonate texturization on large-area crystalline silicon solar cells" , SOLAR ENERGY MATERIALS AND SOLAR CELLS. , DEC 14, {2007}. Vol. {91} ({20}) , pp. {1943-1947}. |
| Abstract: This work describes a texturization method for monocrystalline silicon solar cells based on a mixture of sodium carbonate and sodium hydrogen carbonate solutions. A specific solution has been found that results in an optimal etching rate, the lowest surface reflectance and a homogeneous density of pyramidal structures on the silicon surface. The subsequent phosphorus diffusion with rapid thermal processes has been modified in order to drastically reduce the process time and, simultaneously, to obtain a high homogeneity of the sheet resistance values and improved photocarriers lifetimes. 100 x 100 mm solar cells with an efficiency of 15.8% have been obtained compared to an efficiency of 14.7% for the reference cell. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000250684300011,
author = {Marrero, N. and Gonzalez-Diaz, B. and Guerrero-Lemus, R. and Borchert, D. and Hernandez-Rodriguez, C.},
title = {Optimization of sodium carbonate texturization on large-area crystalline silicon solar cells},
journal = {SOLAR ENERGY MATERIALS AND SOLAR CELLS},
year = {2007},
volume = {91},
number = {20},
pages = {1943-1947},
doi = {{10.1016/j.solmat.2007.08.001}}
}
|
| Marrero, N., Guerrero-Lemus, R., Gonzalez-Diaz, B. & Borchert, D. ({2009}), "Effect of porous silicon stain etched on large area alkaline textured crystalline silicon solar cells" , THIN SOLID FILMS. , FEB 27, {2009}. Vol. {517} ({8}) , pp. {2648-2650}. |
| Abstract: This work shows the effects of porous silicon stain etched on alkaline textured antireflection coatings of large area monocrystalline silicon solar cells. The texturization process has been produced by immersion of the silicon wafers in different carbonate-based solutions. The porous silicon layers were formed by stain etching in a HNO3/HF aqueous solution before or after the texturization process. We study the effects of different alkaline and acidic solutions and the etching times on the solar cell parameters and the surface reflectance of the device. We have found that the average reflectance of the surface is lowered when the porous etching is combined with the texturization in the alkaline solution. However, the solar cell characteristics are not improved. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000263927300014,
author = {Marrero, N. and Guerrero-Lemus, R. and Gonzalez-Diaz, B. and Borchert, D.},
title = {Effect of porous silicon stain etched on large area alkaline textured crystalline silicon solar cells},
journal = {THIN SOLID FILMS},
year = {2009},
volume = {517},
number = {8},
pages = {2648-2650},
doi = {{10.1016/j.tsf.2008.09.070}}
}
|
| Marrero-Lopez, D., Nunez, P., Abril, M., Lavin, V., Rodriguez-Mendoza, U. & Rodriguez, V. ({2004}), "Synthesis, electrical properties, and optical characterization of Eu3+-doped La2Mo2O9 nanocrystalline phosphors" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , OCT 15, {2004}. Vol. {345} , pp. {377-381}. Note:10th International Conference on the Physics of Non-Crystalline Solids (PNCS), Parma, ITALY, JUL 13-17, 2003. |
| Abstract: The lanthanum molybdate phosphor, La2Mo2O9, is a new fast ionic conductor that has shown potential uses as a nanocrystalline matrix for optically active lanthanide ions. Eu3+-doped La2Mo2O9 phosphors were prepared from freeze-dried powder precursor and the nano-polycrystalline powders obtained were characterized by XRD, DSC, TG/DTA, SEM, impedance spectroscopy, and optical spectroscopy. The substitution of La3+ by Eu3+ in La2-xEuxMo2O9 suppresses partially the phase transition observed in the undoped samples and increases both the density of sintered pellets and the ionic conductivity. Polycrystalline powder and sintered pellets of La2Mo2O9 phosphor exhibits optical transitions in the UV-visible region at low temperature, although there is a luminescence quenching process with temperature. At room temperature orange and red emissions are only observed when doping with Eu3+ ions. Moreover, a nanocrystal-size dependent energy transfer process from the matrix to the Eu3+ ions occurs. (C) 2004 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000225583200073,
author = {Marrero-Lopez, D and Nunez, P and Abril, M and Lavin, V and Rodriguez-Mendoza, UR and Rodriguez, VD},
title = {Synthesis, electrical properties, and optical characterization of Eu3+-doped La2Mo2O9 nanocrystalline phosphors},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2004},
volume = {345},
pages = {377-381},
note = {10th International Conference on the Physics of Non-Crystalline Solids (PNCS), Parma, ITALY, JUL 13-17, 2003},
doi = {{10.1016/j.jnoncrysol.2004.08.047}}
}
|
| Martin, L.L., Haro-Gonzalez, P. & Martin, I.R. ({2011}), "Optical properties of transparent Dy3+ doped Ba2TiSi2O8 glass ceramic" , OPTICAL MATERIALS. , MAR, {2011}. Vol. {33} ({5, Sp. Iss. SI}) , pp. {738-741}. Note:5th Laser Ceramics Symposium - International Symposium on Transparent Ceramics for Photonics Applications, Bilbao, SPAIN, DEC 09-11, 2009. |
| Abstract: The Ba2TiSi2O8 is a well known piezoelectric, ferroelectric and non-linear crystal. Nanocrystals of Ba2TiSi2O8 doped with 1.5 Dy3+ have been obtained by thermal treatment of a precursor glass and their optical properties have been studied. X-ray diffraction patterns and optical measurements have been carried out on the precursor glass and glass ceramic samples. The emission spectra corresponding to the Dy3+: F-4(9/2) -> H-6(13/2) (575 nm), F-4(9/2) -> H-6(11/2) (670 nm) and F-4(9/2) -> H-6(9/2) (757 nm) transitions have been obtained under laser excitation at 473 nm. These measurements confirm the incorporation of the Dy3+ ions into the Ba2TiSi2O8 nanocrystals which produces an enhancement of luminescence at 575 nm. At this wavelength has been demonstrated a maximum optical amplification around 1.9 cm(-1) (similar to 8.2 dB/cm). (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000288578500016,
author = {Martin, L. L. and Haro-Gonzalez, P. and Martin, I. R.},
title = {Optical properties of transparent Dy3+ doped Ba2TiSi2O8 glass ceramic},
journal = {OPTICAL MATERIALS},
year = {2011},
volume = {33},
number = {5, Sp. Iss. SI},
pages = {738-741},
note = {5th Laser Ceramics Symposium - International Symposium on Transparent Ceramics for Photonics Applications, Bilbao, SPAIN, DEC 09-11, 2009},
doi = {{10.1016/j.optmat.2010.11.027}}
}
|
| Martin, L.L., Haro-Gonzalez, P., Martin, I.R., Navarro-Urrios, D., Alonso, D., Perez-Rodriguez, C., Jaque, D. & Capuj, N.E. ({2011}), "Whispering-gallery modes in glass microspheres: optimization of pumping in a modified confocal microscope" , OPTICS LETTERS. , MAR 1, {2011}. Vol. {36} ({5}) , pp. {615-617}. |
| Abstract: Whispering-gallery modes (WGMs) on Nd3+-doped glass microspheres with a radius of similar to 15 mu m were measured in a modified confocal microscope, where a dual spatial resolution in both excitation and detection zones was possible. As an alternative to the standard excitation mechanism by an evanescent wave, we used an efficient pumping/detecting scheme, focusing a laser in the microsphere and exciting the Nd3+ ions, whose fluorescent emission produces the WGMs. We have also measured the generated WGMs by changing the detection zone, where higher amplitude resonances were found when exciting in the center and detecting at the edge of the microsphere. (C) 2011 Optical Society of America |
BibTeX:
@article{ISI:000287912500007,
author = {Martin, L. L. and Haro-Gonzalez, P. and Martin, I. R. and Navarro-Urrios, D. and Alonso, D. and Perez-Rodriguez, C. and Jaque, D. and Capuj, N. E.},
title = {Whispering-gallery modes in glass microspheres: optimization of pumping in a modified confocal microscope},
journal = {OPTICS LETTERS},
year = {2011},
volume = {36},
number = {5},
pages = {615-617}
}
|
| Martin, L.L., Haro-Gonzalez, P., Martin, I.R., Puerto, D., Solis, J., Caceres, J.M. & Capuj, N.E. ({2010}), "Local devitrification of Dy3+ doped Ba2TiSi2O8 glass by laser irradiation" , OPTICAL MATERIALS. , DEC, {2010}. Vol. {33} ({2}) , pp. {186-190}. Note:Workshop on International Commission on Glass, Florence, ITALY, APR 28-30, 2010. |
| Abstract: The Ba2TiSi2O8 (BTS) is a well known piezoelectric, ferroelectric and non-linear crystal. In this work, nanocrystals of BTS have been obtained by different thermal treatments of precursor glasses. The glasses were fabricated from BaO-TiO2-SiO2 and doped with Dy2O3 using the melt quenching method. Thermal treatment in an electrical furnace at 740 degrees C was used to obtain transparent glass ceramic samples, which are formed by an amorphous matrix containing BTS nanocrystals, with an average size of 35 nm confirmed by X-ray diffraction. Moreover, a localized area in the precursor glass has been irradiated by continuous wave (c.w.) Ar-laser or femtosecond (fs) pulsed laser. Evidence of the changes induced by laser irradiation is confirmed by spectroscopic comparison of irradiated regions with the precursor glass and glass ceramic samples. The emission spectra corresponding to the Dy3+: F-4(9/2) -> H-6(13/2) (578 nm), F-4(9/2) -> H-6(1/12) (670 nm) and F-4(9/2) -> H-6(9/2) (757 nm) transitions were obtained under laser excitation at 473 nm. These measurements confirm the incorporation of the Dy3+ ions into the BTS nanocrystals which produces an enhancement of luminescence and makes it an attractive material for optical amplification. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000288284400016,
author = {Martin, L. L. and Haro-Gonzalez, P. and Martin, I. R. and Puerto, D. and Solis, J. and Caceres, J. M. and Capuj, N. E.},
title = {Local devitrification of Dy3+ doped Ba2TiSi2O8 glass by laser irradiation},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {33},
number = {2},
pages = {186-190},
note = {Workshop on International Commission on Glass, Florence, ITALY, APR 28-30, 2010},
doi = {{10.1016/j.optmat.2010.09.032}}
}
|
| Martinez-Lillo, J., Delgado, F.S., Ruiz-Perez, C., Lloret, F., Julve, M. & Faus, J. ({2007}), "Heterotrimetallic oxalato-bridged (Re2MII)-M-IV complexes (M = Mn, Co, Ni, Cu): Synthesis, crystal structure, and magnetic properties" , INORGANIC CHEMISTRY. , APR 30, {2007}. Vol. {46} ({9}) , pp. {3523-3530}. |
| Abstract: The use of the (NBu4)(2)[(ReCl4)-Cl-IV(ox)] mononuclear species as a ligand toward divalent first row transition metal ions in the presence of imidazole affords the new trinuclear compounds of formula (NBu4)(2)[(ReCl4)-Cl-IV(mu-ox)(2)M-II(Him)(2)] [NBu4+ = tetra-n-butylammonium cation, ox = oxalate dianion, Him = imidazole; M = Mn (1), Co (2), Ni (3), Cu (4)] whose preparation, crystal structures, and magnetic properties are reported. 1-4 are isostructural complexes which are made up of discrete trinuclear [(ReCl4)-Cl-IV(mu-ox)(2)M-II(Him)(2)](2-) anions and bulky NBu4+ cations. The Re and M atoms exhibit somewhat distorted octahedral surroundings which are built by four chloro and two oxalate oxygens (Re) and two imidazole nitrogen and four oxalate oxygen atoms (M), the central M atom being linked to the two peripheral Re atoms through bis-bidentate oxalate. The values of the Re center dot center dot center dot M separation across bridging oxalate vary in the range 5.646(2) (M = Ni) to 5.794(2) angstrom (M = Mn). Magnetic susceptibility measurements on polycrystalline samples of 1-4 in the temperature range 1.9-300 K show the occurrence of significant intramolecular antiferro- (1) and ferromagnetic (2-4) interactions. The nature and magnitude of the magnetic coupling in 1-4 are qualitatively understood through orbital symmetry considerations. |
BibTeX:
@article{ISI:000245871700015,
author = {Martinez-Lillo, Jose and Delgado, Fernado S. and Ruiz-Perez, Catalina and Lloret, Francesc and Julve, Miguel and Faus, Juan},
title = {Heterotrimetallic oxalato-bridged (Re2MII)-M-IV complexes (M = Mn, Co, Ni, Cu): Synthesis, crystal structure, and magnetic properties},
journal = {INORGANIC CHEMISTRY},
year = {2007},
volume = {46},
number = {9},
pages = {3523-3530},
doi = {{10.1021/ic0622095}}
}
|
| Mateo, A.M. & Delgado, V. ({2008}), "Effective mean-field equations for cigar-shaped and disk-shaped Bose-Einstein condensates" , PHYSICAL REVIEW A. , JAN, {2008}. Vol. {77} ({1}) |
| Abstract: By applying the standard adiabatic approximation and using the accurate analytical expression for the corresponding local chemical potential obtained in our previous work [Phys. Rev. A 75, 063610 (2007)] we derive an effective 1D equation that governs the axial dynamics of mean-field cigar-shaped condensates with repulsive interatomic interactions, accounting accurately for the contribution from the transverse degrees of freedom. This equation, which is more simple than previous proposals, is also more accurate. Moreover, it allows treating condensates containing an axisymmetric vortex with no additional cost. Our effective equation also has the correct limit in both the quasi-1D mean-field regime and the Thomas-Fermi regime and permits one to derive fully analytical expressions for ground-state properties such as the chemical potential, axial length, axial density profile, and local sound velocity. These analytical expressions remain valid and accurate in between the above two extreme regimes. Following the same procedure we also derive an effective 2D equation that governs the transverse dynamics of mean-field disk-shaped condensates. This equation, which also has the correct limit in both the quasi-2D and the Thomas-Fermi regime, is again more simple and accurate than previous proposals. We have checked the validity of our equations by numerically solving the full 3D Gross-Pitaevskii equation. |
BibTeX:
@article{ISI:000252862000147,
author = {Mateo, A. Munoz and Delgado, V.},
title = {Effective mean-field equations for cigar-shaped and disk-shaped Bose-Einstein condensates},
journal = {PHYSICAL REVIEW A},
year = {2008},
volume = {77},
number = {1},
doi = {{10.1103/PhysRevA.77.013617}}
}
|
| Mateo, A.M. & Delgado, V. ({2006}), "Extension of the Thomas-Fermi approximation for trapped Bose-Einstein condensates with an arbitrary number of atoms" , PHYSICAL REVIEW A. , DEC, {2006}. Vol. {74} ({6}) |
| Abstract: By incorporating the zero-point energy contribution we derive simple and accurate extensions of the usual Thomas-Fermi (TF) expressions for the ground-state properties of trapped Bose-Einstein condensates that remain valid for an arbitrary number of atoms in the mean-field regime. Specifically, we obtain approximate analytical expressions for the ground-state properties of spherical, cigar-shaped, and disk-shaped condensates that reduce to the correct analytical formulas in both the TF and the perturbative regimes, and remain valid and accurate in between these two limiting cases. Mean-field quasi-one-dimensional (quasi-1D) and -2D condensates appear as simple particular cases of our formulation. The validity of our results is corroborated by an independent numerical computation based on the 3D Gross-Pitaevskii equation. |
BibTeX:
@article{ISI:000243166700183,
author = {Mateo, A. Munoz and Delgado, V.},
title = {Extension of the Thomas-Fermi approximation for trapped Bose-Einstein condensates with an arbitrary number of atoms},
journal = {PHYSICAL REVIEW A},
year = {2006},
volume = {74},
number = {6},
doi = {{10.1103/PhysRevA.74.065602}}
}
|
| Mateo, A.M., Delgado, V. & Malomed, B.A. ({2011}), "Gap solitons in elongated geometries: The one-dimensional Gross-Pitaevskii equation and beyond" , PHYSICAL REVIEW A. , MAY 9, {2011}. Vol. {83} ({5}) |
| Abstract: We report results of a systematic analysis of matter-wave gap solitons (GSs) in three-dimensional self-repulsive Bose-Einstein condensates (BECs) loaded into a combination of a cigar-shaped trap and axial optical-lattice (OL) potential. Basic cases of the strong, intermediate, and weak radial (transverse) confinement are considered, as well as settings with shallow and deep OL potentials. Only in the case of the shallow lattice combined with tight radial confinement, which actually has little relevance to realistic experimental conditions, does the usual one-dimensional (1D) cubic Gross-Pitaevskii equation (GPE) furnish a sufficiently accurate description of GSs. However, the effective 1D equation with the nonpolynomial nonlinearity, derived in Ref. [Phys. Rev. A 77, 013617 (2008)], provides for quite an accurate approximation for the GSs in all cases, including the situation with weak transverse confinement, when the soliton's shape includes a considerable contribution from higher-order transverse modes, in addition to the usual ground-state wave function of the respective harmonic oscillator. Both fundamental GSs and their multipeak bound states are considered. The stability is analyzed by means of systematic simulations. It is concluded that almost all the fundamental GSs are stable, while their bound states may be stable if the underlying OL potential is deep enough. |
BibTeX:
@article{ISI:000290384600007,
author = {Mateo, A. Munoz and Delgado, V. and Malomed, Boris A.},
title = {Gap solitons in elongated geometries: The one-dimensional Gross-Pitaevskii equation and beyond},
journal = {PHYSICAL REVIEW A},
year = {2011},
volume = {83},
number = {5},
doi = {{10.1103/PhysRevA.83.053610}}
}
|
| Mendez-Ramos, J., Abril, M., Martin, I., Rodriguez-Mendoza, U., Lavin, V., Rodriguez, V., Nunez, P. & Lozano-Gorrin, A. ({2006}), "Ultraviolet and visible upconversion luminescence in Nd3+-doped oxyfluoride glasses and glass ceramics obtained by different preparation methods" , JOURNAL OF APPLIED PHYSICS. , JUN 1, {2006}. Vol. {99} ({11}) |
| Abstract: Ultraviolet and visible upconversion emissions under infrared excitation have been obtained and compared in Nd3+-doped oxyfluoride glasses and glass ceramics prepared by different methods. The mechanisms involved in such processes have been analyzed. A spectroscopy study comparing absorption and upconversion excitation spectra has been carried out in order to discern in each case the mechanism involved in the origin of the upconversion emissions, i.e., two- or three-photon involved excited state absorption or energy transfer processes. The shape of the absorption and emission spectra and the relative upconversion efficiencies have been compared and explained taking into account the final distribution of the luminescent ions in the glassy and nanocrystalline phases. (c) 2006 American Institute of Physics. |
BibTeX:
@article{ISI:000238314900026,
author = {Mendez-Ramos, J and Abril, M and Martin, IR and Rodriguez-Mendoza, UR and Lavin, V and Rodriguez, VD and Nunez, P and Lozano-Gorrin, AD},
title = {Ultraviolet and visible upconversion luminescence in Nd3+-doped oxyfluoride glasses and glass ceramics obtained by different preparation methods},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2006},
volume = {99},
number = {11},
doi = {{10.1063/1.2203395}}
}
|
| Mendez-Ramos, J., Rodriguez, V.D., Tikhomirov, V.K., del Castillo, J. & Yanes, A.C. ({2008}), "Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics tuneable up-conversion phosphor" , EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS. , AUG, {2008}. Vol. {43} ({2}) , pp. {149-153}. |
| Abstract: Transparent Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics have been prepared, 32(SiO2) 9(AlO1.5) 31.5(CdF2) 18.5(PbF2) 5.5(ZnF2): 3.5(Yb-Er-TmF3) mol where the co-dopants partition mostly to the fluoride PbF2-based nano-crystals. A comparative study of the up-conversion luminescence in nano-glass-ceramics and its precursor glass indicates that these materials can be used as blue/green/red tuneable up-conversion phosphor, in particular for white light generation. A ratio between blue, green and red emission bands of the Tm3+ and Er3+ can be widely varied with nano-ceramming of the precursor glass and with changing a pump power of luminescence. The change in the ratio between the blue, green and red emission bands is explained to be due to substantial lowering phonon energy and shortening of inter-dopant distances with nano-ceramming of the precursor glass and due to change in the ratio of 2- and 3-photon up-conversion processes with pump power. |
BibTeX:
@article{ISI:000258652100002,
author = {Mendez-Ramos, J. and Rodriguez, V. D. and Tikhomirov, V. K. and del-Castillo, J. and Yanes, A. C.},
title = {Yb3+-Er3+-Tm3+ co-doped nano-glass-ceramics tuneable up-conversion phosphor},
journal = {EUROPEAN PHYSICAL JOURNAL-APPLIED PHYSICS},
year = {2008},
volume = {43},
number = {2},
pages = {149-153},
doi = {{10.1051/epjap:2008101}}
}
|
| Mendez-Ramos, J., Santana-Alonso, A., Yanes, A.C., del Castillo, J. & Rodriguez, V.D. ({2010}), "Rare-earth doped YF3 nanocrystals embedded in sol-gel silica glass matrix for white light generation" , JOURNAL OF LUMINESCENCE. , DEC, {2010}. Vol. {130} ({12}) , pp. {2508-2511}. |
| Abstract: YF3 nanocrystals triply-doped with Yb3+, Ho3+ and Tm3+ ions embedded in amorphous silica matrix have been successfully obtained by heat treatment of precursor sol-gel glasses for the first time to our knowledge and confirmed by X-ray diffraction and luminescence measurements. Simultaneous UV and visible efficient up-conversion emissions, with well-resolved Stark structure, under 980 nm infrared pump are observed, indicating the effective partition of rare-earth ions into a crystalline-like environment of the YF3 nanocrystals. Corresponding energy transfer mechanisms have been analyzed and overall colour emission has been quantified in terms of standard chromaticity diagram. By an adequate doping level and heat treatment temperature of precursor sol-gel glasses, a bright white colour has been accomplished, close to the standard equal energy white light illumination point, with potential applications in photo-electronic devices and information processing. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000284135400039,
author = {Mendez-Ramos, J. and Santana-Alonso, A. and Yanes, A. C. and del-Castillo, J. and Rodriguez, V. D.},
title = {Rare-earth doped YF3 nanocrystals embedded in sol-gel silica glass matrix for white light generation},
journal = {JOURNAL OF LUMINESCENCE},
year = {2010},
volume = {130},
number = {12},
pages = {2508-2511},
doi = {{10.1016/j.jlumin.2010.08.027}}
}
|
| Mendez-Ramos, J., Tikhomirov, V.K., Rodriguez, V.D. & Furniss, D. ({2007}), "Infrared tuneable up-conversion phosphor based on Er3+-doped nano-glass-ceramics" , JOURNAL OF ALLOYS AND COMPOUNDS. , AUG 16, {2007}. Vol. {440} ({1-2}) , pp. {328-332}. |
| Abstract: Up-conversion luminescence has been studied in the Er3+ -doped oxyfluoride glass, its daughter nano-glass-ceramics and the polycrystalline ErF3 when excited at infrared wavelengths of either 800 or 980 nm. The mechanism of the up-conversion luminescence is shown to differ for excitations at 800 and 980 nm since the different excited levels of the Er3+ are involved, respectively. An order of magnitude increase of red-to-green up-conversion luminescence ratio has been observed with nano-ceramming of the precursor glass when excited at 800 nm and a full dominance of the red up-conversion luminescence has been observed in the ErF3 at the both excitation wavelengths. Observed changes in the spectra of the up-conversion luminescence from the precursor glass to its daughter nano-glass-ceramics provide a tool for tuning the colour of the up-conversion luminescence by ceramming of the precursor glass. These changes are shown to be due to decrease of the vibration energy of phonons coupled to the Er3+ ions embedded to the PbF2 nano-crystals with nano-ceramming. Hence we report for the first time that the red up-conversion luminescence from the Er3+ -doped material can be due to the radiative transition F-4(5/2), F-4(3/2) -> I-4(13/2) of the Er3+ ion, which is principally allowed only in such a low-phonon energy host as the PbF2 nano-crystals, while such red up-conversion luminescence is almost completely non-radiatively quenched in the oxyfluoride precursor glass. The up-conversion emission spectrum of the ErF3 is dominated by a cross-relaxation mechanism typical of hosts with a very high doping level of the Er3+ ions. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000248028300065,
author = {Mendez-Ramos, J. and Tikhomirov, V. K. and Rodriguez, V. D. and Furniss, D.},
title = {Infrared tuneable up-conversion phosphor based on Er3+-doped nano-glass-ceramics},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2007},
volume = {440},
number = {1-2},
pages = {328-332},
doi = {{10.1016/j.jallcom.2006.09.033}}
}
|
| Mendez-Ramos, J., Velazquez, J.J., Yanes, A.C., del Castillo, J. & Rodriguez, V.D. ({2008}), "Up-conversion in nanostructured Yb3+-Tm3+ co-doped sol-gel derived SiO2-LaF3 transparent glass-ceramics" , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. , FEB, {2008}. Vol. {205} ({2}) , pp. {330-334}. |
| Abstract: Nanostructured transparent glass-ceramics with composition of 95SiO(2)-5LaF(3) doped with 0.1 mol% of Tm(3+)or co-doped with 0.1 mol% of Tm3+ and 0.3 mol% of Yb3+ were synthesized by thermal treatment of precursor sol-gel derived glasses. A comparative luminescence analysis in terms of different temperatures of thermal treatments has been carried out. Segregation of LaF3 nanocrystals in the matrix was con-firmed by X-ray diffraction. Blue and red efficient up-conversion emissions were observed under 980 nm excitation at room temperature. These results indicate partition of a significant fraction of co-dopants into the precipitated LaF3 nanocrystals. The mechanisms involved in the up-conversion emissions have been analyzed and can be ascribed to processes with two, three and four photons. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
BibTeX:
@article{ISI:000253551000019,
author = {Mendez-Ramos, J. and Velazquez, J. J. and Yanes, A. C. and del-Castillo, J. and Rodriguez, V. D.},
title = {Up-conversion in nanostructured Yb3+-Tm3+ co-doped sol-gel derived SiO2-LaF3 transparent glass-ceramics},
journal = {PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE},
year = {2008},
volume = {205},
number = {2},
pages = {330-334},
doi = {{10.1002/pssa.200723296}}
}
|
| Mendez-Ramos, J., Yanes, A.C., Santana-Alonso, A., del Castillo, J. & Rodriguez, V.D. ({2010}), "Colour Tuneability in Sol-Gel Nano-Glass-Ceramics Comprising Yb3+-Er3+-Tm3+ Co-Doped NaYF4 Nanocrystals" , JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. , FEB, {2010}. Vol. {10} ({2}) , pp. {1273-1277}. Note:International Conference on Surface, Coatings and Nanostructured Materials, Barcelona, SPAIN, OCT 21-24, 2008. |
| Abstract: White light can be obtained by up-conversion processes in a cheap and efficient way, being of great interest for lighting, displays, and photonic integrated devices. Here we report a generation of white light under 980 nm laser infrared excitation in Yb3+-Er3+-Tm3+ triply doped sol-gel derived nano-glass-ceramics containing NaYF4 nanocrystals where co-dopants ions are partitioned. Efficient simultaneous blue, green, and red up-conversion emissions give rise to a balanced white overall emission and corresponding up-conversion mechanisms have been analyzed. Changes in pump power intensity or heat treatment temperature widely vary the ratio of emission bands, resulting in a colour tuneability which has been analyzed and quantified in terms of CIE standard chromaticity diagram. |
BibTeX:
@article{ISI:000273709900087,
author = {Mendez-Ramos, J. and Yanes, A. C. and Santana-Alonso, A. and del-Castillo, J. and Rodriguez, V. D.},
title = {Colour Tuneability in Sol-Gel Nano-Glass-Ceramics Comprising Yb3+-Er3+-Tm3+ Co-Doped NaYF4 Nanocrystals},
journal = {JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY},
year = {2010},
volume = {10},
number = {2},
pages = {1273-1277},
note = {International Conference on Surface, Coatings and Nanostructured Materials, Barcelona, SPAIN, OCT 21-24, 2008},
doi = {{10.1166/jnn.2010.1871}}
}
|
| Montesdeoca-Santana, A., Jimenez-Rodriguez, E., Marrero, N., Gonzalez-Diaz, B., Borchert, D. & Guerrero-Lemus, R. ({2010}), "XPS characterization of different thermal treatments in the ITO-Si interface of a carbonate-textured monocrystalline silicon solar cell" , NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS. , FEB, {2010}. Vol. {268} ({3-4}) , pp. {374-378}. Note:Spring Meeting of the European-Materials-Research-Society, Strasbourg, FRANCE, JUN 08-12, 2009. |
| Abstract: In this work we have applied the X-ray pholoelectron spectroscopy (XPS) in depth to study, for the first time, the influence of different thermal treatments in the ITO-Si interface of a monocrystalline Si-based solar cell where the Si surface is carbonate-textured and covered by an ITO sputtered layer. The efficiency of the solar cells significantly increases when thermal treatments are applied just after the ITO deposition. The efficiency is also dependent on the characteristics of the pyramidal relief of the silicon surface previously obtained by immersion of the Si wafers in a sodium carbonate/bicarbonate solution. An efficiency of 15.5% has been obtained with an optimized texturization of the silicon substrates and an annealing treatment of the solar cells at 400 degrees C just after the ITO deposition. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000275360100031,
author = {Montesdeoca-Santana, A. and Jimenez-Rodriguez, E. and Marrero, N. and Gonzalez-Diaz, B. and Borchert, D. and Guerrero-Lemus, R.},
title = {XPS characterization of different thermal treatments in the ITO-Si interface of a carbonate-textured monocrystalline silicon solar cell},
journal = {NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS},
year = {2010},
volume = {268},
number = {3-4},
pages = {374-378},
note = {Spring Meeting of the European-Materials-Research-Society, Strasbourg, FRANCE, JUN 08-12, 2009},
doi = {{10.1016/j.nimb.2009.09.044}}
}
|
| Monzon Mayor, M., Romero-Aleman, M.D.M., Montesdeoca, S., Santos, E., Yanes, C. & Lang, D. ({2009}), "IMMUNOHISTOCHEMICAL STUDY OF THE EXPRESSION OF THE P75 NEUROTROPHIN RECEPTOR IN THE CONTROL AND REGENERATION OPTIC NERVE OF THE LIZARD GALLOTIA GALLOTI" , GLIA. , OCT, {2009}. Vol. {57} ({13, Suppl. S}) , pp. {S155-S156}. Note:9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009. |
BibTeX:
@article{ISI:000270075500639,
author = {Monzon Mayor, M. and Romero-Aleman, M. D. M. and Montesdeoca, S. and Santos, E. and Yanes, C. and Lang, D.},
title = {IMMUNOHISTOCHEMICAL STUDY OF THE EXPRESSION OF THE P75 NEUROTROPHIN RECEPTOR IN THE CONTROL AND REGENERATION OPTIC NERVE OF THE LIZARD GALLOTIA GALLOTI},
journal = {GLIA},
year = {2009},
volume = {57},
number = {13, Suppl. S},
pages = {S155-S156},
note = {9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009}
}
|
| Munoz Mateo, A. & Delgado, V. ({2009}), "Effective one-dimensional dynamics of elongated Bose-Einstein condensates" , ANNALS OF PHYSICS. , MAR, {2009}. Vol. {324} ({3}) , pp. {709-724}. |
| Abstract: By using a variational approach in combination with the adiabatic approximation we derive a new effective I D equation of motion for the axial dynamics of elongated condensates. For condensates with vorticity vertical bar q vertical bar = 0 or 1, this equation coincides with our previous proposal [A. Munoz Mateo, V. Delgado, Phys. Rev. A 77 (2008) 013617]. We also rederive the nonpolynomial Schrodinger equation (NPSE) in terms of the adiabatic approximation. This provides a unified treatment for obtaining the different effective equations and allows appreciating clearly the differences and similarities between the various proposals. We also obtain an expression for the axial healing length of cigar-shaped condensates and show that, in the local density approximation and in units of the axial oscillator length, it coincides with the inverse of the condensate axial half-length. From this result it immediately follows the necessary condition for the validity of the local density approximation. Finally, we obtain analytical formulas that give the frequency of the axial breathing mode with accuracy better than 1 These formulas can be relevant from an experimental point of view since they can be expressed in terms only of the axial half-length and remain valid in the crossover between the Thomas-Fermi and the quasi-1D mean-field regimes. We have corroborated the validity of our results by numerically solving the full 3D Gross-Pitaevskii equation. (C) 2008 Elsevier Inc. All rights reserved. |
BibTeX:
@article{ISI:000263849400008,
author = {Munoz Mateo, A. and Delgado, V.},
title = {Effective one-dimensional dynamics of elongated Bose-Einstein condensates},
journal = {ANNALS OF PHYSICS},
year = {2009},
volume = {324},
number = {3},
pages = {709-724},
doi = {{10.1016/j.aop.2008.10.002}}
}
|
| Munoz Mateo, A. & Delgado, V. ({2007}), "Ground-state properties of trapped Bose-Einstein condensates: Extension of the Thomas-Fermi approximation" , PHYSICAL REVIEW A. , JUN, {2007}. Vol. {75} ({6}) |
| Abstract: We derive general approximate formulas that provide with remarkable accuracy the ground-state properties of any mean-field scalar Bose-Einstein condensate with short-range repulsive interatomic interactions, confined in arbitrary cylindrically symmetric harmonic traps. Our formulation is even applicable for condensates containing a multiply quantized axisymmetric vortex. We have checked the validity of our formulas by numerically solving the three-dimensional Gross-Pitaevskii equation. |
BibTeX:
@article{ISI:000247624300153,
author = {Munoz Mateo, A. and Delgado, V.},
title = {Ground-state properties of trapped Bose-Einstein condensates: Extension of the Thomas-Fermi approximation},
journal = {PHYSICAL REVIEW A},
year = {2007},
volume = {75},
number = {6},
doi = {{10.1103/PhysRevA.75.063610}}
}
|
| Munoz Mateo, A. & Delgado, V. ({2006}), "Dynamical evolution of a doubly quantized vortex imprinted in a Bose-Einstein condensate" , PHYSICAL REVIEW LETTERS. , NOV 3, {2006}. Vol. {97} ({18}) |
| Abstract: The recent experiment by Shin et al. [Phys. Rev. Lett. 93, 160406 (2004)] on the decay of a doubly quantized vortex is analyzed by numerically solving the Gross-Pitaevskii equation. Our results demonstrate that the vortex decay is mainly a consequence of dynamical instability. The monotonic increase observed in the vortex lifetimes is a consequence of the fact that the measured lifetimes incorporate the time it takes for the initial perturbation to reach the central slice. When considered locally, the splitting occurs approximately at the same time in every condensate. |
BibTeX:
@article{ISI:000241757600009,
author = {Munoz Mateo, A. and Delgado, V.},
title = {Dynamical evolution of a doubly quantized vortex imprinted in a Bose-Einstein condensate},
journal = {PHYSICAL REVIEW LETTERS},
year = {2006},
volume = {97},
number = {18},
doi = {{10.1103/PhysRevLett.97.180409}}
}
|
| Munoz Mateo, A., Delgado, V. & Malomed, B.A. ({2010}), "Three-dimensional gap solitons in Bose-Einstein condensates supported by one-dimensional optical lattices" , PHYSICAL REVIEW A. , NOV 8, {2010}. Vol. {82} ({5}) |
| Abstract: We study fundamental and compound gap solitons (GSs) of matter waves in one-dimensional (1D) optical lattices (OLs) in a three-dimensional (3D) weak-radial-confinement regime, which corresponds to realistic experimental conditions in Bose-Einstein condensates (BECs). In this regime GSs exhibit nontrivial radial structures. Associated with each 3D linear spectral band exists a family of fundamental gap solitons that share a similar transverse structure with the Bloch waves of the corresponding linear band. GSs with embedded vorticity m may exist inside bands corresponding to other values of m. Stable GSs, both fundamental and compound ones (including vortex solitons), are those which originate from the bands with lowest axial and radial quantum numbers. These findings suggest a scenario for the experimental generation of robust GSs in 3D settings. |
BibTeX:
@article{ISI:000283922100010,
author = {Munoz Mateo, A. and Delgado, V. and Malomed, Boris A.},
title = {Three-dimensional gap solitons in Bose-Einstein condensates supported by one-dimensional optical lattices},
journal = {PHYSICAL REVIEW A},
year = {2010},
volume = {82},
number = {5},
doi = {{10.1103/PhysRevA.82.053606}}
}
|
| Munoz-Santiuste, J.E., Rodriguez-Mendoza, U.R., Gonzalez-Platas, J. & Lavin, V. ({2009}), "Structural study of the Eu3+ environments in fluorozirconate glasses: Role of the temperature-induced and the pressure-induced phase transition processes in the development of a rare earth's local structure model" , JOURNAL OF CHEMICAL PHYSICS. , APR 21, {2009}. Vol. {130} ({15}) |
| Abstract: The correlation between the optical properties of the Eu3+ ions and their local structures in fluorozirconate glasses and glass-ceramics have been analyzed by means of steady-state and time-resolved site-selective laser spectroscopies. Changes in the crystal-field interaction, ranging from weak to medium strength values, are observed monitoring the luminescence and the lifetime of the Eu3+ ions in different local environments in the glass. As key roles in this study, the Eu3+ luminescence in the thermally-induced crystallization of the glass and the pressure-induced amorphization of the crystalline phase of the glass-ceramic experimentally states the existence of a parent local structure for the Eu3+ ions in the glass, identified as the EuZrF7 crystalline phase. Starting from the ab initio single overlap model, crystal-field calculations have been performed in the glass and the glass-ceramic. From the site-selective measurements, the crystal-field parameters sets are obtained, giving a suitable simulation of the F-7(J) (J=0-6) Stark energy level diagram for the Eu3+ ions in the different environments present in the fluorozirconate glass. A simple geometrical model based on a continuous distortion of the parent structure is proposed for the distribution of local environments of the Eu3+ ions in the fluorozirconate glass. |
BibTeX:
@article{ISI:000265486300027,
author = {Munoz-Santiuste, Juan E. and Rodriguez-Mendoza, Ulises R. and Gonzalez-Platas, Javier and Lavin, Victor},
title = {Structural study of the Eu3+ environments in fluorozirconate glasses: Role of the temperature-induced and the pressure-induced phase transition processes in the development of a rare earth's local structure model},
journal = {JOURNAL OF CHEMICAL PHYSICS},
year = {2009},
volume = {130},
number = {15},
doi = {{10.1063/1.3100770}}
}
|
| Nastase, S., Maxim, C., Andruh, M., Cano, J., Ruiz-Perez, C., Faus, J., Lloret, F. & Julve, M. ({2011}), "New cyanide-bridged Mn-III-M-III heterometallic dinuclear complexes constructed from [M-III(AA)(CN)(4)](-) building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties" , DALTON TRANSACTIONS. Vol. {40} ({18}) , pp. {4898-4908}. |
| Abstract: Three Mn-III-M-III (M = Cr and Fe) dinuclear complexes have been obtained by assembling [Mn-III(SB)(H2O)](+) and [M-III(AA)(CN)(4)](-) ions, where SB is the dianion of the Schiff-base resulting from the condensation of 3-methoxysalicylaldehyde with ethylenediamine (3-MeOsalen(2-)) or 1,2-cyclohexanediamine (3-MeOsalcyen(2-)):[Mn(3-MeOsalen)(H2O)(mu-NC)Cr(bipy)(CN)(3)]center dot 2H(2)O (1), [Mn(3-MeOsalen)(H2O)(mu-NC)Cr(ampy)(CN)(3)][Mn(3-MeOsalen)(H2O)(2)]C lO4 center dot 2H(2)O (2) and [Mn(3-MeOsalcyen)(H2O)(mu-NC)Fe(bpym)(CN)(3)]center dot 3H(2)O (3) (bipy = 2,2'-bipyridine, ampy = 2-aminomethylpyridine and bpym = 2,2'-bipyrimidine). The [M(AA)(CN)4](-) unit in 1-3 acts as a monodentate ligand towards the manganese(III) ion through one of its four cyanide groups. The manganese(III) ion in 1-3 exhibits an elongated octahedral stereochemistry with the tetradentate SB building the equatorial plane and a water molecule and a cyanide-nitrogen atom filling the axial positions. Remarkably, the neutral mononuclear complex [Mn(3-MeOsalen)(H2O)(2)]ClO4 co-crystallizes with the heterobimetallic unit in 2. The values of the Mn-III-M-III distance across the bridging cyanide are 5.228 (1), 5.505 (2) and 5.265 angstrom (3). The packing of the neutral heterobimetallic units in the crystal is governed by the self-complementarity of the [Mn(SB)(H2O)](+) moieties, which interact each other through hydrogen bonds established between the aqua ligand from one fragment with the set of phenolate-and methoxy-oxygens from the adjacent one. The magnetic properties of the three complexes have been investigated in the temperature range 1.9-300 K. Weak antiferromagnetic interactions between the Mn-III and M-III ions across the cyanido bridge were found: J(MnM) = -5.6 (1), -0.63 (2) and -2.4 cm(-1) (3) the Hamiltonian being defined as H = -JS(Mn)center dot S-M. Theoretical calculations based on density functional theory (DFT) have been used to substantiate both the nature and magnitude of the exchange interactions observed and also to analyze the dependence of the magnetic coupling on the structural parameters within the Mn-III-N-C-M-III motif in 1-3. |
BibTeX:
@article{ISI:000289732600024,
author = {Nastase, Silviu and Maxim, Catalin and Andruh, Marius and Cano, Joan and Ruiz-Perez, Catalina and Faus, Juan and Lloret, Francesc and Julve, Miguel},
title = {New cyanide-bridged Mn-III-M-III heterometallic dinuclear complexes constructed from [M-III(AA)(CN)(4)](-) building blocks (M = Cr and Fe): synthesis, crystal structures and magnetic properties},
journal = {DALTON TRANSACTIONS},
year = {2011},
volume = {40},
number = {18},
pages = {4898-4908},
doi = {{10.1039/c0dt01815e}}
}
|
| Navarro-Urrios, D., Ghulinyan, M., Bettotti, P., Rigo, E., Oton, C.J., Capuj, N.E., Lahoz, F., Martin, I.R. & Pavesi, L. ({2009}), "Polymeric waveguides using oxidized porous silicon cladding for optical amplification" , OPTICAL MATERIALS. , AUG, {2009}. Vol. {31} ({10, Sp. Iss. SI}) , pp. {1488-1491}. |
| Abstract: We report on a new hybrid approach to realize optical slab waveguides for optical amplification purposes. The structure consists of a dye-doped polymer core (PMMA) deposited over an oxidized porous silicon (PS) cladding layer formed on a silicon wafer. The very low refractive index (n = 1.16) achievable in the cladding allows obtaining monomodal behavior with high confinement factors (Gamma(TE) = 96 even for very thin cores (400 nm). Optically excited guided luminescence shows stimulated emission, strong line narrowing and a clear threshold and superlinear behavior with pump energy. By means of the variable stripe length (VSL) technique, values of net optical gain up to 113 dB/cm (constant over 3 mm) and absolute amplification values up to 34 dB have been measured at 694 nm when pumping with 80 mJ/cm(2) energy pulses. These results validate the use of oxidized PS as a cladding layer in silicon photonics. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000269235100022,
author = {Navarro-Urrios, D. and Ghulinyan, M. and Bettotti, P. and Rigo, E. and Oton, C. J. and Capuj, N. E. and Lahoz, F. and Martin, I. R. and Pavesi, L.},
title = {Polymeric waveguides using oxidized porous silicon cladding for optical amplification},
journal = {OPTICAL MATERIALS},
year = {2009},
volume = {31},
number = {10, Sp. Iss. SI},
pages = {1488-1491},
doi = {{10.1016/j.optmat.2009.02.008}}
}
|
| Navarro-Urrios, D., Ghulinyan, M., Capuj, N.E., Oton, C.J., Riboli, F., Martin, I.R. & Pavesi, L. ({2007}), "Waveguiding, absorption and emission properties of dye-impregnated oxidized porous silicon" , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. , MAY, {2007}. Vol. {204} ({5}) , pp. {1502-1506}. Note:5th International Conference on Porous Semiconductors - Science and Technology, Sitges, SPAIN, MAR 12-17, 2006. |
| Abstract: The waveguiding, absorption and emission properties of oxidised porous silicon waveguides when impregnated with Nile Blue have been studied. We present m-line measurements before and after the impregnation showing that the effective indices of the modes remain the same. When performing guided luminescence experiments, a structured emission band is measured. Using the refractive index profile extracted from m-line measurements it has been possible to simulate the emission lineshape assuming the observation of an interference pattern formed across the waveguide. We demonstrate that these oscillations appear because in the first hundreds of nanometers the dye concentration is several orders of magnitude higher than in the rest of the sample. |
BibTeX:
@article{ISI:000246642300052,
author = {Navarro-Urrios, D. and Ghulinyan, M. and Capuj, N. E. and Oton, C. J. and Riboli, F. and Martin, I. R. and Pavesi, L.},
title = {Waveguiding, absorption and emission properties of dye-impregnated oxidized porous silicon},
journal = {PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE},
year = {2007},
volume = {204},
number = {5},
pages = {1502-1506},
note = {5th International Conference on Porous Semiconductors - Science and Technology, Sitges, SPAIN, MAR 12-17, 2006},
doi = {{10.1002/pssa.200674403}}
}
|
| Oton, C., Lorenzo, E., Capuj, N., Lahoz, F., Martin, I., Navarro-Urrios, D., Ghulinyan, M., Sbrana, F., Gaburro, Z. & Pavesi, L. ({2005}), "Porous silicon-based Notch filters and waveguides" , In Photonic Materials, Devices, and Applications, Pts 1 and 2. Vol. {5840} ({Part 1-2}) , pp. {434-443}. Note:Conference on Photonic Materials, Devices and Applications, Seville, SPAIN, MAY 09-11, 2005. |
| Abstract: We present an experimental work on porous silicon-based optical devices. Notch filters and planar waveguides are fabricated and characterized. Three different types of filters are shown, the first one is a stop-band filter in the 1.5 mu m region, where improvements have been performed (smoothing of the index profile, apodization and index-matching). The second is a double Notch filter in the IR range, which blocks two different frequencies. Finally Notch filters in the visible range are shown, where porous silicon has been completely oxidized. Double layer waveguides are fabricated and characterized by atomic force microscopy, luminescence and prism coupling techniques. All the results shown are compared with numerical calculations. The photoluminescence changes and the refractive index variations for different annealing times are modeled in terms of oxidation of silicon and slow condensation of the porous structure. |
BibTeX:
@inproceedings{ISI:000231724200048,
author = {Oton, CJ and Lorenzo, E and Capuj, N and Lahoz, F and Martin, IR and Navarro-Urrios, D and Ghulinyan, M and Sbrana, F and Gaburro, Z and Pavesi, L},
title = {Porous silicon-based Notch filters and waveguides},
booktitle = {Photonic Materials, Devices, and Applications, Pts 1 and 2},
year = {2005},
volume = {5840},
number = {Part 1-2},
pages = {434-443},
note = {Conference on Photonic Materials, Devices and Applications, Seville, SPAIN, MAY 09-11, 2005},
doi = {{10.1117/12.608231}}
}
|
| Oton, C.J., Navarro-Urrios, D., Capuj, N.E., Ghulinyan, M., Pavesi, L., Gonzalez-Perez, S., Lahoz, F. & Martin, I.R. ({2006}), "Optical gain in dye-impregnated oxidized porous silicon waveguides" , APPLIED PHYSICS LETTERS. , JUL 3, {2006}. Vol. {89} ({1}) |
| Abstract: Positive optical gain under pulsed excitation in oxidized porous silicon planar waveguides impregnated with Nile blue (LC 6900) is reported. Amplified spontaneous emission measurements show a dramatic line narrowing when the pump energy is increased, together with a strong superlinear behavior. Variable stripe length measurements were performed to characterize quantitatively the amplification, and an unambiguous transition from losses to gain is observed with a threshold of similar to 3 mJ/cm(2) at 700 nm. A maximum gain coefficient of 8.7 cm(-1) (similar to 40 dB/cm) is reported. Shifting excitation spot measurements confirm the reliability of our results. This system is interesting in view of an optically pumped silicon-based pulsed laser. (c) 2006 American Institute of Physics. |
BibTeX:
@article{ISI:000238849200007,
author = {Oton, C. J. and Navarro-Urrios, D. and Capuj, N. E. and Ghulinyan, M. and Pavesi, L. and Gonzalez-Perez, S. and Lahoz, F. and Martin, I. R.},
title = {Optical gain in dye-impregnated oxidized porous silicon waveguides},
journal = {APPLIED PHYSICS LETTERS},
year = {2006},
volume = {89},
number = {1},
doi = {{10.1063/1.2219121}}
}
|
| Palao, J.P., Kosloff, R. & Koch, C.P. ({2008}), "Protecting coherence in optimal control theory: State-dependent constraint approach" , PHYSICAL REVIEW A. , JUN, {2008}. Vol. {77} ({6}) |
| Abstract: Optimal control theory is developed for the task of obtaining an objective in a subspace of the Hilbert space while avoiding population transfer to other subspaces. The objective, a state-to-state transition or a unitary transformation, is carried out without loss of coherence, provided the system in the allowed subspace is decoupled from its environment. An optimization functional is introduced that leads to monotonic convergence of the algorithm. This approach becomes necessary for molecular systems which are subject to processes implying loss of coherence such as ionization or predissociation. In the subspaces corresponding to lossy channels, controllability is hampered or even completely lost. A functional constraint that depends on the state of the system at each instant in time keeps the system out of the lossy channels. We outline the resulting algorithm and discuss its convergence properties. The functionality of the algorithm is demonstrated for the examples of a state-to-state transition and of a unitary transformation for a model of cold Rb-2. |
BibTeX:
@article{ISI:000257288800122,
author = {Palao, Jose P. and Kosloff, Ronnie and Koch, Christiane P.},
title = {Protecting coherence in optimal control theory: State-dependent constraint approach},
journal = {PHYSICAL REVIEW A},
year = {2008},
volume = {77},
number = {6},
doi = {{10.1103/PhysRevA.77.063412}}
}
|
| Palmero, I.C., Gonzalez-Silgo, C., Torres, M.E., Marrero-Lopez, D., Rivera-Lopez, F., Haro-Gonzalez, P. & Solans, X. ({2008}), "Effects of Er3+ and Yb3+ doping on structural and non-linear optical properties of LiNaSO4" , JOURNAL OF LUMINESCENCE. , MAY-JUN, {2008}. Vol. {128} ({5-6}) , pp. {1025-1028}. Note:16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007. |
| Abstract: We have characterized LiNaSO4 crystals doped with rare earth (RE) (Er3+ and Yb3+) to give new insights about their structural properties relations. The samples were analyzed by X-ray single crystal diffraction and differential thermal analysis. The non-centrosymmetry was confirmed second-harmonic generation. Inductively coupled plasma (ICP) and emission experiments confirmed the nominal concentrations of the REs. Crystallographic data and two empirical models were employed to understand the structural modifications by substitution of the Na site which reduces, monotonically, the non-linear optical coefficients and the temperature of the phase transition in these crystals. (C) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000255423400100,
author = {Palmero, I. C. and Gonzalez-Silgo, C. and Torres, M. E. and Marrero-Lopez, D. and Rivera-Lopez, Fernando and Haro-Gonzalez, P. and Solans, X.},
title = {Effects of Er3+ and Yb3+ doping on structural and non-linear optical properties of LiNaSO4},
journal = {JOURNAL OF LUMINESCENCE},
year = {2008},
volume = {128},
number = {5-6},
pages = {1025-1028},
note = {16th International Conference on Dynamical Processes in Excited States of Solids, Segovia, SPAIN, JUN 17-22, 2007},
doi = {{10.1016/j.jlumin.2007.11.044}}
}
|
| Panchal, V., Manjon, F.J., Errandonea, D., Rodriguez-Hernandez, P., Lopez-Solano, J., Munoz, A., Achary, S.N. & Tyagi, A.K. ({2011}), "High-pressure study of ScVO4 by Raman scattering and ab initio calculations" , PHYSICAL REVIEW B. , FEB 25, {2011}. Vol. {83} ({6}) |
| Abstract: We report results of experimental and theoretical lattice-dynamics studies on scandium orthovanadate up to 35 GPa. Raman-active modes of the low-pressure zircon phase are measured up to 8.2 GPa, where the onset of an irreversible zircon-to-scheelite phase transition is detected. Raman-active modes in the scheelite structure are observed up to 16.5 GPa. Beyond 18.2 GPa we detected a gradual splitting of the E-g modes of the scheelite phase, indicating the onset of a second phase transition. Raman symmetries, frequencies, and pressure coefficients in the three phases of ScVO4 are discussed in the light of ab initio lattice-dynamics calculations that support the experimental results. The results on all the three phases of ScVO4 are compared with those previously reported for related orthovanadates. |
BibTeX:
@article{ISI:000287729000002,
author = {Panchal, V. and Manjon, F. J. and Errandonea, D. and Rodriguez-Hernandez, P. and Lopez-Solano, J. and Munoz, A. and Achary, S. N. and Tyagi, A. K.},
title = {High-pressure study of ScVO4 by Raman scattering and ab initio calculations},
journal = {PHYSICAL REVIEW B},
year = {2011},
volume = {83},
number = {6},
doi = {{10.1103/PhysRevB.83.064111}}
}
|
| Pardo, E., Bernot, K., Lloret, F., Julve, M., Ruiz-Garcia, R., Pasan, J., Ruiz-Perez, C., Cangussu, D., Costa, V., Lescouezec, R. & Journaux, Y. ({2007}), "Solid-state anion-guest encapsulation by metallosupramolecular capsules made from two tetranuclear copper(II) complexes" , EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. , OCT, {2007}. ({29}) , pp. {4569-4573}. |
| Abstract: A new cationic tetranuclear copper(II) complex self-assembles from one 1,3-phenylenebis(oxamato) (mpba) bridging ligand and four Cu-II ions partially blocked with N,N,N',N'-tetramethylethylenediamine (tmen) terminal ligands. In the solid state, two of these tetracopper(II) oxamato complexes of bowl-like shape and helical conformation then serve as a building block for the generation of either hetero(MP) or homochiral (MM/PP) dimeric capsules depending on the nature of the encapsulated anion guest, perchlorate or hexafluorophosphate. The overall magnetic behaviour of these metallosupramolecular capsules does not depend on the nature of the encapsulated anion guest, but it is consistent with the dimer-of-dimer structure of the tetracopper(II) cation host, where the interdimer magnetic coupling through the meta-phenylenediamidate bridge is negligibly small relative to the reasonably strong intradimer one across the oxamato bridge. |
BibTeX:
@article{ISI:000250367500002,
author = {Pardo, Emilio and Bernot, Kevin and Lloret, Francesc and Julve, Miguel and Ruiz-Garcia, Rafael and Pasan, Jorge and Ruiz-Perez, Catalina and Cangussu, Danielle and Costa, Valeria and Lescouezec, Rodrigue and Journaux, Yves},
title = {Solid-state anion-guest encapsulation by metallosupramolecular capsules made from two tetranuclear copper(II) complexes},
journal = {EUROPEAN JOURNAL OF INORGANIC CHEMISTRY},
year = {2007},
number = {29},
pages = {4569-4573},
doi = {{10.1002/ejic.200700794}}
}
|
| Pardo, E., Bernot, K., Lloret, F., Julve, M., Ruiz-Garcia, R., Pasan, J., Ruiz-Perez, C., Cangussu, D., Costa, V., Lescouezec, R. & Journauxe, Y. ({2008}), "Solid-state anion-guest encapsulation by metallosupramolecular capsules made from two tetranuclear copper(II) complexes (pg 4569, 2007)" , EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. , FEB, {2008}. ({5}) , pp. {814}. |
BibTeX:
@article{ISI:000254593800020,
author = {Pardo, Emilio and Bernot, Kevin and Lloret, Francesc and Julve, Miguel and Ruiz-Garcia, Rafael and Pasan, Jorge and Ruiz-Perez, Catalina and Cangussu, Danielle and Costa, Valeria and Lescouezec, Rodrigue and Journauxe, Yves},
title = {Solid-state anion-guest encapsulation by metallosupramolecular capsules made from two tetranuclear copper(II) complexes (pg 4569, 2007)},
journal = {EUROPEAN JOURNAL OF INORGANIC CHEMISTRY},
year = {2008},
number = {5},
pages = {814},
doi = {{10.1002/ejic.200701355}}
}
|
| Pardo, E., Cangussu, D., Lescouezec, R., Journaux, Y., Pasan, J., Delgado, F.S., Ruiz-Perez, C., Ruiz-Garcia, R., Cano, J., Julve, M. & Lloret, F. ({2009}), "Molecular-Programmed Self-Assembly of Homo- and Heterometallic Tetranuclear Coordination Compounds: Synthesis, Crystal Structures, and Magnetic Properties of Rack-Type (Cu2M2II)-M-II Complexes (M = Cu and Ni) with Tetranucleating Phenylenedioxamato Bridging Ligands" , INORGANIC CHEMISTRY. , JUN 1, {2009}. Vol. {48} ({11}) , pp. {4661-4673}. |
| Abstract: New homo- and heterobimetallic tetranuclear complexes of formula [Cu-4(mpba)(Me(4)en)(4)(H2O)(4)](ClO4)(4)center dot 3H(2)O (1), [Cu-4(mpba)(Me(4)en)(4)(H2O)(4)](PF6)(4)center dot 2H(2)O (2), [Cu-4(ppba)(Me(4)en)(4)(H2O)(4)](ClO4)(4)center dot 2H(2)O (3), [Cu-4(mpba)(dipn)(4)](ClO4)(4)center dot 3H(2)O (4), [Cu-4(ppba)(dipn)(4)](ClO4)(4)center dot 2H(2)O (5), and [Cu2Ni2(ppba)(dipn)(4)(H2O)(2)](PF6)(4) (6) [mpba= N,N'-1,3-phenylenebis(oxamate), ppba = N,N'-1,4-phenylenebis(oxamate), Me(4)en = N,N,N',N'-tetramethylethylenediamine, and dipn = dipropylenetriamine] have been synthesized and structurally and magnetically characterized. Complexes 1-6 have been prepared following a molecular-programmed self-assembly method, where a heteropolytopic tetranucleating phenylenedioxamato bridging ligand (L = mpba or ppba) is bound to four metal ions of identical or different natures (M = Cu-II and/or Ni-II) with partially blocked coordination sites by bi- or tridentate polyamine terminal ligands (L' = Me(4)en or dipn). The structures of 1-6 consist of cationic tetranuclear (Cu2M2II)-M-II entities with an overall R-4 rack-type architecture, which is made up of two oxamato-bridged homo-(1-5) or heterodinuclear (6) (CuMII)-M-II units (M = Cu and Ni) connected through either a meta- (1, 2, and 4) or a para-substituted (3, 5, and 6) phenylene spacer between the Cu-II ions. The magnetic properties of 1-6 have been interpreted according to their ``dimer-of-dimers'' structure [H = -J(S-1 center dot S-2 + S-3 center dot S-4) - J'(S-1 center dot S-3) with S-1 = S-3 = S-Cu = 1/2 and S-2 = S-4 = S-M =1/2 (M = Cu) or 1 (M = Ni)]. The homometallic Cu-4(II) complexes exhibit either strong (-J = 330-350 cm(-1)) or weak-to-moderate (-J = 4.8-87.1 cm(-1)) antiferromagnetic intradimer couplings through the oxamato bridge, depending on the bi- (1-3) or tridentate (4 and 5) nature of the terminal ligand, respectively. The heterometallic (Cu2Ni2II)-Ni-II complex with a tridentate terminal ligand (6) shows instead a moderate antiferromagnetic intradimer coupling (-J= 50 cm(-1)). Otherwise, the nature and magnitude of the interdimer coupling cannot be unambiguously determined except for the pair of homo- and heterometallic (Cu2M2II)-M-II complexes [M = Cu (5) and Ni (6)] with the p-phenylenedioxamato bridging ligand and a tridentate terminal ligand, which show a weak antiferromagnetic interdimer coupling (-J' =14 and 23 cm(-1)) across the para-substituted phenylene spacer. |
BibTeX:
@article{ISI:000266428100024,
author = {Pardo, Emilio and Cangussu, Danielle and Lescouezec, Rodrigue and Journaux, Yves and Pasan, Jorge and Delgado, Fernando S. and Ruiz-Perez, Catalina and Ruiz-Garcia, Rafael and Cano, Joan and Julve, Miguel and Lloret, Francesc},
title = {Molecular-Programmed Self-Assembly of Homo- and Heterometallic Tetranuclear Coordination Compounds: Synthesis, Crystal Structures, and Magnetic Properties of Rack-Type (Cu2M2II)-M-II Complexes (M = Cu and Ni) with Tetranucleating Phenylenedioxamato Bridging Ligands},
journal = {INORGANIC CHEMISTRY},
year = {2009},
volume = {48},
number = {11},
pages = {4661-4673},
doi = {{10.1021/ic900055d}}
}
|
| Pardo, E., Dul, M.-C., Lescouezec, R., Chamoreau, L.-M., Journaux, Y., Pasan, J., Ruiz-Perez, C., Julve, M., Lloret, F., Ruiz-Garcia, R. & Cano, J. ({2010}), "Variation of the ground spin state in homo- and hetero-octanuclear copper(II) and nickel(II) double-star complexes with a meso-helicate-type metallacryptand core" , DALTON TRANSACTIONS. Vol. {39} ({20}) , pp. {4786-4801}. |
| Abstract: Homo-and heterometallic octanuclear complexes of formula Na-2[Cu-2(mpba)(3)][Cu(Me(5)dien)](6)(ClO4)(6) center dot 12H(2)O (1), Na-2[Cu2(Mempba)(3)][Cu(Me5dien)](6)(ClO4)(6) center dot 12H(2)O (2), Na-2[Ni-2(mpba)(3)][ Cu(Me(5)dien)](6)(ClO4)(6) center dot 12H(2)O (3), Na-2[Ni-2(Mempba)(3)][Cu(Me(5)dien)](6)(ClO4)(6) center dot 9H(2)O (4), [Ni-2(mpba)(3)][Ni(dipn)(H2O)](6)(ClO4)(4) center dot 12.5H(2)O (5), and [Ni-2(Mempba) 3][Ni(dipn)( H2O)](6)(ClO4)(4) center dot 12H(2)O (6) [mpba = 1,3-phenylenebis(oxamate), Mempba = 4-methyl-1, 3-phenylenebis(oxamate), Me5dien = N, N, N', N `', N `'-pentamethyldiethylenetriamine, and dipn = dipropylenetriamine] have been synthesized through the ``complex-as-ligand/complex-as-metal'' strategy. Single-crystal X-ray diffraction analyses of 1, 3, and 5 show cationic (M2M)-M-II'(II)(6) 6 entities (M, M' = Cu and Ni) with an overall double-star architecture, which is made up of two oxamato-bridged (MM)-M-II'(II)(3) star units connected through three meta-phenylenediamidate bridges between the two central metal atoms leading to a binuclear metallacryptand core of the meso-helicate-type. Dc magnetic susceptibility data for 1-6 in the temperature range 2-300 K have been analyzed through a ``dimer-of-tetramers'' model [H = - J(S-1A center dot S-3A + S-1A center dot S-4A + S-1A center dot S-5A + S-2B center dot S-6B + S-2B center dot S-7B + S-2B center dot S-8B) -J'S-1A center dot S-2B, with S-1A = S-2B = S-M and S-3A = S-4A = S-5A = S-6B = S-7B = S-8B = S-M']. The moderate to strong antiferromagnetic coupling between the M-II and M'(II) ions through the oxamate bridge in 1-6 (-J(Cu-Cu) = 52.0-57.0 cm(-1), -J(Ni-Cu) = 39.1-44.7 cm(-1), and -J(Ni-Ni) = 26.3-26.6 cm(-1)) leads to a non-compensation of the ground spin state for the tetranuclear (MM)-M-II'(II) 3 star units [S-A = S-B = 3S(M') - S-M = 1 (1 and 2), 1/2 (3 and 4), and 2 (5 and 6)]. Within the binuclear M-2(II) meso-helicate cores of 1-4, a moderate to weak antiferromagnetic coupling between the MII ions (-J'(Cu-Cu) = 28.0-48.0 cm(-1) and -J'(Ni-Ni) = 0.16-0.97 cm(-1)) is mediated by the triple m-phenylenediamidate bridge to give a ground spin singlet (S = S-A - S-B = 0) state for the octanuclear (M2Cu6II)-Cu-II molecule. Instead, a weak ferromagnetic coupling between the Ni-II ions (J'(Ni-Ni) = 2.07-3.06 cm(-1)) operates in the binuclear NiII 2 meso-helicate core of 5 and 6 leading thus to a ground spin nonet (S = SA + SB = 4) state for the octanuclear NiII 8 molecule. Dc magnetization data for 5 reveal a small but non-negligible axial magnetic anisotropy (D = -0. 23 cm(-1)) of the S = 4 NiII 8 ground state with n estimated value of the energy barrier for magnetization reversal of 3.7 cm(-1) (U = -DS2). Ac magnetic susceptibility data for 5 show an unusual slow magnetic relaxation behaviour at low temperatures which is typical of ``cluster glasses''. The temperature dependence of the relaxation time for 5 has been interpreted on the basis of the Vogel-Fulcher law for weakly interacting clusters, with values of 2.5 K, 1.4 x 10(-6) s, and 4.0 cm(-1) for the intermolecular interaction parameter (T-0), the pre-exponential factor (tau(0)), and the effective energy barrier (U-eff), respectively. |
BibTeX:
@article{ISI:000277689800019,
author = {Pardo, Emilio and Dul, Marie-Claire and Lescouezec, Rodrigue and Chamoreau, Lise-Marie and Journaux, Yves and Pasan, Jorge and Ruiz-Perez, Catalina and Julve, Miguel and Lloret, Francesc and Ruiz-Garcia, Rafael and Cano, Joan},
title = {Variation of the ground spin state in homo- and hetero-octanuclear copper(II) and nickel(II) double-star complexes with a meso-helicate-type metallacryptand core},
journal = {DALTON TRANSACTIONS},
year = {2010},
volume = {39},
number = {20},
pages = {4786-4801},
doi = {{10.1039/b926709c}}
}
|
| Pardo, E., Ferrando-Soria, J., Dul, M.-C., Lescouezec, R., Journaux, Y., Ruiz-Garcia, R., Cano, J., Julve, M., Lloret, F., Canadillas-Delgado, L., Pasan, J. & Ruiz-Perez, C. ({2010}), "Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable Ferromagnetic Metal-Organic Wires" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {16} ({43}) , pp. {12838-12851}. |
| Abstract: Double-stranded copper(II) string complexes of varying nuclearity, from di- to tetranuclear species, have been prepared by the Cu-II-mediated self-assembly of a novel family of linear homo- and heteropolytopic ligands that contain two outer oxamato and either zero (1b), one (2b), or two (3b) inner oxamidato donor groups separated by rigid 2-methyl-1,3-phenylene spacers. The X-ray crystal structures of these Cu-n(II) complexes (n = 2 (1d), 3 (2d), and 4 (3d)) show a linear array of metal atoms with an overall twisted coordination geometry for both the outer CuN2O2 and inner CuN4 chromophores. Two such nonplanar all-syn bridging ligands 1b-3b in an anti arrangement clamp around the metal centers with alternating M and P helical chiralities to afford an overall double meso-helicate-type architecture for 1d-3d. Variable-temperature (2.0-300 K) magnetic susceptibility and variable-field (0-5.0 T) magnetization measurements for 1d-3d show the occurrence of S = nS(Cu) (n = 2-4) high-spin ground states that arise from the moderate ferromagnetic coupling between the unpaired electrons of the linearly disposed Cu-II ions (S-Cu = 1 = 2) through the two anti m-phenylenediamidate-type bridges (J values in the range of + 15.0 to 16.8 cm(-1)). Density functional theory (DFT) calculations for 1d-3d evidence a sign alternation of the spin density in the meta-substituted phenylene spacers in agreement with a spin polarization exchange mechanism along the linear metal array with overall intermetallic distances between terminal metal centers in the range of 0.7-2.2 nm. Cyclic voltammetry (CV) and rotating-disk electrode (RDE) electrochemical measurements for 1d-3d show several reversible or quasireversible one-or two-electron steps that involve the consecutive metal-centered oxidation of the inner and outer Cu-II ions (S-Cu = 1 = 2) to diamagnetic Cu-III ones (S-Cu = 0) at relatively low formal potentials (E values in the range of +0.14 to 0.25 V and of +0.43 to 0.67 V vs. SCE, respectively). Further developments may be envisaged for this family of oligo-m-phenyleneoxalamide copper(II) double mesocates as electro-switchable ferromagnetic `metal-organic wires' (MOWs) on the basis of their unique ferromagnetic and multicenter redox behaviors. |
BibTeX:
@article{ISI:000284063900012,
author = {Pardo, Emilio and Ferrando-Soria, Jesus and Dul, Marie-Claire and Lescouezec, Rodrigue and Journaux, Yves and Ruiz-Garcia, Rafael and Cano, Joan and Julve, Miguel and Lloret, Francesc and Canadillas-Delgado, Laura and Pasan, Jorge and Ruiz-Perez, Catalina},
title = {Oligo-m-phenyleneoxalamide Copper(II) Mesocates as Electro-Switchable Ferromagnetic Metal-Organic Wires},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2010},
volume = {16},
number = {43},
pages = {12838-12851},
doi = {{10.1002/chem.201001737}}
}
|
| Pardo, E., Ruiz-Garcia, R., Lloret, F., Faus, J., Julve, M., Journaux, Y., Novak, M.A., Delgado, F.S. & Ruiz-Perez, C. ({2007}), "Ligand design for heterobimetallic single-chain magnets: Synthesis, crystal structures, and magnetic properties of (MCUII)-C-II (M=Mn, Co) chains with sterically hindered methyl-substituted phenyloxamate bridging ligands" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {13} ({7}) , pp. {2054-2066}. |
| Abstract: Two new series of neutral oxamato-bridged heterobimetallic chains of general formula [MCu(L-x)(2)]. mDMSO (m=0-4) (L-1=N-2-methyl-phenyloxamate, M=Mn (1a) and Co (1b); L-2 = N-2,6-dimethylphenyloxamate, M=Mn (2a) and Co (2b); L-3= N-2,4,6-trimethylphenyloxamate, M = Mn (3a) and Co (3b)) have been prepared by reaction between the corresponding anionic oxamatocopper(II) complexes [Cu(L-x)(2)](2-) with Mn2+ or Co2+ cations in DMSO. The crystal structures of [CoCu(L-2)(2)(H2O)(2)] (2b') and [CoCu(L-3)(2)(H2O)(2)](.)4H(2)O (3b') have been solved by single-crystal X-ray diffraction methods. Compounds 2b' and 3b' adopt zigzag and linear chain structures, respectively. The intrachain (CuCo)-Co-... distance through the oxamate bridge is 5.296(1) angstrom in 2b' and 5.301(2) angstrom in 3B', while the shortest interchain (CoCo)-Co-... distance is 5.995(5) angstrom in 2b' and 8.702(3) angstrom in 3b', that is, the chains are well isolated in the crystal lattice due to the presence of the bulky methyl-substituted phenyl groups. Although both (MnCuII)-Cu-II and (CoCuII)-Cu-II chains exhibit ferrimagnetic behaviour with moderately strong intrachain antiferromagnetic coupling (-J(Mn.Cu) =24.7-27.9 cm(-1) and -J(CoCu) = 35.0-45.8 cm(-1); H= Sigma - J(M.Cu)S(M,i)S(Cu.i)), only the (CoCuII)-Cu-II chains show slow magnetic relaxation at low temperatures (T-B < 3.5 K), which is characteristic of single-chain magnets (SCMs) because of the high magnetic anisotropy of the Coll ion. The blocking temperatures Tu along this series of chains vary according to the steric hindrance of the aromatic substituent of the oxamate ligand in the series L-1 < L-2 < L-3. Analysis of the SCM behaviour for 3b and 3b' on the basis of Glauber's theory for a one-dimensional Ising system showed a thermally activated mechanism for the magnetic relaxation (Arrhenius law dependence). The activation energies Ea to reverse the magnetisation direction are 38.0 (3b) and 16.3cm(-1) (W), while the preexponential factors tau(0) are 2.3x10(-11) (3b) and 4.0x10(-9) s (3b'). |
BibTeX:
@article{ISI:000244914700016,
author = {Pardo, Emilio and Ruiz-Garcia, Rafael and Lloret, Francesc and Faus, Juan and Julve, Miguel and Journaux, Yves and Novak, Miguel A. and Delgado, Fernando S. and Ruiz-Perez, Catalina},
title = {Ligand design for heterobimetallic single-chain magnets: Synthesis, crystal structures, and magnetic properties of (MCUII)-C-II (M=Mn, Co) chains with sterically hindered methyl-substituted phenyloxamate bridging ligands},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2007},
volume = {13},
number = {7},
pages = {2054-2066},
doi = {{10.1002/chem.200600992}}
}
|
| Pardo, E., Ruiz-Garcia, R., Lloret, F., Julve, M., Cano, J., Pasan, J., Ruiz-Perez, C., Chamoreau, L.-M. & Journaux, Y. ({2007}), "Molecular-programmed self-assembly of homometallic and heterometallic pentanuclear and hexanuclear coordination compounds: Synthesis, crystal structures, and magnetic properties of ladder-type (Cu2MxII)-M-II (M= Cu, Ni; x=3, 4) oxamato complexes with Cu-2(II) metallacyclophane cores" , INORGANIC CHEMISTRY. , MAY 28, {2007}. Vol. {46} ({11}) , pp. {4504-4514}. |
| Abstract: New homo- and heterometallic, hexa- and pentanuclear complexes of formula [Cu-2(mpba)(2)(H2O)F][Cu(Me(5)dien)](4)(PF6)(3)center dot 5H(2)O (1), [Cu-2(Me(3)mpba)(2)(H2O)(2)][Cu(Me(5)dien)](4)(ClO4)(4)center dot 12H(2)O (2), [Cu-2(ppba)(2)][Cu(Me(5)dien)](4)(ClO4)(4) (3), and [Ni(cyclam)][Cu-2(mpba)(2)][Ni(cyclam)](3)(ClO4)(4)center dot 6H(2)O (4) [mpba = 1,3-phenylenebis(oxamate), Me(3)mpba = 2,4,6-trimethyl-1,3-phenylenebis(oxamate), ppba = 1,4-phenylenebis(oxamate), Me(5)dien = N,N,N'N' `,N' `-pentamethyldiethylenetriamine, and cyclam = 1,4,8,11-tetraazacyclotetradecane] have been synthesized through the use of the ``complex-as-ligand/complex-as-metal'' strategy. The structures of 1-3 consist of cationic Cu-6(II) entities with an overall [2 x 2] ladder-type architecture which is made up of two oxamato-bridged Cu-3(II) linear units connected through two m- or p-phenylenediamidate bridges between the two central copper atoms to give a binuclear metallacyclic core of the cyclophane-type. Complex 4 consists of cationic (Cu2Ni3II)-Ni-II entities with an incomplete [2 x 2] ladder-type architecture which is made up of oxamato-bridged (CuNiII)-Ni-II and (CuNi2II)-Ni-II linear units connected through two m-phenylenediamidate bridges between the two copper atoms to give a binuclear metallacyclophane core. The magnetic properties of 1-3 and 4 have been interpreted according to their distinct ``dimer-of-trimers'' and ``dimer-plus-trimer'' structures, respectively, (H = -J(S-1A center dot S-3A + S-1A center dot S-4A + S-2B center dot S-5B + S-2B center dot S-6B) - J'S-1A center dot S-2B). Complexes 1-4 exhibit moderate to strong antiferromagnetic coupling through the oxamate bridges (-J(Cu-Cu) = 81.3-105.9 cm(-1); -J(Cu-Ni) = 111.6 cm(-1)) in the trinuclear and/or binuclear units. Within the binuclear metallacyclophane core, a weak to moderate ferromagnetic coupling (J'(Cu-Cu) = 1.7-9.0 cm(-1)) operates through the double m-phenylenediamidate bridge, while a strong antiferromagnetic coupling (J'(Cu-Cu) = -120.6 cm(-1)) is mediated by the double p-phenylenediamidate bridge. |
BibTeX:
@article{ISI:000246581500022,
author = {Pardo, Emilio and Ruiz-Garcia, Rafael and Lloret, Francesc and Julve, Miguel and Cano, Joan and Pasan, Jorge and Ruiz-Perez, Catalina and Chamoreau, Lise-Marie and Journaux, Yves},
title = {Molecular-programmed self-assembly of homometallic and heterometallic pentanuclear and hexanuclear coordination compounds: Synthesis, crystal structures, and magnetic properties of ladder-type (Cu2MxII)-M-II (M= Cu, Ni; x=3, 4) oxamato complexes with Cu-2(II) metallacyclophane cores},
journal = {INORGANIC CHEMISTRY},
year = {2007},
volume = {46},
number = {11},
pages = {4504-4514},
doi = {{10.1021/ic062453w}}
}
|
| Pardo, E., Train, C., Lescouezec, R., Journaux, Y., Pasan, J., Ruiz-Perez, C., Delgado, F.S., Ruiz-Garcia, R., Lloret, F. & Paulsen, C. ({2010}), "Single chain magnet behaviour in an enantiopure chiral cobalt(II)-copper(II) one-dimensional compound" , CHEMICAL COMMUNICATIONS. Vol. {46} ({13}) , pp. {2322-2324}. |
| Abstract: The self-assembly of an enantiomerically pure, chiral dianionic oxamatocopper(II) complex with cobalt(II) ions leads to neutral oxamato-bridged heterobimetallic chains that combine chirality and slow magnetic relaxation, providing thus the first example of ``chiral single chain magnets'' (CSCMs). |
BibTeX:
@article{ISI:000275662100047,
author = {Pardo, Emilio and Train, Cyrille and Lescouezec, Rodrigue and Journaux, Yves and Pasan, Jorge and Ruiz-Perez, Catalina and Delgado, Fernando S. and Ruiz-Garcia, Rafael and Lloret, Francesc and Paulsen, Carley},
title = {Single chain magnet behaviour in an enantiopure chiral cobalt(II)-copper(II) one-dimensional compound},
journal = {CHEMICAL COMMUNICATIONS},
year = {2010},
volume = {46},
number = {13},
pages = {2322-2324},
doi = {{10.1039/b920231e}}
}
|
| Pasan, J., Sanchiz, J., Canadillas-Delgado, L., Fabelo, O., Deniz, M., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2009}), "Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses, structural characterization and magnetic properties" , POLYHEDRON. , JUN 22, {2009}. Vol. {28} ({9-10, Sp. Iss. SI}) , pp. {1802-1807}. Note:11th International Conference on Molecule-Based Magnets (ICMM 2008), Florence, ITALY, SEP 21-24, 2008. |
| Abstract: Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H2O)] (1) and [Cu(2,4'-bpy)(Memal)(H2O)] center dot 3H(2)O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4'-bpy = 2,4'-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2(1)/n and Z = 4, with unit cell parameters a = 8.5874(13)angstrom, b = 7.1738(14)angstrom, c = 19.093(5)angstrom, beta = 99,509(15)degrees in 1 and a = 17.375(4)angstrom, b = 7.3305(14)angstrom, c = 14.247(3)angstrom, beta = 111.409(15)degrees in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4'-bpy (2) ligands which are stacked through pi-pi interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2-290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm(-1) (1) and J = +2.62(2)cm(-1) (2)]. (C) 2009 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000267580000041,
author = {Pasan, Jorge and Sanchiz, Joaquin and Canadillas-Delgado, Laura and Fabelo, Oscar and Deniz, Mariadel and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses, structural characterization and magnetic properties},
journal = {POLYHEDRON},
year = {2009},
volume = {28},
number = {9-10, Sp. Iss. SI},
pages = {1802-1807},
note = {11th International Conference on Molecule-Based Magnets (ICMM 2008), Florence, ITALY, SEP 21-24, 2008},
doi = {{10.1016/j.poly.2008.12.011}}
}
|
| Pasan, J., Sanchiz, J., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2007}), "Crystal engineering of 3-D coordination polymers by pillaring ferromagnetic copper(II)-methylmalonate layers" , CRYSTENGCOMM. Vol. {9} ({6}) , pp. {478-487}. |
| Abstract: Three new copper(II) complexes of formula [Cu(Memal)(H2O)](n) (1), [Cu-2(pyz)(Memal)(2)] (2) and [Cu-2(4,4'-bpy)(Memal)(2)(H2O)(2)] (3) (Memal = methylmalonate, pyz = pyrazine and 4,4'-bpy = 4,4'-bipyridine) were obtained and structurally characterized by X-ray diffraction. Complex 1 is a square grid of aquacopper(II) units which are linked by carboxylate-methylmalonate groups in the anti-syn (equatorial-equatorial) coordination mode. The crystal structures of 2 and 3 consist of corrugated layers of copper(II) (2) and aquacopper(II) (3) units with intralayer carboxylate-methylmalonate bridges in the anti-syn (equatorial-apical) coordination mode which are linked through pyrazine (2) and 4,4'-bipyridine (3) ligands; to build up a 3-D network. Magnetic susceptibility measurements of complexes 1-3 in the temperature range 2-300 K show the occurrence of an overall ferromagnetic behaviour with a weak intralayer ferromagnetic coupling (J = +1.61(1) cm(-1)) in 1 whereas two opposite magnetic interactions occur in 2 and 3, one ferromagnetic through the anti-syn carboxylate (2 and 3) and the other antiferromagnetic through pyz (2) and 4,49-bpy) (3). |
BibTeX:
@article{ISI:000247104000019,
author = {Pasan, Jorge and Sanchiz, Joaquin and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {Crystal engineering of 3-D coordination polymers by pillaring ferromagnetic copper(II)-methylmalonate layers},
journal = {CRYSTENGCOMM},
year = {2007},
volume = {9},
number = {6},
pages = {478-487},
doi = {{10.1039/b701788j}}
}
|
| Pasan, J., Sanchiz, J., Ruiz-Perez, C., Campo, J., Lloret, F. & Julve, M. ({2006}), "Metamagnetism in hydrophobically induced carboxylate (phenylmalonate)-bridged copper(II) layers" , CHEMICAL COMMUNICATIONS. ({27}) , pp. {2857-2859}. |
| Abstract: Self-assembly of copper(II) ions, phenylmalonate and pyrimidine yields the layered compound [Cu(pym)(Phmal)](n) ( 1) where intralayer ferro- and interlayer antiferromagnetic interactions occur with three-dimensional antiferromagnetic ordering at T-c = 2.15 K. |
BibTeX:
@article{ISI:000239251200006,
author = {Pasan, Jorge and Sanchiz, Jaquin and Ruiz-Perez, Catalina and Campo, Javier and Lloret, Francesc and Julve, Miguel},
title = {Metamagnetism in hydrophobically induced carboxylate (phenylmalonate)-bridged copper(II) layers},
journal = {CHEMICAL COMMUNICATIONS},
year = {2006},
number = {27},
pages = {2857-2859},
doi = {{10.1039/b602144a}}
}
|
| Pasan, J., Sanchiz, J., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2005}), "Polymeric networks of copper(II) phenylmalonate with heteroaromatic N-donor ligands: Synthesis, crystal structure, and magnetic properties" , INORGANIC CHEMISTRY. , OCT 31, {2005}. Vol. {44} ({22}) , pp. {7794-7801}. |
| Abstract: Two new phenylmalonate-bridged copper(II) complexes with the formulas [Cu(4,4'-bpy)(Phmal)]center dot 2nH(2)O (1) and [Cu(2,4'-bpy)(Phmal)(H2O](n) (2) (Phmal = phenylmalonate dianion, 4,4'-bpy = 4,4'-bipyridine, 2,4'-bpy = 2,4'-bipyridine) have been synthesized and characterized by X-ray diffraction. Complex 1 crystallizes in monoclinic space group P2(1), Z = 4, with unit cell parameters of a = 9.0837(6) angstrom, b = 9.3514(4) angstrom, c = 11.0831(8) angstrom, and beta = 107.807(6)degrees, whereas complex 2 crystallizes in orthorhombic space group C2cb, Z = 8, with unit cell parameters of a = 10.1579(7) angstrom, b = 10.3640(8) angstrom, and c = 33.313(4) angstrom. The structures of 1 and 2 consist of layers of copper(II) ions with bridging bis-monodentate phenylmalonate (1 and 2) and 4,4'-bpy (1) ligands and terminal monodentate 2,4'-bpy (2) groups. Each layer in 1 contains rectangles with dimensions of 11.08 x 4.99 angstrom(2), the edges being defined by the Phmal and 4,4'-bpy ligands. The intralayer copper-copper separations in 1 through the anti-syn equatorial-apical carboxylate-bridge and the 4,4'-bpy molecule are 4.9922(4) and 11.083(1) angstrom, respectively. The anti-syn equatorial-equatorial carboxylate bridge links the copper(II) atoms in complex 2 within each layer with a mean copper-copper separation of 5.3709(8) angstrom. The presence of 2,4'-bpy as a terminal ligand accounts for the large interlayer separation of 15.22 angstrom. The copper(H) environment presents a static pseudo-Jahn-Teller disorder which has been studied by EPR and low-temperature X-ray diffraction. Magnetic susceptibility measurements of both compounds in the temperature range 2-290 K show the occurrence of weak antiferromagnetic [J = -0.59(1) cm(-1) (1)] and ferromagnetic [J = +0.77(1) cm(-1) (2)] interactions between the copper(II) ions. The conformation of the phenylmalonate-carboxylate bridge and other structural factors, such as the planarity of the exchange pathway in 1, account for the different nature of the magnetic interaction. |
BibTeX:
@article{ISI:000232898800017,
author = {Pasan, J and Sanchiz, J and Ruiz-Perez, C and Lloret, F and Julve, M},
title = {Polymeric networks of copper(II) phenylmalonate with heteroaromatic N-donor ligands: Synthesis, crystal structure, and magnetic properties},
journal = {INORGANIC CHEMISTRY},
year = {2005},
volume = {44},
number = {22},
pages = {7794-7801},
doi = {{10.1021/ic0503986}}
}
|
| Pasan, J., Sanchiz, J., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2004}), "Phenylmalonate-containing copper(II) complexes: Synthesis, crystal structure and magnetic properties" , EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. , OCT 18, {2004}. ({20}) , pp. {4081-4090}. |
| Abstract: Three new copper(II) complexes of formula [Cu(2,2'-bpy)(Phmal)(H2O).2H(2)O (1), [Cu(2,2'-bpym)(Phmal)](n) (2) and [Cu(phen)(Phmal)](n).3nH(2)O (3) (Phmal = phenylmalonate- 2,2'-bpy = 2,2'-bipyridine; 2,2'-bpym = 2,2'-bipyrimidine; phen = 1,10-phenanthroline) have been prepared and their structures determined by X-ray diffraction techniques. Complex 1 is mononuclear whereas 2 and 3 are uniform chain compounds. The copper atoms in 1-3 are distorted square-pyramidal: two nitrogen atoms from the bidentate nitrogen heterocycle and two carboxylate oxygen atoms from the phenylmalonate ligand build the equatorial plane; the axial position is filled either by a water molecule (1) or a carboxylate oxygen atom from another pheny1malonate group (2 and 3). The values of the intrachain copper-copper separation through the phenylmalonate-carboxylate bridge in the |
BibTeX:
@article{ISI:000225781600016,
author = {Pasan, J and Sanchiz, J and Ruiz-Perez, C and Lloret, F and Julve, M},
title = {Phenylmalonate-containing copper(II) complexes: Synthesis, crystal structure and magnetic properties},
journal = {EUROPEAN JOURNAL OF INORGANIC CHEMISTRY},
year = {2004},
number = {20},
pages = {4081-4090},
doi = {{10.1002/ejic.200400260}}
}
|
| Pellicer-Porres, J., Martinez-Garcia, D., Segura, A., Rodriguez-Hernandez, P., Munoz, A., Chervin, J.C., Garro, N. & Kim, D. ({2006}), "Pressure and temperature dependence of the lattice dynamics of CuAlO2 investigated by Raman scattering experiments and ab initio calculations" , PHYSICAL REVIEW B. , NOV, {2006}. Vol. {74} ({18}) |
| Abstract: We have studied the vibrational properties of CuAlO2 by means of Raman scattering in ambient conditions, at low temperature, and also at high pressure. Results are discussed in the framework of an ab initio calculation. Raman active modes have wave numbers sigma(Eg)=418.1 +/- 0.2 cm(-1) and sigma(A1g)=767.2 +/- 0.3 cm(-1). Polarized measurements with single crystals have confirmed their symmetry. We present and discuss the phonon-dispersion curves. Below 200 K, the temperature dependence of the Raman active modes is almost linear, with coefficients partial derivative sigma(Eg)/partial derivative T=(-4 +/- 1)x10(-3) cm(-1)/K and partial derivative sigma(A1g)/partial derivative T=(-1.0 +/- 0.2)x10(-2) cm(-1)/K. Most of the temperature shift is associated with thermal expansion. The pressure dependence is given by partial derivative sigma(Eg)/partial derivative P=2.72 +/- 0.07 cm(-1)/GPa and partial derivative sigma(A1g)/partial derivative P=4.96 +/- 0.12 cm(-1)/GPa. We observe a reversible phase transition at 34 +/- 2 GPa, which, as already has been shown to happen in CuGaO2, we relate to the existence of a dynamical instability. |
BibTeX:
@article{ISI:000242409100038,
author = {Pellicer-Porres, J. and Martinez-Garcia, D. and Segura, A. and Rodriguez-Hernandez, P. and Munoz, A. and Chervin, J. C. and Garro, N. and Kim, D.},
title = {Pressure and temperature dependence of the lattice dynamics of CuAlO2 investigated by Raman scattering experiments and ab initio calculations},
journal = {PHYSICAL REVIEW B},
year = {2006},
volume = {74},
number = {18},
doi = {{10.1103/PhysRevB.74.184301}}
}
|
| Pellicer-Porres, J., Segura, A., Gilliland, A., Munoz, A., Rodriguez-Hernendez, P., Kim, D., Lee, M. & Kim, T. ({2006}), "On the band gap of CuAlO2 delafossite" , APPLIED PHYSICS LETTERS. , MAY 1, {2006}. Vol. {88} ({18}) |
| Abstract: In this letter, we discuss the electronic structure of copper aluminate (CuAlO2) on the basis of absorption measurements at low temperature and under high pressure in single crystals and thin films, combined with ab initio electronic structure calculations. The indirect character of the fundamental transition could be clearly established through the photon energy dependence of the absorption edge as measured in single crystals, yielding a band gap (plus a phonon) of 2.99 +/- 0.01 eV at room temperature. An indirect excitonic structure is also observed at low temperature. The lowest energy direct allowed transition occurs near 3.53 +/- 0.01 eV and is identified through its low-energy tail in single crystals and its excitonic peak in thin films. Comparing our results with ab initio calculations available in the literature, we conclude that CuGaO2 and CuInO2 can hardly be considered as wide gap semiconductors, even if they are transparent in thin films. (c) 2006 American Institute of Physics. |
BibTeX:
@article{ISI:000237321600026,
author = {Pellicer-Porres, J and Segura, A and Gilliland, AS and Munoz, A and Rodriguez-Hernendez, P and Kim, D and Lee, MS and Kim, TY},
title = {On the band gap of CuAlO2 delafossite},
journal = {APPLIED PHYSICS LETTERS},
year = {2006},
volume = {88},
number = {18},
doi = {{10.1063/1.2200398}}
}
|
| Pellicer-Porres, J., Segura, A., Munoz, A., Polian, A. & Congeduti, A. ({2010}), "Bond length compressibility in hard ReB2 investigated by x-ray absorption under high pressure" , JOURNAL OF PHYSICS-CONDENSED MATTER. , FEB 3, {2010}. Vol. {22} ({4}) |
| Abstract: This work describes x-ray absorption measurements under high pressure in ReB2, complemented by ab initio calculations. The EXAFS analysis yields the average Re-B bond compressibility, which turns out to be chi(ReB) = 5.6(9) x 10(-4) GPa(-1). Combining this information with previous x-ray diffraction experiments we have characterized the network of covalent bonds responsible for the rigidity of the structure. The main conclusion is that the compression is anisotropic and nonhomogeneous, reflecting bonding differences between Re-B and B-B bonds and also between nonequivalent Re-B bonds. The layer defined by boron atoms tends to become flatter under high pressure. As a consequence, the structural rigidity, necessary to attain high hardness values, is compromised. |
BibTeX:
@article{ISI:000273552400019,
author = {Pellicer-Porres, J. and Segura, A. and Munoz, A. and Polian, A. and Congeduti, A.},
title = {Bond length compressibility in hard ReB2 investigated by x-ray absorption under high pressure},
journal = {JOURNAL OF PHYSICS-CONDENSED MATTER},
year = {2010},
volume = {22},
number = {4},
doi = {{10.1088/0953-8984/22/4/045701}}
}
|
| Prieto, A., Brouard, S. & Muga, J. ({2005}), "Breakdown of classical conservation of energy in a quantum wave-packet collision with a double barrier" , PHYSICAL REVIEW A. , JAN, {2005}. Vol. {71} ({1}) |
| Abstract: A transient interference during the collision of a broad quantum particle wave packet with a properly chosen potential barrier suppresses, for energies well above the barrier top, the main incident momentum. This collision enhances the momenta below and above the central one, violating the classical conservation of energy. For the double square barrier the effect is due to the interference between three components (incident, transmitted, and interbarriers terms) and survives much longer than for the single barrier, facilitating its observation. A quantum optical realization, with two-level atoms and effective laser barriers is discussed. |
BibTeX:
@article{ISI:000227283300076,
author = {Prieto, ALP and Brouard, S and Muga, JG},
title = {Breakdown of classical conservation of energy in a quantum wave-packet collision with a double barrier},
journal = {PHYSICAL REVIEW A},
year = {2005},
volume = {71},
number = {1},
doi = {{10.1103/PhysRevA.71.012703}}
}
|
| Radescu, S., Mujica, A., Lopez-Solano, J. & Needs, R.J. ({2011}), "Theoretical study of pressure-driven phase transitions in HgSe and HgTe" , PHYSICAL REVIEW B. , MAR 7, {2011}. Vol. {83} ({9}) |
| Abstract: We present the results of a density-functional-theory study of the stability of high-pressure phases of HgSe and HgTe up to the so-called Cmcm phase, which is the highest-pressure phase that has been fully characterized in experiments in these compounds. We compare the results obtained using different exchange-correlation functionals for the energetics, stability, and structure of the high-pressure phases, finding that the qualitative picture is very similar and essentially in agreement with the experimental observations. We study the cinnabar -> NaCl and the NaCl -> Cmcm transitions in detail and provide the structural evolution under pressure of the cinnabar and Cmcm phases. We find that the mechanism for the NaCl -> Cmcm transition is somewhat different from other related compounds exhibiting this transition, with cell deformation playing an important role in the stabilization of the Cmcm state in HgSe and HgTe. Our results support the view of a NaCl -> Cmcm transition that is distinctly first order, in good agreement with the experimental observations and contrary to other materials where this transition is of second order. |
BibTeX:
@article{ISI:000288070100002,
author = {Radescu, S. and Mujica, A. and Lopez-Solano, J. and Needs, R. J.},
title = {Theoretical study of pressure-driven phase transitions in HgSe and HgTe},
journal = {PHYSICAL REVIEW B},
year = {2011},
volume = {83},
number = {9},
doi = {{10.1103/PhysRevB.83.094107}}
}
|
| Radescu, S., Mujica, A. & Needs, R.J. ({2009}), "Soft-phonon instability in zincblende HgSe and HgTe under moderate pressure: Ab initio pseudopotential calculations" , PHYSICAL REVIEW B. , OCT, {2009}. Vol. {80} ({14}) |
| Abstract: The mercury chalcogenides HgSe and HgTe show peculiar behavior under moderate compression such as the unusual observation of a ``hidden'' transition from their ambient-pressure zincblende phase to an orthorhombic metastable phase with space group C222(1). We present here the results of an ab initio pseudopotential study within the framework of the density-functional theory of the stability of the low-pressure zincblende phases of HgSe and HgTe and the transition to the C222(1) structure. We relate the observation of the C222(1) phase to an instability in the transverse-acoustic phonon branches of the zincblende phases of these materials. We have studied in detail the mechanism of the zincblende -> C222(1) transition as well as the structural evolution of the C222(1) phase under pressure. |
BibTeX:
@article{ISI:000271351500046,
author = {Radescu, S. and Mujica, A. and Needs, R. J.},
title = {Soft-phonon instability in zincblende HgSe and HgTe under moderate pressure: Ab initio pseudopotential calculations},
journal = {PHYSICAL REVIEW B},
year = {2009},
volume = {80},
number = {14},
doi = {{10.1103/PhysRevB.80.144110}}
}
|
| Ramirez, M., Jaque, D., Bausa, L., Martin, I., Lahoz, F., Cavalli, E., Speghini, A. & Bettinelli, M. ({2005}), "Temperature dependence of Nd3+<-> Yb3+ energy transfer in the YAl3(BO3)(4) nonlinear laser crystal" , JOURNAL OF APPLIED PHYSICS. , MAY 1, {2005}. Vol. {97} ({9}) |
| Abstract: The temperature dependence of the Nd3+-> Yb3+ energy-transfer rate in the YAl3(BO3)(4) nonlinear laser crystal has been investigated from the analysis of fluorescence decay curves recorded in the 10-600 K range. Three different regimes, independent on the dopant concentration, have been observed in the thermal behavior of the Nd3+-> Yb3+ energy-transfer rate. By comparing experimental results with theoretical predictions based on the Dexter model [J. Chem. Phys. 21, 836 (1953)], the origin of these different regimes has been explained. In addition, the influence of temperature and of both Nd3+ and Yb3+ concentrations on the Nd3+<- Yb3+ energy back-transfer rate has been also investigated, concluding that it is a migration-assisted energy-transfer process. Finally, the populations of both Nd3+ and Yb3+ metastable states achieved after continuous-wave Nd3+ excitation have been calculated and measured and results have been explained in terms of the thermal behavior of both forward- and back-transfer rates. (C) 2005 American Institute of Physics. |
BibTeX:
@article{ISI:000229155600020,
author = {Ramirez, MO and Jaque, D and Bausa, LE and Martin, IR and Lahoz, F and Cavalli, E and Speghini, A and Bettinelli, M},
title = {Temperature dependence of Nd3+<-> Yb3+ energy transfer in the YAl3(BO3)(4) nonlinear laser crystal},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2005},
volume = {97},
number = {9},
doi = {{10.1063/1.1886887}}
}
|
| Rey, N., Munoz, A., Rodriguez-Hernandez, P. & San Miguel, A. ({2008}), "First-principles study of lithium-doped carbon clathrates under pressure" , JOURNAL OF PHYSICS-CONDENSED MATTER. , MAY 28, {2008}. Vol. {20} ({21}) |
| Abstract: We present a theoretical study of the behavior under pressure of the two hypothetical C-46 and Li8C46 type-I carbon clathrates in order to obtain new information concerning their synthesis. Using ab initio calculations, we have explored the energetic and structural properties under pressure of these two carbon based cage-like materials. These low-density metastable phases show large negative pressure transitions compared to diamond, which represent a serious obstacle to their synthesis. However, we show that a minimum energy barrier can be reached close to 40 GPa, suggesting that synthesis of the Li-clathrate under extreme conditions of pressure and temperature may be possible. The electronic band structure with related density of states behavior under pressure, as well as the dependence of the active Raman modes with pressure are also examined. |
BibTeX:
@article{ISI:000255661800018,
author = {Rey, Nicolas and Munoz, Alfonso and Rodriguez-Hernandez, Placida and San Miguel, Alfonso},
title = {First-principles study of lithium-doped carbon clathrates under pressure},
journal = {JOURNAL OF PHYSICS-CONDENSED MATTER},
year = {2008},
volume = {20},
number = {21},
doi = {{10.1088/0953-8984/20/21/215218}}
}
|
| Rivera-Lopez, F., Martin, I.R., Da Silva, I., Gonzalez-Silgo, C., Rodriguez-Mendoza, U.R., Lavin, V., Lahoz, F., Diaz-Gonzalez, S.M., Martinez-Sarrion, M.L., Mestres, L. & Fernandez-Urban, J. ({2006}), "Analysis of the Eu3+ emission in a SrWO4 laser matrix under pressure" , HIGH PRESSURE RESEARCH. , DEC, {2006}. Vol. {26} ({4}) , pp. {355-359}. Note:44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006. |
| Abstract: Optical properties of the SrWO4 matrix doped with different Eu3+ concentrations (10 13% and 20 have been studied. At ambient pressure, the temporal evolution of the emissions from the D-5(1) level has been analyzed in the different doped crystals in order to discuss the energy transfer processes between the Eu3+ ions. This study lets conclude that the Eu3+ ions are randomly distributed in the matrix. Moreover, the D-5(0) -> F-7(1,2) emissions have been measured increasing the pressure up to 15 GPa in order to analyze the changes in the Eu3+ local structure. The results confirm the existence of a structural phase transition around 8.5 GPa. |
BibTeX:
@article{ISI:000243942800011,
author = {Rivera-Lopez, Fernando and Martin, I. R. and Da Silva, I. and Gonzalez-Silgo, C. and Rodriguez-Mendoza, U. R. and Lavin, V. and Lahoz, F. and Diaz-Gonzalez, S. Maceda and Martinez-Sarrion, M. L. and Mestres, L. and Fernandez-Urban, J.},
title = {Analysis of the Eu3+ emission in a SrWO4 laser matrix under pressure},
journal = {HIGH PRESSURE RESEARCH},
year = {2006},
volume = {26},
number = {4},
pages = {355-359},
note = {44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006},
doi = {{10.1080/08957950601105085}}
}
|
| Rodriguez, V., Tikhomirov, V., Mendez-Ramos, J. & Seddon, A. ({2005}), "The shape of the 1.55 mu m emission band of the Er3+-dopant in oxyfluoride nano-scaled glass-ceramics" , EUROPHYSICS LETTERS. , JAN, {2005}. Vol. {69} ({1}) , pp. {128-134}. |
| Abstract: We propose a diagram showing the sequence of Stark-split energy levels for the I-4(15/2) and I-4(13/2) states of Er3+ doped into oxyfluoride, nano-scaled glass-ceramics based on low- and room temperature measurements of respective emission and absorption bands. The room temperature broadest and flattest 1.55 mum telecommunications emission band I-4(13/2) --> I-4(15/2) of Er3+ to date reported earlier for such glass-ceramics is interpreted using this framework. By investigating the low- temperature behaviour, we show that the shape of the 1.55 mum band at room temperature is mostly due to thermal population of higher Stark sublevels in the excited I-4(13/2) state. Two sites for Er3+ are proposed which relate, respectively, to the glassy and nano- crystalline phases of the glass-ceramics and their relative contributions to the emission spectrum are identified. The Er3+-site in the nano-crystalline phase is shown to be cubic with nearby charge compensation by one interstitial F-, without appreciable clustering of Er3+ ions. |
BibTeX:
@article{ISI:000226569300020,
author = {Rodriguez, VD and Tikhomirov, VK and Mendez-Ramos, J and Seddon, AB},
title = {The shape of the 1.55 mu m emission band of the Er3+-dopant in oxyfluoride nano-scaled glass-ceramics},
journal = {EUROPHYSICS LETTERS},
year = {2005},
volume = {69},
number = {1},
pages = {128-134},
doi = {{10.1209/epl/i2004-10314-3}}
}
|
| Rodriguez, V.D., Del Castillo, J., Yanes, A.C., Mendez-Ramos, J., Torres, M. & Peraza, J. ({2007}), "Luminescence of Er3+-doped nanostructured SiO2-LaF3 glass-ceramics prepared by the sol-gel method" , OPTICAL MATERIALS. , JUL, {2007}. Vol. {29} ({11}) , pp. {1557-1561}. |
| Abstract: Transparent glass ceramics with composition of 95SiO(2)-5LaF(3) doped with 0.1 mol% of Er3+ were synthesized by thermal treatment of precursor sol-gel glasses. Segregated LaF3 nanocrystals in the glass were confirmed from a structural analysis performed by X-ray diffraction. Blue, green and red efficient up-conversion emissions were observed under 980 nm excitation at room temperature. Under this excitation near infrared down-conversion at 1.55 mu m is also observed. These results could be attributed to the precipitation of LaF3 nanocrystals and the incorporation of most Er3+ ions in these nanocrystals. The mechanisms involved in the up-conversion emissions could be ascribed to two and three photon processes. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000247405100043,
author = {Rodriguez, V. D. and Del Castillo, J. and Yanes, A. C. and Mendez-Ramos, J. and Torres, M. and Peraza, J.},
title = {Luminescence of Er3+-doped nanostructured SiO2-LaF3 glass-ceramics prepared by the sol-gel method},
journal = {OPTICAL MATERIALS},
year = {2007},
volume = {29},
number = {11},
pages = {1557-1561},
doi = {{10.1016/j.optmat.2006.06.022}}
}
|
| Rodriguez, V.D., Tikhomirov, V.K., Mendez-Ramos, J., del Castillo, J. & Gorller-Walrand, C. ({2009}), "Measurement of Quantum Yield of Up-Conversion Luminescence in Er3+-Doped Nano-Glass-Ceramics" , JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY. , MAR, {2009}. Vol. {9} ({3}) , pp. {2072-2075}. Note:International Conference on Bionano Science (ICONBS 2007), Taipei, TAIWAN, DEC 05-07, 2007. |
| Abstract: A measurement of quantum yield of up-conversion luminescence has been done for the Er3+-doped transparent oxyfluoride glass-ceramics 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2): 3.5(ErF3) mol where most of Er3+ dopants partition in 8 nm diameter nano-crystals Er10Pb25F65. The yield was found by newly proposed method using the pump power dependence of the resonant luminescence. The result of the measurement points out that a theoretical maximum of 50% may be reached for the up-conversion luminescence yield in this material. This high yield is shown to be due to low phonon energy and short inter-dopant distances in the nano-crystals. |
BibTeX:
@article{ISI:000263653400062,
author = {Rodriguez, V. D. and Tikhomirov, V. K. and Mendez-Ramos, J. and del-Castillo, J. and Gorller-Walrand, C.},
title = {Measurement of Quantum Yield of Up-Conversion Luminescence in Er3+-Doped Nano-Glass-Ceramics},
journal = {JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY},
year = {2009},
volume = {9},
number = {3},
pages = {2072-2075},
note = {International Conference on Bionano Science (ICONBS 2007), Taipei, TAIWAN, DEC 05-07, 2007},
doi = {{10.1166/jnn.2009.411}}
}
|
| Rodriguez, V.D., Tikhomirov, V.K., Mendez-Ramos, J., Yanes, A.C. & Moshchalkov, V.V. ({2010}), "Towards broad range and highly efficient down-conversion of solar spectrum by Er3+-Yb3+ co-doped nano-structured glass-ceramics" , SOLAR ENERGY MATERIALS AND SOLAR CELLS. , OCT, {2010}. Vol. {94} ({10}) , pp. {1612-1617}. |
| Abstract: The efficiency of semiconductor solar cells could be greatly increased by down-conversion processes, which efficiently split incident solar photons into couples of photons with energy over the bandgap. Here, we show new down-conversion mechanisms in Er3+-Yb3+ co-doped glass-ceramics, where the ions are hosted by fluoride nanoparticles embedded in silica glass. By this means, 350-550 nm photons, absorbed by Er3+ ions, generate pairs of photons at the range of 650-1550 nm, emitted by Er3+ and Yb3+, with a quantum efficiency approaching the maximum of 200 (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000281074800008,
author = {Rodriguez, V. D. and Tikhomirov, V. K. and Mendez-Ramos, J. and Yanes, A. C. and Moshchalkov, V. V.},
title = {Towards broad range and highly efficient down-conversion of solar spectrum by Er3+-Yb3+ co-doped nano-structured glass-ceramics},
journal = {SOLAR ENERGY MATERIALS AND SOLAR CELLS},
year = {2010},
volume = {94},
number = {10},
pages = {1612-1617},
doi = {{10.1016/j.solmat.2010.04.081}}
}
|
| Rodriguez-Hernandez, P., Lopez-Solano, J., Radescu, S., Mujica, A., Munoz, A., Errandonea, D., Pellicer-Porres, J., Segura, A., Ferrer-Roca, C., Manjon, F.J., Kumar, R.S., Tschauner, O. & Aquilanti, G. ({2006}), "Theoretical and experimental study of CaWO4 and SrWO4 under pressure" , JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS. , SEP-OCT, {2006}. Vol. {67} ({9-10, Sp. Iss. SI}) , pp. {2164-2171}. Note:Conference on Study of Matter at Extreme Conditions (SMEC2005), Miami Beach, FL, APR 17-21, 2005. |
| Abstract: In this paper, we combine a theoretical study of the structural phases of CaWO4 and SrWO4 under high pressure along with the results of angle-dispersive X-ray diffraction (ADXRD) and X-ray absorption near-edge structure (XANES) measurements of both tungstates up to approximately 20 GPa. The theoretical study was performed within the ab initio framework of the density functional theory (DFT) using a plane-wave basis set and the pseudopotential scheme, with the generalized gradient approximation (GGA) for the exchange and correlation contribution to the energy. Under normal conditions, CaWO4 and SrWO4 crystallize in the scheelite structure. Our results show that in a hydrostatic environment, both compounds undergo a scheelite-to-fergusonite phase transition with increasing pressure. We present a comparison of the evolution of the structural parameters, equation of state, and of the features of the transition, finding an overall excellent agreement between the experimental and theoretical results. (c) 2006 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000241089600039,
author = {Rodriguez-Hernandez, P. and Lopez-Solano, J. and Radescu, S. and Mujica, A. and Munoz, A. and Errandonea, D. and Pellicer-Porres, J. and Segura, A. and Ferrer-Roca, Ch. and Manjon, F. J. and Kumar, R. S. and Tschauner, O. and Aquilanti, G.},
title = {Theoretical and experimental study of CaWO4 and SrWO4 under pressure},
journal = {JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS},
year = {2006},
volume = {67},
number = {9-10, Sp. Iss. SI},
pages = {2164-2171},
note = {Conference on Study of Matter at Extreme Conditions (SMEC2005), Miami Beach, FL, APR 17-21, 2005},
doi = {{10.1016/j.jpcs.2006.05.011}}
}
|
| Rodriguez-Hernandez, P. & Munoz, A. ({2005}), "Theoretical study of the pressure-induced structural phase transition of ScSb and YSb" , INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY. , FEB 20, {2005}. Vol. {101} ({6}) , pp. {770-773}. Note:10th International Conference on the Applications of Density Functional Theory in Chemistry and Physics, Brussels, BELGIUM, SEP 05-12, 2003. |
| Abstract: The equations of state and phase stability of ScSb and YSb were investigated via a first-principles theoretical calculation. For each compound we fixed the B1 (NaCl) structure as the ambient pressure phase and considered the B2 (CsCl) structure as a candidate for the high-pressure phases. We report the results of the structural and electronic properties of these compounds in the considered structures and the theoretical transition pressure. (C) 2004 Wiley Periodicals, Inc. |
BibTeX:
@article{ISI:000226910200017,
author = {Rodriguez-Hernandez, P and Munoz, A},
title = {Theoretical study of the pressure-induced structural phase transition of ScSb and YSb},
journal = {INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY},
year = {2005},
volume = {101},
number = {6},
pages = {770-773},
note = {10th International Conference on the Applications of Density Functional Theory in Chemistry and Physics, Brussels, BELGIUM, SEP 05-12, 2003},
doi = {{10.1002/qua.20336}}
}
|
| Rodriguez-Hernandez, P., Munoz, A., Pellicer-Porres, J., Martinez-Garcia, D., Segura, A., Garro, N., Chervin, J.C. & Kim, D. ({2007}), "Lattice dynamics of CuAlO2 under high pressure from ab initio calculations" , PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS. , JAN, {2007}. Vol. {244} ({1}) , pp. {342-346}. Note:12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006. |
| Abstract: The density functional perturbation theory is employed to study the vibrational properties of CuAlO2 under pressure. The calculations are preformed using the pseudopotential wave method and the local density approximation for the exchange-correlation (XC) potential. The d electrons of Cu are treated as valence states. We present the phonon dispersion curves. Our results are in good agreement with the available experimental Raman scattering experiments. A initio calculations show the presence of a dynamical instability, possibly related with the experimentally observed phase transition. |
BibTeX:
@article{ISI:000243693600061,
author = {Rodriguez-Hernandez, P. and Munoz, A. and Pellicer-Porres, J. and Martinez-Garcia, D. and Segura, A. and Garro, N. and Chervin, J. C. and Kim, D.},
title = {Lattice dynamics of CuAlO2 under high pressure from ab initio calculations},
journal = {PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS},
year = {2007},
volume = {244},
number = {1},
pages = {342-346},
note = {12th International Conference on High Pressure Semiconductor Physics (HPSP-12), Barcelona, SPAIN, JUL 31-AUG 03, 2006},
doi = {{10.1002/pssb.200672519}}
}
|
| Rodriguez-Mendoza, U.R., Rodenas, A., Jaque, D., Martin, I.R., Lahoz, F. & Lavin, V. ({2006}), "High-pressure luminescence in Nd3+-doped MgO : LiNbO3" , HIGH PRESSURE RESEARCH. , DEC, {2006}. Vol. {26} ({4}) , pp. {341-344}. Note:44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006. |
| Abstract: Optical properties of Nd3+-doped MgO:LiNbO3 have been intensively studied during the last years because of its potential applications as a multifunctional non-linear laser system capable, for example, of multi-frequency laser light generation. In order to exploit fully the advantages of this system, a complete knowledge of its excited state dynamics is required. The application of high-hydrostatic pressure is a powerful technique to study the influence of the changing strength of the crystal field on the spectroscopic properties of luminescent centers in crystals. We have studied the dependence of the emission bands and the lifetimes of the metastable F-4(3/2) state of Nd3+ on hydrostatic pressure. |
BibTeX:
@article{ISI:000243942800008,
author = {Rodriguez-Mendoza, U. R. and Rodenas, A. and Jaque, D. and Martin, I. R. and Lahoz, F. and Lavin, V.},
title = {High-pressure luminescence in Nd3+-doped MgO : LiNbO3},
journal = {HIGH PRESSURE RESEARCH},
year = {2006},
volume = {26},
number = {4},
pages = {341-344},
note = {44th Annual Meeting of the European-High-Pressure-Research-Group Meeting (EHPRG 44), Prague, CZECH REPUBLIC, SEP 04-08, 2006},
doi = {{10.1080/08957950601105044}}
}
|
| Romero-Aleman, M.D.M., Monzon-Mayor, M., Yanes, C., Santos, E., Soula, C. & Cochard, P. ({2007}), "Immunohistochemical characterization of oligodendrocyte precursors in the visual pathway of the lizard Gallotia galloti" , NEURON GLIA BIOLOGY. Vol. {2} ({Suppl. 1}) , pp. {S36}. |
BibTeX:
@article{ISI:000251708800105,
author = {Romero-Aleman, Maria Del Mar and Monzon-Mayor, Maximina and Yanes, Carmen and Santos, Elena and Soula, Catherine and Cochard, Philippe},
title = {Immunohistochemical characterization of oligodendrocyte precursors in the visual pathway of the lizard Gallotia galloti},
journal = {NEURON GLIA BIOLOGY},
year = {2007},
volume = {2},
number = {Suppl. 1},
pages = {S36}
}
|
| Romero-Aleman, M.M., Monzon-Mayor, M., Santos, E. & Yanes, C. ({2010}), "Expression of Neuronal Markers, Synaptic Proteins, and Glutamine Synthetase in the Control and Regenerating Lizard Visual System" , JOURNAL OF COMPARATIVE NEUROLOGY. , OCT 1, {2010}. Vol. {518} ({19}) , pp. {4067-4087}. |
| Abstract: Spontaneous regrowth of retinal ganglion cell (RGC) axons occurs after optic nerve (ON) transection in the lizard Gallotia galloti. To gain more insight into this event we performed an immunohistochemical study on selected neuron and glial markers, which proved useful for analyzing the axonal regrowth process in different regeneration models. In the control lizards, RGCs were beta-III tubulin- (Tuj1) and HuCD-positive. The vesicular glutamate transporter-1 (VGLUT1) preferentially stained RGCs and glial somata rather than synaptic layers. In contrast, SV2 and vesicular GABA/glycine transporter (VGAT) labeling was restricted to both plexiform layers. Strikingly, the strong expression of glutamine synthetase (GS) in both Muller glia processes and macroglial somata revealed a high glutamate metabolism along the visual system. Upregulation of Tuj1 and HuCD in the surviving RGCs was observed at all the timepoints studied (1, 3, 6, 9, and 12 months postlesion). The significant rise of Tuj1 in the optic nerve head and optic tract (OTr) by 1 and 6 months postlesion, respectively, suggests an increase of the beta-III tubulin transport and incorporation into newly formed axons. Persistent Tuj1(+) and SV2(+) puncta and swellings were abnormally observed in putative degenerating/dystrophic fibers. Unexpectedly, neuron-like cells of obscure significance were identified in the control and regenerating ON-OTr. We conclude that: 1) the persistent upregulation of Tuj1 and HuCD favors the long-lasting axonal regrowth process; 2) the latter succeeded despite the ectopia and dystrophy of some regrowing fibers; and 3) maintenance of the glutamate-glutamine cycle contributes to the homeostasis and plasticity of the system. J. Comp. Neurol. 518:4067-4087, 2010. (C) 2010 Wiley-Liss, Inc. |
BibTeX:
@article{ISI:000281331000010,
author = {Romero-Aleman, M. M. and Monzon-Mayor, M. and Santos, E. and Yanes, C.},
title = {Expression of Neuronal Markers, Synaptic Proteins, and Glutamine Synthetase in the Control and Regenerating Lizard Visual System},
journal = {JOURNAL OF COMPARATIVE NEUROLOGY},
year = {2010},
volume = {518},
number = {19},
pages = {4067-4087},
doi = {{10.1002/cne.22444}}
}
|
| Ruiz, A., Breton, J. & Llorente, J. ({2005}), "Theoretical support for buckyonions as carriers of the UV interstellar extinction feature" , PHYSICAL REVIEW LETTERS. , MAR 18, {2005}. Vol. {94} ({10}) |
| Abstract: Theoretically simulated UV-visible photoabsorption spectra of the buckyonions are compared with the most recent and complete experimental data. The very good agreement found provides support for our theoretical model of the buckyonions and allows for a detailed analysis of the correspondence between these spectra and the UV interstellar extinction feature. The excellent agreement found between the theoretical and observational features and the consistency of the former with the observational data constraints gives very strong support for the buckyonion origin of the UV interstellar spectrum. |
BibTeX:
@article{ISI:000227838900032,
author = {Ruiz, A and Breton, J and Llorente, JMG},
title = {Theoretical support for buckyonions as carriers of the UV interstellar extinction feature},
journal = {PHYSICAL REVIEW LETTERS},
year = {2005},
volume = {94},
number = {10},
doi = {{10.1103/PhysRevLett.94.105501}}
}
|
| Ruiz, A., Foronda, P., Gonzalez, J.F., Guedes, A., Abreu-Acosta, N., Molina, J.M. & Valladares, B. ({2008}), "Occurrence and genotype characterization of Giardia duodenalis in goat kids from the Canary Islands, Spain" , VETERINARY PARASITOLOGY. , JUN 14, {2008}. Vol. {154} ({1-2}) , pp. {137-141}. |
| Abstract: Giardia duodenalis (syn. Giardia lamblia, Giardia intestinalis) is a wide-spread intestinal protozoa of both humans and animals. Although giardiosis in goat is commonly asymptomatic, young kids may bear an enteric disease associated with persistent diarrhoea and delayed weight gain. In the present study we have analysed the occurrence of Giardia in 315 young goat kids (2-6 months old) from Gran Canaria Island (Spain) through visualization of faecal cysts. The identification of genotypes of G. duodenalis among the farms was attained by nested PCR of the triophosphate isomerase (TPI) and single PCR of P-giardin genes and subsequent sequencing. Positive samples were found in 42.2% of the animals and 95.5% of the farms. Goat faecal specimens were positive for only livestock-associated G. duodenalis assemblage E genotype for both TPI and P-giardin genes. The genetic analysis of these two loci revealed the presence of different haplotypes among the farms included in the survey and high homology with homologous genes from cattle and sheep. Altogether, the data presented here provide additional information to the prevalence and genetic characterization of Giardia isolates. The absence of assemblages A and B in this study suggests that zoonotic transmission of Giardia from goats could be of low epidemiological significance, although these findings should be validated in studies including other geographical areas, age groups and larger number of samples. (c) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000256552100018,
author = {Ruiz, Antonio and Foronda, Pilar and Gonzalez, Jorge F. and Guedes, Aranzazu and Abreu-Acosta, Nestor and Molina, Jose M. and Valladares, Basilio},
title = {Occurrence and genotype characterization of Giardia duodenalis in goat kids from the Canary Islands, Spain},
journal = {VETERINARY PARASITOLOGY},
year = {2008},
volume = {154},
number = {1-2},
pages = {137-141},
doi = {{10.1016/j.vetpar.2008.03.003}}
}
|
| Ruiz, A. & Heller, E. ({2006}), "Quasiresonance" , MOLECULAR PHYSICS. , JAN 10, {2006}. Vol. {104} ({1}) , pp. {127-145}. |
| Abstract: The concept of quasiresonance was introduced in connection with inelastic collisions between one atom and a vibro-rotationally excited diatomic molecule. In its original form, the collisions induce quasiresonant transfer of energy between the internal degrees of freedom of the diatom: there is a surprisingly accurate low order rational value for the ratio of the changes in the vibrational and rotational classical actions, provided the vibrational and rotational frequencies of the diatom are approximately related by low order rational values, and the collision was longer than the rotational period of the molecule. In this paper, we show that quasiresonance can be extended to many other processes and systems, and that it may be understood in terms of the adiabatic invariance theory and the method of averaging. |
BibTeX:
@article{ISI:000235149800013,
author = {Ruiz, A and Heller, EJ},
title = {Quasiresonance},
journal = {MOLECULAR PHYSICS},
year = {2006},
volume = {104},
number = {1},
pages = {127-145},
doi = {{10.1080/00268970500285029}}
}
|
| Ruiz, A. & Heller, E. ({2005}), "Quasiresonance: Switching enternal energy transfer on and off" , JOURNAL OF PHYSICAL CHEMISTRY A. , DEC 22, {2005}. Vol. {109} ({50}) , pp. {11578-11586}. |
| Abstract: Quasiresonance involves a slow ``external'' switching on and off of an interaction between internal degrees of freedom described by action-angle variables having approximate resonances. The resonances or near-resonances spawn slow coordinates that fail to be adiabatic, but the remaining coordinates may be fast enough to have conserved actions. The interaction either can be imposed externally as a time dependent coupling or can arise autonomously due to interactions with other degrees of freedom. A resonance transformation into slow and fast angles reveals the action corresponding to the fast angle is adiabatic and conserved to very high accuracy. This paper extends our work on quasiresonance to new systems and regimes, including the He-H-2 system, collisions with a periodic lattice, perturbative interactions, and discussion of quasiresonance in higher dimensional systems. |
BibTeX:
@article{ISI:000234119400032,
author = {Ruiz, A and Heller, EJ},
title = {Quasiresonance: Switching enternal energy transfer on and off},
journal = {JOURNAL OF PHYSICAL CHEMISTRY A},
year = {2005},
volume = {109},
number = {50},
pages = {11578-11586},
doi = {{10.1021/jp053724b}}
}
|
| Ruiz, A., Palao, J.P. & Heller, E.J. ({2009}), "Classical and quantum analysis of quasiresonance in grazing atom-surface collisions" , PHYSICAL REVIEW A. , MAY, {2009}. Vol. {79} ({5}) |
| Abstract: Quasiresonance is a general effect that may arise from the coupling between approximately resonant degrees of freedom in a system perturbed by some transient interaction. In a process induced by a slowly switching on and off of the coupling interaction, quasiresonance is characterized by the existence of significant ranges of initial states in the perturbed system over which some very specific and efficient transfer of energy between the approximately resonant degrees of freedom occurs. This work presents a classical and quantum analysis of quasiresonant processes in grazing incident angle atom-surface collisions. The momentum transfer between the normal components to an index direction is investigated. For fast atoms with grazing angle of incidence there is an interval of azimuthal angles around the index directions, the quasiresonance region, in which the energy transfer can be very efficient. This effect is reflected in quantum diffraction patterns with large nonspecular peaks, associated with the parallel to the surface and normal to the index direction momentum component. We demonstrate the essentially classical underlying mechanism for the persistence of a pattern of diffraction peak intensities for incidence close to an index direction. The analysis also shows that the size of the quasiresonance region is approximately equal to the spectral width of the diffraction pattern. |
BibTeX:
@article{ISI:000266500900106,
author = {Ruiz, Antonia and Palao, Jose P. and Heller, Eric J.},
title = {Classical and quantum analysis of quasiresonance in grazing atom-surface collisions},
journal = {PHYSICAL REVIEW A},
year = {2009},
volume = {79},
number = {5},
doi = {{10.1103/PhysRevA.79.052901}}
}
|
| Ruiz, A., Palao, J.P. & Heller, E.J. ({2009}), "Nearly resonant multidimensional systems under a transient perturbative interaction" , PHYSICAL REVIEW E. , DEC, {2009}. Vol. {80} ({6, Part 2}) |
| Abstract: We analyze the response of a classical system with N >= 2 internal degrees of freedom satisfying R <(N-1) approximated resonance conditions to an external perturbative transient interaction. Under certain assumptions on the system internal frequencies and on the coupling interaction, we show the precise N-R adiabatic invariants and obtain an estimate of the span of the domain defined by the intersecting resonances. The results are illustrated considering a system of three anharmonic oscillators transiently coupled by an explicitly time-dependent interaction, and applied to the low energy vibro-rotationally inelastic collisions between two diatomic molecules. |
BibTeX:
@article{ISI:000273228000081,
author = {Ruiz, Antonia and Palao, Jose P. and Heller, Eric J.},
title = {Nearly resonant multidimensional systems under a transient perturbative interaction},
journal = {PHYSICAL REVIEW E},
year = {2009},
volume = {80},
number = {6, Part 2},
doi = {{10.1103/PhysRevE.80.066606}}
}
|
| Ruiz, A., Palao, J.P. & Heller, E.J. ({2008}), "Quasiresonances in atom-surface collisions" , In 395TH WILHELM AND ELSE HERAEUS SEMINAR - TIME DEPENDENT PHENOMENA IN QUANTUM MECHANICS. Vol. {99} Note:395th We-Heraeus Seminar - Time-Dependent Phenomena in Quantum Mechanics, Blaubeuren, GERMANY, SEP 12-16, 2007. |
| Abstract: The only global autonomous system in which quasiresonant processes have been previously described is the seminal example of one atom colliding with a diatom molecule. In this work we describe classical quasiresonances in a different context, the grazing angle atom-surface collisions. While in the first system the actions related to the process correspond to the internal vibro-rotational degrees of freedom of the molecule, in this new example they turn to be the two components of the momentum of the atom parallel to the surface. We discuss the range of initial actions where quasiresonant processes arise, and suggest a new method to localize quasiresonance regions using the dwell time of the incoming atom in the vicinity of the surface. |
BibTeX:
@inproceedings{ISI:000284324800018,
author = {Ruiz, Antonia and Palao, Jose P. and Heller, Eric J.},
title = {Quasiresonances in atom-surface collisions},
booktitle = {395TH WILHELM AND ELSE HERAEUS SEMINAR - TIME DEPENDENT PHENOMENA IN QUANTUM MECHANICS},
year = {2008},
volume = {99},
note = {395th We-Heraeus Seminar - Time-Dependent Phenomena in Quantum Mechanics, Blaubeuren, GERMANY, SEP 12-16, 2007},
doi = {{10.1088/1742-6596/99/1/012018}}
}
|
| Ruiz-Fuertes, J., Errandonea, D., Lacomba-Perales, R., Segura, A., Gonzalez, J., Rodriguez, F., Manjon, F.J., Ray, S., Rodriguez-Hernandez, P., Munoz, A., Zhu, Z. & Tu, C.Y. ({2010}), "High-pressure structural phase transitions in CuWO4" , PHYSICAL REVIEW B. , JUN 29, {2010}. Vol. {81} ({22}) |
| Abstract: We study the effects of pressure on the structural, vibrational, and magnetic behavior of cuproscheelite. We performed powder x-ray diffraction and Raman spectroscopy experiments up to 27 GPa as well as ab initio total-energy and lattice-dynamics calculations. Experiments provide evidence that a structural phase transition takes place at 10 GPa from the low-pressure triclinic phase P1 to a monoclinic wolframite-type structure P2/c. Calculations confirmed this finding and indicate that the phase transformation involves a change in the magnetic order. In addition, the equation of state for the triclinic phase is determined: V-0=132.8(2) angstrom(3), B-0=139(6) GPa, and B-0(1)=4. Furthermore, experiments under different stress conditions show that nonhydrostatic stresses induce a second phase transition at 17 GPa and reduce the compressibility of CuWO4, B-0=171(6) GPa. The pressure dependence of all Raman modes of the triclinic and high-pressure phases is also reported and discussed. |
BibTeX:
@article{ISI:000279334600002,
author = {Ruiz-Fuertes, J. and Errandonea, D. and Lacomba-Perales, R. and Segura, A. and Gonzalez, J. and Rodriguez, F. and Manjon, F. J. and Ray, S. and Rodriguez-Hernandez, P. and Munoz, A. and Zhu, Zh. and Tu, C. Y.},
title = {High-pressure structural phase transitions in CuWO4},
journal = {PHYSICAL REVIEW B},
year = {2010},
volume = {81},
number = {22},
doi = {{10.1103/PhysRevB.81.224115}}
}
|
| Ruiz-Fuertes, J., Lopez-Moreno, S., Errandonea, D., Pellicer-Porres, J., Lacomba-Perales, R., Segura, A., Rodriguez-Hernandez, P., Munoz, A., Romero, A.H. & Gonzalez, J. ({2010}), "High-pressure phase transitions and compressibility of wolframite-type tungstates" , JOURNAL OF APPLIED PHYSICS. , APR 15, {2010}. Vol. {107} ({8}) |
| Abstract: This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. X-ray diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 16.7 GPa. This transition does not involve any change in the atomic coordination as confirmed by x-ray absorption measurements. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transitions upon further compression. Calculations have been also performed for wolframite-type MnWO4, which is found to have an antiferromagnetic configuration. In addition, our study reveals details of the local-atomic compression in MgWO4 and ZnWO4. In particular, below the transition pressure the ZnO6 and equivalent polyhedra tend to become more regular, whereas, the WO6 octahedra remain almost unchanged. Fitting the pressure-volume data we obtained the equation of state for the low-pressure phase of MgWO4 and ZnWO4. These and previous results on MnWO4 and CdWO4 are compared with the calculations. The compressibility of wolframite-type tungstates is also systematically discussed. Finally Raman spectroscopy measurements and lattice dynamics calculations are presented for MgWO4. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3380848] |
BibTeX:
@article{ISI:000277303200027,
author = {Ruiz-Fuertes, J. and Lopez-Moreno, S. and Errandonea, D. and Pellicer-Porres, J. and Lacomba-Perales, R. and Segura, A. and Rodriguez-Hernandez, P. and Munoz, A. and Romero, A. H. and Gonzalez, J.},
title = {High-pressure phase transitions and compressibility of wolframite-type tungstates},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2010},
volume = {107},
number = {8},
doi = {{10.1063/1.3380848}}
}
|
| Saib, S., Bouarissa, N., Rodrguez-Hernandez, P. & Munoz, A. ({2008}), "First-principles study of high-pressure phonon dispersions of wurtzite, zinc-blende, and rocksalt AlN" , JOURNAL OF APPLIED PHYSICS. , JAN 1, {2008}. Vol. {103} ({1}) |
| Abstract: We present ab initio calculations of the phonon dispersions and density of states for wurtzite, zinc-blende, and rocksalt AlN under hydrostatic pressure using density functional perturbation theory. The calculations predict the full phonon dispersions throughout the Brillouin zone. Out results regarding zone-center modes for wurtzite and zinc-blende structures show generally good agreement with Raman measurements and previous theoretical data. For rocksalt structure, the present results are predictions. The different behavior of the lattice vibration properties under pressure in the three phases being studied here is discussed. The pressure coefficients and mode Gruneisen parameters are determined from the pressure dependence of vibration modes. (c) 2008 American Institute of Physics. |
BibTeX:
@article{ISI:000252890700031,
author = {Saib, S. and Bouarissa, N. and Rodrguez-Hernandez, P. and Munoz, A.},
title = {First-principles study of high-pressure phonon dispersions of wurtzite, zinc-blende, and rocksalt AlN},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2008},
volume = {103},
number = {1},
doi = {{10.1063/1.2828151}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2010}), "Ab initio lattice dynamics and piezoelectric properties of MgS and MgSe alkaline earth chalcogenides" , EUROPEAN PHYSICAL JOURNAL B. , JAN, {2010}. Vol. {73} ({2}) , pp. {185-193}. |
| Abstract: We have studied structural, elastic, dielectric, vibrational, and piezoelectric properties of rock-salt and zinc-blende Mg alkaline earth chalcogenides (MgS, and MgSe) by using the plane-wave pseudopotential method within the local density approximation. The calculated lattice constant, bulk modulus, and elastic constants for these compounds are found to be in good agreement with experiment. The density functional perturbation theory has been employed to derive the Born effective charge and high-frequency dielectric constant and to calculate phonon dispersion curves and density of states. The piezoelectric constant has also been determined. The calculated results are compared with theory and experiment when available and showed reasonable agreement. In other cases, our results are predictions. The pressure dependence of the studied quantities has been examined and discussed. The pressure coefficients and mode Gruneisen parameters are determined. |
BibTeX:
@article{ISI:000274253100005,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Ab initio lattice dynamics and piezoelectric properties of MgS and MgSe alkaline earth chalcogenides},
journal = {EUROPEAN PHYSICAL JOURNAL B},
year = {2010},
volume = {73},
number = {2},
pages = {185-193},
doi = {{10.1140/epjb/e2009-00426-6}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2009}), "Lattice vibration spectrum of GaN from first-principle calculations" , SEMICONDUCTOR SCIENCE AND TECHNOLOGY. , FEB, {2009}. Vol. {24} ({2}) |
| Abstract: We report first-principle calculations in the framework of the density functional perturbation theory of the lattice vibration properties of GaN in the wurtzite and rocksalt phases at zero and under pressures ranging from 0 to 40 GPa. The calculations predict the full phonon spectrum throughout the Brillouin zone and phonon density of states. Generally, the calculated zone-center modes for the wurtzite structure are found to be in good agreement with previous theoretical and experimental results. For the phonons of rocksalt GaN in the presence of hydrostatic pressure, these are the first results to our knowledge. The pressure dependence of the zone-center optical frequencies is examined and discussed which allowed the calculation of the pressure coefficients and mode Gruneisen parameters. |
BibTeX:
@article{ISI:000262582700008,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Lattice vibration spectrum of GaN from first-principle calculations},
journal = {SEMICONDUCTOR SCIENCE AND TECHNOLOGY},
year = {2009},
volume = {24},
number = {2},
doi = {{10.1088/0268-1242/24/2/025007}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2008}), "Response to ``Comment on `First-principles study of high-pressure phonon dispersions of wurtzite, zinc-blende, and rocksalt AlN'" , JOURNAL OF APPLIED PHYSICS. , OCT 1, {2008}. Vol. {104} ({7}) |
BibTeX:
@article{ISI:000260125500176,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Response to ``Comment on `First-principles study of high-pressure phonon dispersions of wurtzite, zinc-blende, and rocksalt AlN'},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2008},
volume = {104},
number = {7},
doi = {{10.1063/1.2981201}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2008}), "Structural and dielectric properties of AlN under pressure" , PHYSICA B-CONDENSED MATTER. , NOV 30, {2008}. Vol. {403} ({21-22}) , pp. {4059-4062}. |
| Abstract: We use an ab initio total-energy pseuclopotential method within the local density approximation (LDA) to study the structural and dielectric properties of wurtzite, zinc-blende, and rocksalt aluminum nitride (AlN) under hydrostatic pressure. The ground-state properties are determined using a plane-wave pseudopotential method within density functional theory (DFT), while density functional perturbation theory (DFPT) is employed to derive the Born effective charges and high-frequency dielectric constants. Our results are in good agreement with available experimental and previous theoretical data. The pressure dependence of the studied quantities has been examined and discussed. For the rocksalt phase our results concerning dielectric properties are predictions and may serve as a reference for experimental work. (C) 2008 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000261605600040,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Structural and dielectric properties of AlN under pressure},
journal = {PHYSICA B-CONDENSED MATTER},
year = {2008},
volume = {403},
number = {21-22},
pages = {4059-4062},
doi = {{10.1016/j.physb.2008.08.007}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2007}), "Ab initio lattice dynamics of zinc-blende GaxIn1-xN alloys" , JOURNAL OF PHYSICS-CONDENSED MATTER. , DEC 5, {2007}. Vol. {19} ({48}) |
| Abstract: Using ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory within the local density approximation under the virtual crystal approximation, we present a theoretical study of the elastic and dielectric properties and zone-center optical phonons in zinc-blende GaxIn1-xN alloys over the whole composition range from pure InN to pure GaN. The computed values are generally in reasonably good agreement with the existing experimental data for both parent compounds InN and GaN and provide predictions for GaxIn1-xN in the composition range 0-1 (0 < x < 1). The compositional dependence of the elastic constants, Born effective charge, high-frequency dielectric constant and vibration modes was investigated. |
BibTeX:
@article{ISI:000251797600016,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Ab initio lattice dynamics of zinc-blende GaxIn1-xN alloys},
journal = {JOURNAL OF PHYSICS-CONDENSED MATTER},
year = {2007},
volume = {19},
number = {48},
doi = {{10.1088/0953-8984/19/48/486209}}
}
|
| Saib, S., Bouarissa, N., Rodriguez-Hernandez, P. & Munoz, A. ({2007}), "Structural properties of zinc-blende GaxIn1-xN: ab initio calculations" , EUROPEAN PHYSICAL JOURNAL B. , DEC, {2007}. Vol. {60} ({4}) , pp. {435-438}. |
| Abstract: We present a theoretical study of the structural properties, namely lattice constant, bulk modulus and its pressure derivative of zinc-blende GaxIn1-xN. The calculations are performed using first-principles calculations in the framework of the density-functional-theory within the local density approximation under the virtual crystal approximation. The computed values are in good agreement with the available experimental data. The composition dependence of the studied quantities is examined. Besides, the deviation of the alloy lattice constant from Vegard's law is evaluated. |
BibTeX:
@article{ISI:000252421200004,
author = {Saib, S. and Bouarissa, N. and Rodriguez-Hernandez, P. and Munoz, A.},
title = {Structural properties of zinc-blende GaxIn1-xN: ab initio calculations},
journal = {EUROPEAN PHYSICAL JOURNAL B},
year = {2007},
volume = {60},
number = {4},
pages = {435-438},
doi = {{10.1140/epjb/e2008-00015-3}}
}
|
| Sanchiz, J., Pasan, J., Fabelo, O., Lloret, F., Julve, M. & Ruiz-Perez, C. ({2010}), "[Cu-3(Hmesox)(3)](3-): a Precursor for the Rational Design of Chiral Molecule-Based Magnets (H(4)mesox=2-dihydroxymalonic acid)" , INORGANIC CHEMISTRY. , SEP 6, {2010}. Vol. {49} ({17}) , pp. {7880-7889}. |
| Abstract: Two new compounds K-3[Cu-3(Hmesox)(3)(H2O)]center dot 4H(2)O (1) and [(PPh4)(2)[CoCu3(Hmesox)(3)Cl] (2) [H(4)mesox = mesoxalic acid (2-dihydroxymalonic acid) and PPh4+ = tetraphenylphosphonium cation] have been prepared and magneto-structurally characterized. Compound 1 contains the [Cu-3(Hmesox)(3)](3-) entity which can be considered as a new precursor for molecular magnetism. In 1 the triangular arrangement of three copper(II) ions bridged by alkoxo groups are further connected to a symmetry-related tricopper(II) unit through a double oxo(carboxylate) bridge. The resulting hexacopper(II) entities are joined further through anti-syn carboxylate groups into an anionic threedimensional network of formula [Cu-3(Hmesox)(3)(H2O)(n)(3n-) whose charge is neutralized by univalent potassium cations. The strong decrease of the chi M T product [per three copper(II) ions] in the high temperature range with the occurrence of a plateau for a spin doublet at T < 65 K is as expected for the coexistence of two antiferromagnetic interactions within the quastisosceles tricopper(II),core of 1 [J = -194(1) cm(-1) and j = -3(4) cm(-1), the Hamiltonian being defined as H = -J(<(S)over cap>(1)center dot(S) over cap (2)center dot(S) over cap (3) - j((S) over cap (1)center dot(S) over cap (2))]. Compound 2 exhibits a chiral three-dimensional structure which is made up of an anionic [(CoCu3II)-Cu-II(mu(3)-Cl)(Hmesox)(3)(2n-) framework with a (10,3)-a topology whose cavities are filled by PPh4+ cations. The [Cu-3(II)(mu(3)-Cl)(Hmesox)(3)](3-) tricopper(II) unit in 2 acts as a tris-bidentate ligand through the Hmesox groups toward three cobalt(II) ions, these latter ones being tris-chelated. Alternating current (ac) and direct current (dc) magnetic susceptibility measurements of 2 show a ferrimagnetic behavior with a magnetic ordering at T-c = 18.5 K and a coercive field H-c = 5000 G. As shown by the magneto-structural study of 2, the use as a ligand of 1 versus metal ions other than cobalt(II) or preformed complexes whose coordination sphere is partially blocked represents a new and rational preparative route toward multifunctional heterometallic compounds. |
BibTeX:
@article{ISI:000281231800041,
author = {Sanchiz, Joaquin and Pasan, Jorge and Fabelo, Oscar and Lloret, Francesc and Julve, Miguel and Ruiz-Perez, Catalina},
title = {[Cu-3(Hmesox)(3)](3-): a Precursor for the Rational Design of Chiral Molecule-Based Magnets (H(4)mesox=2-dihydroxymalonic acid)},
journal = {INORGANIC CHEMISTRY},
year = {2010},
volume = {49},
number = {17},
pages = {7880-7889}
}
|
| Sans, J., Segura, A., Manjon, F., Mari, B., Munoz, A. & Herrera-Cabrera, M. ({2005}), "Optical properties of wurtzite and rock-salt ZnO under pressure" , MICROELECTRONICS JOURNAL. , OCT, {2005}. Vol. {36} ({10, Sp. Iss. SI}) , pp. {928-932}. Note:16th Latin American Symposium on Solid State Physics (SLAFES XVI), Merida, VENEZUELA, DEC 02-05, 2002. |
| Abstract: This paper reports on the pressure dependence of the optical absorption edge of ZnO in the wurtzite and rock-salt phase, up to 14 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films have been investigated. In both types of samples the wurtzite to rock-salt transition is observed at 9.7 +/- 0.2 GPa. The absorption tail of the fundamental gap, as measured in monocrystals, exhibits a pressure coefficient of 24.5 +/- 2 meV/GPa. The evolution under pressure of the full absorption edge of the wurtzite phase is studied with thin film samples, yielding a slightly lower pressure coefficient (23.0 +/- 0.5 meV/GPa for the A-B exciton). Rock-salt ZnO is shown to be an indirect semiconductor with a bandgap of 2.7 +/- 0.2 eV. At higher photon energy a direct transition (E-gd-4.5 eV) can be also identified in thin films transited to the rock-salt phase. Results on the high-pressure phase are interpreted on the basis of density-functional-theory (DFT) electronic structure calculations. (c) 2005 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000232252000013,
author = {Sans, JA and Segura, A and Manjon, FJ and Mari, B and Munoz, A and Herrera-Cabrera, MJ},
title = {Optical properties of wurtzite and rock-salt ZnO under pressure},
journal = {MICROELECTRONICS JOURNAL},
year = {2005},
volume = {36},
number = {10, Sp. Iss. SI},
pages = {928-932},
note = {16th Latin American Symposium on Solid State Physics (SLAFES XVI), Merida, VENEZUELA, DEC 02-05, 2002},
doi = {{10.1016/j.mejo.2005.05.010}}
}
|
| Santana-Alonso, A., Mendez-Ramos, J., Yanes, A.C., del Castillo, J. & Rodriguez, V.D. ({2010}), "Up-conversion in sol-gel derived nano-glass-ceramics comprising NaYF4 nano-crystals doped with Yb3+, Ho3+ and Tm3+" , OPTICAL MATERIALS. , JUL, {2010}. Vol. {32} ({9}) , pp. {903-908}. |
| Abstract: NaYF4 is an excellent host material for rare-earth ions presenting very high efficiencies in up-conversion processes. Thus, nano-glass-ceramics containing NaYF4 nano-crystals emerge as promising candidates for general lighting appliances and integrated optical devices. Here we report highly transparent sol-gel derived nano-glass-ceramics comprising Yb3+-Ho3+ and Yb3+-Ho3+-Tm3+ co-doped NaYF4 nano-crystals. A structural analysis by means of X-ray diffraction measurements confirmed the formation of NaYF4 nano-crystals during thermal treatment. Luminescence features have been related to the crystallinity degree of the samples. Violet, blue, green and red up-conversion emissions were obtained under infrared excitation at 980 nm and corresponding mechanisms involved have been analysed. Additionally, the total visible up-conversion emission has been quantified in terms of the standard chromaticity coordinates. In particular, an overall colour emission, very close to the standard equal energy white-light illumination point of the chromaticity diagram, was obtained in the Yb3+-Ho3+-Tm3+ triply-doped samples. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000279620900012,
author = {Santana-Alonso, A. and Mendez-Ramos, J. and Yanes, A. C. and del-Castillo, J. and Rodriguez, V. D.},
title = {Up-conversion in sol-gel derived nano-glass-ceramics comprising NaYF4 nano-crystals doped with Yb3+, Ho3+ and Tm3+},
journal = {OPTICAL MATERIALS},
year = {2010},
volume = {32},
number = {9},
pages = {903-908},
doi = {{10.1016/j.optmat.2010.01.020}}
}
|
| Santana-Alonso, A., Mendez-Ramos, J., Yanes, A.C., del Castillo, J. & Rodriguez, V.D. ({2010}), "White light up-conversion in transparent sol-gel derived glass-ceramics containing Yb3+-Er3+-Tm3+ triply-doped YF3 nanocrystals" , MATERIALS CHEMISTRY AND PHYSICS. , NOV 1, {2010}. Vol. {124} ({1}) , pp. {699-703}. |
| Abstract: Transparent glass-ceramics containing YF3 nanocrystals triply-doped with Yb3+- Er3+- Tm3+ ions have been successfully obtained under adequate thermal treatment of precursor sol gel glasses for the first time to our knowledge. X-ray diffraction and high resolution transmission electron microscopy analysis pointed out the precipitation of YF3 nanocrystals. Up-conversion luminescence features confirm the effective partition of luminescent ions into precipitated nanocrystals. Corresponding energy transfer up-conversion mechanisms and the dependence of the overall emitting colour have been analyzed as a function of doping ions, with varying concentration. In particular, very bright and efficient up-conversion emission, almost matching the standard equal energy white light illumination point of the standard chromaticity diagram, has been achieved showing up as promising candidate material for potential applications in photonic integrated devices and infrared tuneable phosphors. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000282607900125,
author = {Santana-Alonso, A. and Mendez-Ramos, J. and Yanes, A. C. and del-Castillo, J. and Rodriguez, V. D.},
title = {White light up-conversion in transparent sol-gel derived glass-ceramics containing Yb3+-Er3+-Tm3+ triply-doped YF3 nanocrystals},
journal = {MATERIALS CHEMISTRY AND PHYSICS},
year = {2010},
volume = {124},
number = {1},
pages = {699-703},
doi = {{10.1016/j.matchemphys.2010.07.038}}
}
|
| Santana-Alonso, A., Yanes, A.C., Mendez-Ramos, J., del Castillo, J. & Rodriguez, V.D. ({2011}), "Down-shifting by energy transfer in Dy3+-Tb3+ co-doped YF3-based sol-gel nano-glass-ceramics for photovoltaic applications" , OPTICAL MATERIALS. , FEB, {2011}. Vol. {33} ({4}) , pp. {587-591}. |
| Abstract: Highly transparent sot gel derived nano-glass-ceramics containing YF3 nanocrystals doped with Dy3+ or Tb3+ and co-doped with Dy3+-Tb3+ have been successfully developed. A structural analysis and luminescence spectra features confirmed the incorporation of rare-earth ions into precipitated YF3 nanocrystals, where efficient energy transfer from Dy3+ to Tb3+ takes place. Higher efficiency is obtained with increasing Tb3+ concentration, and no quenching effects are observed. Observed luminescence features leads the way to enhance solar cell spectral response by down-shifting of the incident solar spectrum, with an extended absorption range from 300 to 500 nm, yielding to a predominant green emission by co-doping with Dy3+ and Tb3+ ions. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000287629300001,
author = {Santana-Alonso, A. and Yanes, A. C. and Mendez-Ramos, J. and del-Castillo, J. and Rodriguez, V. D.},
title = {Down-shifting by energy transfer in Dy3+-Tb3+ co-doped YF3-based sol-gel nano-glass-ceramics for photovoltaic applications},
journal = {OPTICAL MATERIALS},
year = {2011},
volume = {33},
number = {4},
pages = {587-591},
doi = {{10.1016/j.optmat.2010.10.040}}
}
|
| Santana-Alonso, A., Yanes, A.C., Mendez-Ramos, J., del Castillo, J. & Rodriguez, V.D. ({2010}), "Sol-gel transparent nano-glass-ceramics containing Eu3+-doped NaYF4 nanocrystals" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , APR 15, {2010}. Vol. {356} ({18-19}) , pp. {933-936}. |
| Abstract: A spectroscopic study has been carried out in transparent nano-glass-ceramics containing Eu3+-doped NaYF4 nanocrystals, successfully developed for the first time by thermal treatment of precursor sol-gel derived glasses. X-ray diffraction and high-resolution transmission electron microscopy measurements confirmed the precipitation of NaYF4 nanocrystals during heat treatment and their corresponding sizes have been calculated by using Scherrer's equation and from electron microscopy measurements. Changes in the luminescence spectra with the temperature of the heat treatment have been analyzed and correlated with the crystallinity degree of the samples. In addition, emission spectra have been obtained for selected excitation wavelengths, observing large excitation selectivity among the fraction of the rare-earth ions located in near crystalline environments and those remaining in the silica glassy phase. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000276714000016,
author = {Santana-Alonso, A. and Yanes, A. C. and Mendez-Ramos, J. and del-Castillo, J. and Rodriguez, V. D.},
title = {Sol-gel transparent nano-glass-ceramics containing Eu3+-doped NaYF4 nanocrystals},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2010},
volume = {356},
number = {18-19},
pages = {933-936},
doi = {{10.1016/j.jnoncrysol.2009.12.023}}
}
|
| Santana-Alonso, A., Yanes, A.C., Mendez-Ramos, J., del Castillo, J. & Rodriguez, V.D. ({2009}), "Sol-gel transparent nano-glass-ceramics comprising rare-earth-doped NaYF4 nanocrystals" , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. , OCT, {2009}. Vol. {206} ({10}) , pp. {2249-2254}. Note:9th International Conference on Trends in Nanotechnology (TNT2008), Oviedo, SPAIN, SEP 01-05, 2008. |
| Abstract: Transparent nano-glass-ceramics containing rare-earth-doped NaYF4 nanocrystals (Eu3+ single-doped and Yb3+-Er3+ co-doped) have been successfully developed for the first time by thermal treatment of precursor bulk glasses obtained by sol-gel technique. X-ray diffraction and high-resolution transmission electron microscopy measurements reveal the precipitation of NaYF4 nanocrystals during the heat treatment and their corresponding sizes have been calculated. Luminescence measurements confirm the partition of rare-earth ions in NaYF4 nanocrystals. In Eu3+-doped samples, changes in the local environment of these rare-earth ions have been investigated by site-selective emission and excitation spectra. In Yb3+-Er3+ co-doped samples, efficient visible up-conversion luminescence has been obtained under infrared excitation at 980 nm. [GRAPHICS] The red to green up-conversion emission ratio can be varied as a function of temperature of heat treatment, resulting in colour tuneable up-conversion phosphors with applications in optical integrated devices. Colour tuneability has been analysed and quantified in terms of Comission Internationale d'Eclairage standard chromaticity diagram. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim |
BibTeX:
@article{ISI:000271605200006,
author = {Santana-Alonso, A. and Yanes, A. C. and Mendez-Ramos, J. and del-Castillo, J. and Rodriguez, V. D.},
title = {Sol-gel transparent nano-glass-ceramics comprising rare-earth-doped NaYF4 nanocrystals},
journal = {PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE},
year = {2009},
volume = {206},
number = {10},
pages = {2249-2254},
note = {9th International Conference on Trends in Nanotechnology (TNT2008), Oviedo, SPAIN, SEP 01-05, 2008},
doi = {{10.1002/pssa.200881717}}
}
|
| Santos, E., Monzon-Mayor, M., Romero-Aleman, M.M. & Yanes, C. ({2008}), "Distribution of neurotrophin-3 during the ontogeny and regeneration of the lizard (Gallotia galloti) visual system" , DEVELOPMENTAL NEUROBIOLOGY. , JAN, {2008}. Vol. {68} ({1}) , pp. {31-44}. |
| Abstract: We have previously described the spontaneous regeneration of retinal ganglion cell axons after optic nerve (ON) transection in the adult Gallotia galloti. As neurotrophin-3 (NT-3) is involved in neuronal differentiation, survival and synaptic plasticity, we performed a comparative immunohistochemical study of NT-3 during the ontogeny and regeneration (after 0.5, 1, 3, 6, 9, and 12 months postlesion) of the lizard visual system to reveal its distribution and changes during these events. For characterization of NT-3(+) cells, we performed double labelings using the neuronal markers HuC-D, Pax6 and parvalbumin (Parv), the microglial marker tomato lectin or Lycopersicon esculentum agglutinin (LEA), and the astroglial markers vimentin (Vim) and glial fibrillary acidic protein (GFAP). Subpopulations of retinal and tectal neurons were NT-3(+) from early embryonic stages to adulthood. Nerve fibers within the retinal nerve fiber layer, both plexiform layers and the retinorecipient layers in the optic tectum (OT) were also stained. In addition, NT-3(+)/GFAP(+) and NT-3(+)/ Vim(+) astrocytes were detected in the ON, chiasm and optic tract in postnatal and adult lizards. At I month postlesion, abundant NT-3(+)/GFAP(+) astrocytes and NT3(-)/LEA(+) microglia/macrophages were stained in the lesioned ON, whereas NT-3 became downregulated in the experimental retina and OT. Interestingly, at 9 and 12 months postlesion, the staining in the experimental retina resembled that in control animals, whereas bundles of putative regrown fibers showed a disorganized staining pattern in the OT. Altogether, we demonstrate that NT-3 is widely distributed in the lizard visual system and its changes after ON transection might be permissive for the successful axonal regrowth. (C) 2007 Wiley Periodicals, Inc. Develop Neurobiol 68: 31-44, 2008. |
BibTeX:
@article{ISI:000252349300003,
author = {Santos, E. and Monzon-Mayor, M. and Romero-Aleman, M. M. and Yanes, C.},
title = {Distribution of neurotrophin-3 during the ontogeny and regeneration of the lizard (Gallotia galloti) visual system},
journal = {DEVELOPMENTAL NEUROBIOLOGY},
year = {2008},
volume = {68},
number = {1},
pages = {31-44},
doi = {{10.1002/dneu.20566}}
}
|
| Santos, E., Romero-Aleman, M.M., Monzon-Mayor, M., Yanes, C. & Lang, D. ({2007}), "A comparative immunohistochemical study on BDNF distribution in the ontogeny and regeneration of the lizard (Gallotia galloti) visual system" , NEURON GLIA BIOLOGY. Vol. {2} ({Suppl. 1}) , pp. {S77}. |
BibTeX:
@article{ISI:000251708800238,
author = {Santos, E. and Romero-Aleman, M. M. and Monzon-Mayor, M. and Yanes, C. and Lang, D.},
title = {A comparative immunohistochemical study on BDNF distribution in the ontogeny and regeneration of the lizard (Gallotia galloti) visual system},
journal = {NEURON GLIA BIOLOGY},
year = {2007},
volume = {2},
number = {Suppl. 1},
pages = {S77}
}
|
| da Silva, I., Diaz, J.G. & Gonzalez-Platas, J. ({2011}), "Structure Determination of Monohydrated Trifolin (Kaempferol 3-O-beta-D-Galactopyranoside) from Laboratory Powder Diffraction Data" , JOURNAL OF PHARMACEUTICAL SCIENCES. , APR, {2011}. Vol. {100} ({4}) , pp. {1588-1593}. |
| Abstract: The crystal structure of monohydrated trifolin (kaempferol 3-O-beta-Dgalactopyranoside) (an important biologically active compound, which was isolated from the aerial part of Consolida oliveriana) has been determined from conventional laboratory X-ray powder diffraction data. Variable counting time technique was used during measurement and crystal structure was solved by means of Monte Carlo algorithm. The final structure was achieved by Rietveld refinement using both constraints and restraints on interatomic bond lengths and angles. (c) 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:1588-1593, 2011 |
BibTeX:
@article{ISI:000288516000033,
author = {da Silva, Ivan and Diaz, Jesus G. and Gonzalez-Platas, Javier},
title = {Structure Determination of Monohydrated Trifolin (Kaempferol 3-O-beta-D-Galactopyranoside) from Laboratory Powder Diffraction Data},
journal = {JOURNAL OF PHARMACEUTICAL SCIENCES},
year = {2011},
volume = {100},
number = {4},
pages = {1588-1593},
doi = {{10.1002/jps.22379}}
}
|
| da Silva, I., Gonzalez-Silgo, C., Gonzalez-Platas, J., Rodriguez-Carvajal, J., Martinez-Sarrion, M. & Mestres, L. ({2005}), "Neutron powder diffraction study of A(2)BeF(4) (A = K, Rb, Cs): Structure refinement and analysis of background" , JOURNAL OF SOLID STATE CHEMISTRY. , MAY, {2005}. Vol. {178} ({5}) , pp. {1601-1608}. |
| Abstract: The crystal structure of potassium, rubidium and caesium fluoroberyllates have been re-examined by neutron powder diffraction at room temperature and at 1.5 K. Previously, their structures, obtained from X-ray data, were described in the Pn2(1)a space group. However, the results obtained from Rietveld refinements, using powder neutron diffraction, at both temperatures, indicated that all structures are orthorhombic with space group Pnma. The known phase transition at high temperature is probably related to the appearance of a hexagonal pseudo-symmetry instead of the elimination of the mirror plane between the above mentioned orthorhombic space groups. A possible phase transition, at very low temperature, was discarded considering the stereochemical criteria concerning the structural stability of A(2)BX(4) compounds. This was confirmed by thermal analysis. On the other hand, a modulated background has been detected in all samples during the refinements. This is compatible with the presence of an amorphous phase, coexisting with the crystalline phase, or with a disordered component within the main crystalline phase. Instead of using a polynomial function, the background was modelled by Fourier filtering improving the fit for all patterns. The radial distribution function (RDF) was obtained from the analysis of the calculated background and compared with the RDF from the average crystal structure. The advantages of neutron with respect to X-ray diffraction were evidenced for this type of compound with β-K2SO4-type structure. © 2005 Elsevier Inc. All rights reserved. |
BibTeX:
@article{ISI:000228934800034,
author = {da Silva, I and Gonzalez-Silgo, C and Gonzalez-Platas, J and Rodriguez-Carvajal, J and Martinez-Sarrion, ML and Mestres, L},
title = {Neutron powder diffraction study of A(2)BeF(4) (A = K, Rb, Cs): Structure refinement and analysis of background},
journal = {JOURNAL OF SOLID STATE CHEMISTRY},
year = {2005},
volume = {178},
number = {5},
pages = {1601-1608},
doi = {{10.1016/j.jssc.2005.02.026}}
}
|
| da Silva, I., Gonzalez-Silgo, C., Gonzalez-Platas, J., Rodriguez-Carvajal, J., Martinez-Sarrion, M. & Mestres, L. ({2005}), "Powder neutron diffraction of Tl2BeF4 at six temperatures from room temperature to 1.5 K" , ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS. , DEC, {2005}. Vol. {61} ({Part 12}) , pp. {I113-I116}. |
| Abstract: The structure of thallium fluoroberyllate, Tl2BeF4, has been analysed by the Rietveld method on neutron diffraction patterns collected at 1.5, 50, 100, 150, 200 and 300 K, with the aim of detecting low-temperature instabilities. Atomic parameters based on the isomorphic beta-K2SO4 crystal in the paraelectric phase were used as the starting model at room temperature; no evidence for any phase transition has been detected at lower temperature. The structure was determined in the orthorhombic space group Pnma. All the atoms ( except one Fatom) occupy sites with m symmetry. We have compared the structure with those of other compounds of the beta-K2SO4 family, at room temperature, in order to gain insight into their observed instabilities. The irregular coordination of the cations may indicate stereochemical activity of the Tl-I lone pair but does not indicate a possible structural instability. |
BibTeX:
@article{ISI:000233747800001,
author = {da Silva, I and Gonzalez-Silgo, C and Gonzalez-Platas, J and Rodriguez-Carvajal, J and Martinez-Sarrion, ML and Mestres, L},
title = {Powder neutron diffraction of Tl2BeF4 at six temperatures from room temperature to 1.5 K},
journal = {ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS},
year = {2005},
volume = {61},
number = {Part 12},
pages = {I113-I116},
doi = {{10.1107/S010827010503249X}}
}
|
| Tejedor, D., Lopez-Tosco, S., Gonzalez-Platas, J. & Garcia-Tellado, F. ({2010}), "Tertiary Skipped Diynes: A Pluripotent Building Block for the Modular and Diversity-Oriented Synthesis of Nitrogen Heterocycles" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {16} ({11}) , pp. {3276-3280}. |
BibTeX:
@article{ISI:000276058100001,
author = {Tejedor, David and Lopez-Tosco, Sara and Gonzalez-Platas, Javier and Garcia-Tellado, Fernando},
title = {Tertiary Skipped Diynes: A Pluripotent Building Block for the Modular and Diversity-Oriented Synthesis of Nitrogen Heterocycles},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2010},
volume = {16},
number = {11},
pages = {3276-3280},
doi = {{10.1002/chem.200903577}}
}
|
| Tejedor, D., Lopez-Tosco, S., Gonzalez-Platas, J. & Garcia-Tellado, F. ({2009}), "From Conjugated Tertiary Skipped Diynes to Chain-Functionalized Tetrasubstituted Pyrroles" , CHEMISTRY-A EUROPEAN JOURNAL. Vol. {15} ({4}) , pp. {838-842}. |
BibTeX:
@article{ISI:000262886800003,
author = {Tejedor, David and Lopez-Tosco, Sara and Gonzalez-Platas, Javier and Garcia-Tellado, Fernando},
title = {From Conjugated Tertiary Skipped Diynes to Chain-Functionalized Tetrasubstituted Pyrroles},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2009},
volume = {15},
number = {4},
pages = {838-842},
doi = {{10.1002/chem.200802262}}
}
|
| Tejedor, D., Lopez-Tosco, S., Gonzalez-Platas, J. & Garcia-Tellado, F. ({2007}), "Metal-free access to fully substituted skipped diynes. An efficient chemodifferentiating A(2)BB ` 4CR manifold" , JOURNAL OF ORGANIC CHEMISTRY. , JUL 6, {2007}. Vol. {72} ({14}) , pp. {5454-5456}. |
| Abstract: A metal-free chemodifferentiating A(2)BB' 4CR manifold for the modular synthesis of tertiary skipped diynes is described. The manifold performs a triethylamine triggered reaction of alkyl propiolates and acid chlorides to assemble two units of each component in the form of two propargylic alkynoates, a tertiary alcohol, and an ester. A differentiated incorporation of the two acid chloride components ensures functional diversity in the final structure. In addition, the presence of two connected propargylic alkynoates provides a reactive platform for complexity generation. |
BibTeX:
@article{ISI:000247612200064,
author = {Tejedor, David and Lopez-Tosco, Sara and Gonzalez-Platas, Javier and Garcia-Tellado, Fernando},
title = {Metal-free access to fully substituted skipped diynes. An efficient chemodifferentiating A(2)BB ` 4CR manifold},
journal = {JOURNAL OF ORGANIC CHEMISTRY},
year = {2007},
volume = {72},
number = {14},
pages = {5454-5456},
doi = {{10.1021/jo070764y}}
}
|
| Tejedor, D., Mendez-Abt, G., Gonzalez-Platas, J., Ramirez, M.A. & Garcia-Tellado, F. ({2009}), "Ambiphilic allenes: synthesis and reactivity" , CHEMICAL COMMUNICATIONS. ({17}) , pp. {2368-2370}. |
| Abstract: Ambiphilic allenes are generated by an organocatalyzed domino reaction of alkyl propiolates and aromatic 1,2-diketones; in the absence of any external chemical agent, these allenes perform a thermally-driven dimerization reaction to generate the corresponding fully-substituted cyclobutanes in a regio- and highly stereoselective manner. |
BibTeX:
@article{ISI:000265355800033,
author = {Tejedor, David and Mendez-Abt, Gabriela and Gonzalez-Platas, Javier and Ramirez, Miguel A. and Garcia-Tellado, Fernando},
title = {Ambiphilic allenes: synthesis and reactivity},
journal = {CHEMICAL COMMUNICATIONS},
year = {2009},
number = {17},
pages = {2368-2370},
doi = {{10.1039/b819613c}}
}
|
| Tejedor, D., Santos-Exposito, A., Mendez-Abt, G., Ruiz-Perez, C. & Garcia-Tellado, F. ({2009}), "Trialkylamine versus Trialkylphosphine: Catalytic Conjugate Addition of Alcohols to Alkyl Propiolates" , SYNLETT. , MAY 15, {2009}. ({8}) , pp. {1223-1226}. |
| Abstract: The conjugate addition of activated propargylic alcohols to alkyl propiolates is shown to be catalyst-dependent. Whereas trialkylamines catalyze the expected 1,4-adition of the alcohol on the alkynoate to give the beta-alkoxyacrylate derivative, the trialkylphosphine-catalyzed reaction affords densely functionalized bicyclic hexahydrofuro[2,3-b]furan derivatives, A mechanistic proposal for the phosphine-catalyzed addition of alcohols to alkyl propiolates according with these observations is presented. |
BibTeX:
@article{ISI:000269443700004,
author = {Tejedor, David and Santos-Exposito, Alicia and Mendez-Abt, Gabriela and Ruiz-Perez, Catalina and Garcia-Tellado, Fernando},
title = {Trialkylamine versus Trialkylphosphine: Catalytic Conjugate Addition of Alcohols to Alkyl Propiolates},
journal = {SYNLETT},
year = {2009},
number = {8},
pages = {1223-1226},
doi = {{10.1055/s-0028-1216727}}
}
|
| Tikhomirov, V., Rodriguez, V., Mendez-Ramos, J., Nunez, P. & Seddon, A. ({2004}), "Comparative spectroscopy of (ErF3)(PbF2) alloys and Er3+-doped oxyfluoride glass-ceramics" , OPTICAL MATERIALS. , DEC, {2004}. Vol. {27} ({3}) , pp. {543-547}. |
| Abstract: We have prepared polycrystalline alloys x(ErF3):(100 - x)(PbF2), x = 1, 10. A comparison of their low temperature absorption and emission spectra with the respective spectra of transparent oxyfluoride glass-ceramics, 32(SiO2)9(AlO1.5)31.5(CdF2)18.5(PbF2)5.5(ZnF2):3.5(ErF3)mol indicates that the nano-crystalline phase in this glass-ceramic is Er3+-doped PbF2. (C) 2004 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000225675500034,
author = {Tikhomirov, VK and Rodriguez, VD and Mendez-Ramos, J and Nunez, P and Seddon, AB},
title = {Comparative spectroscopy of (ErF3)(PbF2) alloys and Er3+-doped oxyfluoride glass-ceramics},
journal = {OPTICAL MATERIALS},
year = {2004},
volume = {27},
number = {3},
pages = {543-547},
doi = {{10.1016/j.optmat.2004.07.004}}
}
|
| Tikhomirov, V.K., Adamo, G., Nikolaenko, A.E., Rodriguez, V.D., Gredin, P., Mortier, M., Zheludev, N.I. & Moshchalkov, V.V. ({2010}), "Cathodo- and photoluminescence in Yb3+-Er3+ co-doped PbF2 nanoparticles" , OPTICS EXPRESS. , APR 26, {2010}. Vol. {18} ({9}) , pp. {8836-8846}. |
| Abstract: We have prepared and studied the PbF2:(Yb3+,Er3+) co-doped nanoparticles, with chemical formula (Yb-Er)(x)Pb1-xF2+x, where x = 0.29, Yb3+/Er3+ = 6, and estimated the energy efficiency for their cathodoluminescence, mostly of Yb3+, and up-conversion photoluminescence of Er3+ to reach more than 0.5% and 20 respectively, which may be the highest to date for rare-earth doped nanoparticles. Electron beam induced temperature rise in the nanoparticles has been estimated by measuring the ratio of green emission bands of Er3+. These high efficiencies are due to high doping level of nanoparticles and due to low phonon energy of the PbF2 host. (C) 2010 Optical Society of America |
BibTeX:
@article{ISI:000277082200012,
author = {Tikhomirov, V. K. and Adamo, G. and Nikolaenko, A. E. and Rodriguez, V. D. and Gredin, P. and Mortier, M. and Zheludev, N. I. and Moshchalkov, V. V.},
title = {Cathodo- and photoluminescence in Yb3+-Er3+ co-doped PbF2 nanoparticles},
journal = {OPTICS EXPRESS},
year = {2010},
volume = {18},
number = {9},
pages = {8836-8846}
}
|
| Tikhomirov, V.K., Driesen, K., Rodriguez, V.D., Gredin, P., Mortier, M. & Moshchalkov, V.V. ({2009}), "Optical nanoheater based on the Yb3+-Er3+ co-doped nanoparticles" , OPTICS EXPRESS. , JUL 6, {2009}. Vol. {17} ({14}) , pp. {11794-11798}. |
| Abstract: Yb3+-Er3+ co-doped fluoride nanoparticles have been prepared. When pumped by 975 nm laser diode into absorption band of Yb3+, the laser-induced temperature rise up to 800 degrees C has been detected in the nanoparticles by measuring the ratio of the intensities of the thermalised up-conversion luminescence bands H-2(11/2)-> I-4(15/2) and S-4(3/2)-> I-4(15/2) of Er3+. These results show that a controlled optical heating of the nanoparticles and their surrounding nano-volumes can be realised, while the location and temperature rise of the nanoparticles and heated nano-volumes can be detected distantly by means of luminescence. (C) 2009 Optical Society of America |
BibTeX:
@article{ISI:000267761200058,
author = {Tikhomirov, V. K. and Driesen, K. and Rodriguez, V. D. and Gredin, P. and Mortier, M. and Moshchalkov, V. V.},
title = {Optical nanoheater based on the Yb3+-Er3+ co-doped nanoparticles},
journal = {OPTICS EXPRESS},
year = {2009},
volume = {17},
number = {14},
pages = {11794-11798}
}
|
| Tikhomirov, V.K., Mendez-Ramos, J., Rodriguez, V.D., Furniss, D. & Seddon, A.B. ({2007}), "Gain cross-sections of transparent oxyfluoride glass-ceramics single-doped with Ho3+ (at 2.0 mu m) and with Tm3+ (at 1.8 mu m)" , JOURNAL OF ALLOYS AND COMPOUNDS. , JUN 14, {2007}. Vol. {436} ({1-2}) , pp. {216-220}. |
| Abstract: We have developed transparent 3.5 mol% Ho3+ and TM3+ single-doped oxyfluoride glass-ceramics, where a large fraction of dopant ions is segregated into PbF2-based nano-crystals. The absorption and emission cross-sections corresponding to the I-5(7) <-> I-5(8) transitions of the Ho3+ (at 2.0 mu m), and to the H-3(6) <-> F-3(4) transitions of the TM3+ (at 1.8 mu m), have been obtained and respective gain cross-section spectra have been computed as a function of population inversion. For Ho3+-doped samples, the maximum gain cross-section increased by 20% on ceramming of the precursor glass and reached, for the ensuing glass-ceramics, a value 1.5 times higher than that reported for fluoride glasses. The maximum gain cross-section for Tm3+-doped samples increased 2.5 times on ceramming of the precursor glasses and reached for the ensuing glass-ceramics a value 2-3 times higher than for other fluoride hosts, such as ZBLAN glass, and 1.5 times higher than for silicate and germanate glass hosts. Hence, these Ho3+- and Tm3+-doped glass-ceramics have an advantage for application in planar and fibre lasers/amplifiers at about 2.0, and 1.8 mu m, respectively. (C) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000246349700041,
author = {Tikhomirov, V. K. and Mendez-Ramos, J. and Rodriguez, V. D. and Furniss, D. and Seddon, A. B.},
title = {Gain cross-sections of transparent oxyfluoride glass-ceramics single-doped with Ho3+ (at 2.0 mu m) and with Tm3+ (at 1.8 mu m)},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2007},
volume = {436},
number = {1-2},
pages = {216-220},
doi = {{10.1016/j.jallcom.2006.07.008}}
}
|
| Tikhomirov, V.K., Mendez-Ramos, J., Rodriguez, V.D., Furniss, D. & Seddon, A.B. ({2006}), "Laser and gain parameters at 2.7 mu m of Er3+-doped oxyfluoride transparent glass-ceramics" , OPTICAL MATERIALS. , JUL, {2006}. Vol. {28} ({10}) , pp. {1143-1146}. |
| Abstract: The room temperature emission spectrum at about 2.7 mu m corresponding to the laser transition I-4(11/2) -> I-4(13/2) in Er3+-doped nanoscaled transparent oxyfluoride glass-ceramic has been measured and stimulated emission cross-section for the transition has been calculated. The intensity of the transition has been found to be 40 times stronger and lifetime 50 times longer in the glass-ceramics compared to the precursor glass, which we show to be due to a change of frequency of the phonon involved in non-radiative de-excitation of the I-4(11/2) level from 900 cm(-1) in the precursor glass to 240 cm(-1) in the ensuing glass-ceramics. The absorption cross-section for the excited state absorption I-4(13/2) -> I-4(11/2) has been calculated based on the experimental reciprocal emission spectrum and wavelength dependence of the gain cross-section for the lasing transition I-4(11/2) -> I-4(13/2) vs population inversion has been derived. The lasing/optical amplification gain parameters, such as population inversion, pump saturation intensity and product of emission cross-section and fluorescence lifetime have been obtained at the 2.7 mu m wavelength. A noteworthy result is that laser action at 2.7 mu m is possible in these Er3+-doped glassceramics, already not taking into account energy transfer or up-conversion processes, related to the I-4(13/2) level, which favour the population inversion. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000238884000003,
author = {Tikhomirov, V. K. and Mendez-Ramos, J. and Rodriguez, V. D. and Furniss, D. and Seddon, A. B.},
title = {Laser and gain parameters at 2.7 mu m of Er3+-doped oxyfluoride transparent glass-ceramics},
journal = {OPTICAL MATERIALS},
year = {2006},
volume = {28},
number = {10},
pages = {1143-1146},
doi = {{10.1016/j.optmat.2005.06.017}}
}
|
| Tikhomirov, V.K., Rodriguez, V.D., Kuznetsov, A., Kirilenko, D., Van Tendeloo, G. & Moshchalkov, V.V. ({2010}), "Preparation and luminescence of bulk oxyfluoride glasses doped with Ag nanoclusters" , OPTICS EXPRESS. , OCT 11, {2010}. Vol. {18} ({21}) , pp. {22032-22040}. |
| Abstract: Bulk oxyfluoride glasses doped with Ag nanoclusters have been prepared using the melt quenching technique. When pumped in the absorption band of Ag nanoclusters between 300 to 500 nm, these glasses emit a very broad luminescence band covering all the visible range with a weak tail extending into the near infrared. The maximum of the luminescence band and its color shifts to the blue with a shortening of the excitation wavelength and an increasing ratio of oxide to fluoride components, resulting in white color luminescence at a particular ratio of oxide to fluoride; with a quantum yield above 20 (C) 2010 Optical Society of America |
BibTeX:
@article{ISI:000283686500057,
author = {Tikhomirov, V. K. and Rodriguez, V. D. and Kuznetsov, A. and Kirilenko, D. and Van Tendeloo, G. and Moshchalkov, V. V.},
title = {Preparation and luminescence of bulk oxyfluoride glasses doped with Ag nanoclusters},
journal = {OPTICS EXPRESS},
year = {2010},
volume = {18},
number = {21},
pages = {22032-22040}
}
|
| Toma, L., Lescouezec, R., Pasan, J., Ruiz-Perez, C., Vaissermann, J., Cano, J., Carrasco, R., Wernsdorfer, W., Lloret, F. & Julve, M. ({2006}), "[Fe(bpym)(CN)(4)](-): A new building block for designing single-chain magnets" , JOURNAL OF THE AMERICAN CHEMICAL SOCIETY. , APR 12, {2006}. Vol. {128} ({14}) , pp. {4842-4853}. |
| Abstract: We herein present the preparation, crystal structure, magnetic properties, and theoretical study of new heterobimetallic chains of formula [Fe-III(bpym)(CN4)](2)M-II(H2O)(2)center dot 6H(2)O [bpym = 2,2'-bipyrimidine; M = Zn (2), Co (3), Cu (4), and Mn (5)] which are obtained by using the building block PPh4[Fe(bpym)(CN)(4)]center dot H2O (1) (PPh4+ = tetraphenylphosphonium) as a ligand toward the fully solvated M-II ions. The structure of complex 1 contains mononuclear [Fe(bpym)(CN)(4)](-) anions. Compounds 2-5 are isostructural 4,2-ribbonlike bimetallic chains where the [Fe(bpym)(CN)(4)](-) unit acts as a bis-monodenate ligand through two of its four cyanide ligands toward the M atom. Water hexamer clusters (4) and regular alternating fused six- and four-membered water rings with two dangling water molecules (2, 3, and 5) are trapped between the cyanide-bridged 4,2-ribbonlike chains. 1 and 2 behave as magnetically isolated low-spin iron(III) centers. 3 behaves as a single-chain magnet (SCM) with intrachain ferromagnetic coupling, slow magnetic relaxation, hysteresis effects, and frequency-dependent ac signals at T < 7 K. As expected for a thermally activated process, the nucleation field (H-n) in 3 increases with decreasing T and increasing v. Below 1.0 K, H-n becomes temperature independent but remains strongly sweep rate dependent. In this temperature range, the reversal of the magnetization may be induced by a quantum nucleation of a domain wall that then propagates due to the applied field. 4 and 5 are ferro- and ferrimagnetic chains respectively, with metamagnetic-like behavior (4). DFT-type calculations and QMC methodology provided a good understanding of the magnetic properties of 3-5. |
BibTeX:
@article{ISI:000236770300075,
author = {Toma, LM and Lescouezec, R and Pasan, J and Ruiz-Perez, C and Vaissermann, J and Cano, J and Carrasco, R and Wernsdorfer, W and Lloret, F and Julve, M},
title = {[Fe(bpym)(CN)(4)](-): A new building block for designing single-chain magnets},
journal = {JOURNAL OF THE AMERICAN CHEMICAL SOCIETY},
year = {2006},
volume = {128},
number = {14},
pages = {4842-4853},
doi = {{10.1021/ja058030v}}
}
|
| Toma, L., Lescouezec, R., Vaissermann, J., Delgado, F., Ruiz-Perez, C., Carrasco, R., Cano, J., Lloret, F. & Julve, M. ({2004}), "Nuclearity controlled cyanide-bridged bimetallic Cr-III-Mn-II compounds: Synthesis, crystal structures, magnetic properties and theoretical calculations" , CHEMISTRY-A EUROPEAN JOURNAL. , DEC 3, {2004}. Vol. {10} ({23}) , pp. {6130-6145}. |
| Abstract: The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4- [Cr(bipy)(CN)(4)].2CH(3)CN.H2O (1) (mononuclear), [Cr(bipy)(CN)(4)(2)Mn(H2O)(4)].4H(2)O (2) (trinuclear), [Cr(bipy)(CN)(4)(2)Mn(H2O)(2)] (3) (chain) and [Cr(bipy)(CN)(4)(2)Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4+ = tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)(4)](-) unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4, two chains of 3 are pillared through interchain Mn-N-C-Cr links which replace one of the two trans-coordinated water molecules at the manganese atom to afford a double chain structure where bis- and tris-monodenate coordination modes of [Cr(bipy)(CN)(4)](-) coexist. The magnetic properties of 1-4 were investigated in the temperature range 1.9-300 K. A Curie law behaviour for a magnetically isolated spin quartet is observed for 1. A significant antiferromagnetic interaction between Cr-III and Mn-II through the single cyanide bridge [J = -6.2 cm(-1), the Hamiltonian being defined as I = -J((S) over cap (Cr(1)).(S) over cap (Mn)+(S) over cap (Cr(2)).(S) over cap (Mn))] occurs in 2 leading to a low-lying spin doublet which is fully populated at T < 5 K. A metamagnetic behaviour is observed for 3 and 4 [the values of the critical field H-c being ca. 3000 (3) and 1500 Oe (4)] which is associated to the occurrence of weak interchain antiferromagnetic interactions between ferrimagnetic (Cr2MnII)-Mn-III chains. The analysis of the exchange pathways in 2-4 through DFT type calculations together with the magnetic bevaviour simulation using the quantum Monte Carlo methodology provided a good understanding of their magnetic properties. |
BibTeX:
@article{ISI:000225486800025,
author = {Toma, L and Lescouezec, R and Vaissermann, J and Delgado, FS and Ruiz-Perez, C and Carrasco, R and Cano, J and Lloret, F and Julve, M},
title = {Nuclearity controlled cyanide-bridged bimetallic Cr-III-Mn-II compounds: Synthesis, crystal structures, magnetic properties and theoretical calculations},
journal = {CHEMISTRY-A EUROPEAN JOURNAL},
year = {2004},
volume = {10},
number = {23},
pages = {6130-6145},
doi = {{10.1002/chem.200400611}}
}
|
| Toma, L., Lescouezec, R., Vaissermann, J., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2005}), "Complex as ligand strategy in designing nuclearity controlled cyanide-bridged heterometallic compounds." , ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY. , MAR 13, {2005}. Vol. {229} ({Part 1}) , pp. {372-INOR}. Note:229th National Meeting of the American-Chemical-Society, San Diego, CA, MAR 13-17, 2005. |
BibTeX:
@article{ISI:000228177707371,
author = {Toma, LM and Lescouezec, R and Vaissermann, J and Ruiz-Perez, C and Lloret, F and Julve, M},
title = {Complex as ligand strategy in designing nuclearity controlled cyanide-bridged heterometallic compounds.},
journal = {ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY},
year = {2005},
volume = {229},
number = {Part 1},
pages = {372-INOR},
note = {229th National Meeting of the American-Chemical-Society, San Diego, CA, MAR 13-17, 2005}
}
|
| Toma, L.M., Toma, L.D., Delgado, F.S., Ruiz-Perez, C., Sletten, J., Cano, J., Clemente-Juan, J.M., Lloret, F. & Julve, M. ({2006}), "Trans-dicyanobis(acetylacetonato)ruthenate(III) as a precursor to build novel cyanide-bridged Ru-III-M-II bimetallic compounds [M = Co and Ni]" , COORDINATION CHEMISTRY REVIEWS. , SEP, {2006}. Vol. {250} ({17-18, Sp. Iss. SI}) , pp. {2176-2193}. Note:20th International Conference on Coordination and Bioinorganic Chemistry (ICCBiC), Smolenice, SLOVAKIA, JUN 05-10, 2005. |
| Abstract: The use of the mononuclear complex trans-[Ru(acac)(2)(CN)(2)](-) as a ligand towards the preformed species [Ni2L(H2O)(2)Cl-2], [Co(dmphen)](NO3)(2), [Ni(dmphen)](NO3)(2) and [Co(H2O)(6)](NO3)(2) afforded the novel cyanide-bridged bimetallic compounds of formula [Ru(acac)(2)(CN)(2)Ni-2 (L)(H2O)(2)]Ru(acac)(2)(CN)(2)(.)2H(2)O (1), [Ru(acac)(2)(CN)(2)Co(dmphen)(NO3)](H2O)-H-. (2) and [Ru(acac)(2)(CN)(2)Ni(dmphen)(NO3)](H2O)-H-. (3) and [Ru(acac)(2)(CN)(2)(2)Co] (4) [Hacac = acetylacetone, dmphen = 2,9-dimethylphenanthroline and H2L = 11,23-dimethyl-3,7,15,19-tetrazatricyclo[19.3.1.1(9,13)]hexacosa-2,7,9 ,11,13(26),14,19,21(25),22,24-decaene-25,26-diol]. Their syntheses, X-ray crystal structures and magnetic properties are reported here. The structure of 1 consists of cationic cyanide-bridged chains of formula [Ru(acac)(2)(CN)(2) Ni-2(L)(H2O)(2)](+) and mononuclear anions [Ru(acac)(2)(CN)(2)](-). Compounds 2 and 3, which are isostructural, are made up of cyanide-bridged neutral chains [fRu(acac)(2)(CN)(2)M(dmphen)(NO3)] with regular alternating ruthenium(III) and cobalt(II) (2)/nickel(II) (3) ions. Each cobalt atom in 4 is tetrahedrally coordinated by four [Ru-III(acac)(2)(CN)(2)](-) ions through the cyano nitrogen atoms to afford a two-fold interpenetrated (6,4) three-dimensional network which is formed by 12 gon cycles having six ruthenium and six cobalt atoms. The metal-metal separations through the cyanide bridge are 5.2491(1) angstrom for 1, 5.2038(12) and 5.2426(12) angstrom for 2, 5.2130(12) and 5.2253(12) angstrom for 3 and 5.1155(15) and 5.1100(15) angstrom for 4. The magnetic properties of 1-4 together with those of the mononuclear precursor trans-PPh4[Ru(acac)(2)(CN)(2)] (PPh4+ = tetraphenylphosphonium cation and Hacac = acetylacetone) were investigated in the temperature range 1.9-295 K. The cyano-bearing ruthenium(III) precursor exhibits the magnetic behavior expected for a low-spin distorted octahedral ruthenium(III) system with spin-orbit coupling of the T-2(2g) ground term. Compound 1 exhibits an overall antiferromagnetic behavior, the magnetic coupling between the nickel(II) ions through the double phenoxo group and that between adjacent ruthenium(III) and nickel(II) centers through the single cyano bridge being -50.0 and +6.6 cm(-1), respectively. Compounds 2 and 3 behave as ferromagnetic chains. The intrachain magnetic coupling in 3 is +3.2 cm(-1) whereas that in 2 could not be evaluated because of the lack of a suitable model. No magnetic ordering is observed in 2 and 3 down to 1.9 K. Compound 4 shows an overall ferromagnetic behavior and it exhibits ferromagnetic ordering at Tc = 5.4 K. Theoretical calculations based on density functional theory (DFT) have been employed on the trans- [Ru(acac)(2)(CN)(2)](-) mononuclear complex and on dinuclear fragments of the compounds 1-3 in order to analyze the efficiency of the exchange pathways through the double phenoxo (1) and single cyano ridge (1-3) and to substantiate the exchange coupling. parameters involved. (c) 2006 Elsevier B.V All rights reserved. |
BibTeX:
@article{ISI:000240282400002,
author = {Toma, Luminita Marilena and Toma, Liviu Dan and Delgado, Fernando S. and Ruiz-Perez, Catalina and Sletten, Jorunn and Cano, Joan and Clemente-Juan, Juan Modesto and Lloret, Francesc and Julve, Miguel},
title = {Trans-dicyanobis(acetylacetonato)ruthenate(III) as a precursor to build novel cyanide-bridged Ru-III-M-II bimetallic compounds [M = Co and Ni]},
journal = {COORDINATION CHEMISTRY REVIEWS},
year = {2006},
volume = {250},
number = {17-18, Sp. Iss. SI},
pages = {2176-2193},
note = {20th International Conference on Coordination and Bioinorganic Chemistry (ICCBiC), Smolenice, SLOVAKIA, JUN 05-10, 2005}
}
|
| Torres, F.J., Rodriguez-Mendoza, U.R., Lavin, V., de Sola, E.R. & Alarcon, J. ({2007}), "Evolution of the structural and optical properties from cobalt cordierite glass to glass-ceramic based on spinel crystalline phase materials" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , NOV 15, {2007}. Vol. {353} ({44-46}) , pp. {4093-4101}. |
| Abstract: CO2+-containing cordierite stoichiometric glasses have been prepared by melting colloidal gel precursors. After controlled thermal processing in the range of temperatures between 900 and 1300 degrees C different polycrystalline, almost single phase materials displaying mu-, alpha-, and P-cordierite crystalline forms were synthesized. In addition, spinet glass-ceramic materials were also prepared from the base glasses. All these materials were characterized by X-ray powder diffraction and infrared spectroscopy. Room temperature (RT) absorption and emission spectra of Co2+-cordierites and - spinel-glass material have allowed determining the local environment of the Co2+ in the crystalline structure of final materials. Results indicated that whereas in parent glasses and in the t-cordierite forms there are a large fraction of CO2+ in octahedral coordination, in the low (beta-) and high (alpha-) temperature crystalline forms the proportion of Co2+ in tetrahedral coordination increased. The final CoAl2O4-glass composite showed absorption and emission spectra very similar to the sol-gel CoAl2O4 spinet, both displaying pure Co2+ tetrahedral coordination. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000250971900012,
author = {Torres, F. J. and Rodriguez-Mendoza, U. R. and Lavin, V. and de Sola, E. Ruiz and Alarcon, J.},
title = {Evolution of the structural and optical properties from cobalt cordierite glass to glass-ceramic based on spinel crystalline phase materials},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2007},
volume = {353},
number = {44-46},
pages = {4093-4101},
doi = {{10.1016/j.jnoncrysol.2007.06.014}}
}
|
| Torres, M.E., Kaminskii, A.A., Gonzalez-Silgo, C., Platas, J.G., Jaque, D., Rodenas, A., Martin, I.R. & Lavin, V. ({2008}), "Dielectric anomalies in Nd3+ doped Ba2NaNb5O15 laser crystal" , JOURNAL OF ALLOYS AND COMPOUNDS. , FEB 28, {2008}. Vol. {451} ({1-2}) , pp. {198-200}. Note:6th International Conference on f-Elements (ICFE-6), Wroclaw, POLAND, SEP 04-09, 2006. |
| Abstract: In the present study we analyze the thermal and dielectric behavior from 292 to 930 K of BNN doped with Nd3+ (1 at.. The crystal was grown by the Czochralski method along the tetragonal axis. The complicated dielectric permittivity epsilon'(r) behavior, which depends on the cooling or heating process, was compared with the pure crystal. Two unexpected epsilon'(r) anomalies were detected around 318 and 847 K while the remaining transitions are in good agreement with the thermal expansion measurements. (c) 2007 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000253600400043,
author = {Torres, M. E. and Kaminskii, A. A. and Gonzalez-Silgo, C. and Platas, J. Gonzalez and Jaque, D. and Rodenas, A. and Martin, I. R. and Lavin, V.},
title = {Dielectric anomalies in Nd3+ doped Ba2NaNb5O15 laser crystal},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2008},
volume = {451},
number = {1-2},
pages = {198-200},
note = {6th International Conference on f-Elements (ICFE-6), Wroclaw, POLAND, SEP 04-09, 2006},
doi = {{10.1016/j.jallcom.2007.04.176}}
}
|
| Triana, J., Lopez, M., Perez, F., Gonzalez-Platas, J., Quintana, J., Estevez, F., Leon, F. & Bermejo, J. ({2005}), "Sesquiterpenoids from Pulicaria canariensis and their cytotoxic activities" , JOURNAL OF NATURAL PRODUCTS. , APR, {2005}. Vol. {68} ({4}) , pp. {523-531}. |
| Abstract: Thirteen new sesquiterpenes, pulicanadiene A (1), B (2), and C (3), pulicanone (4), pulicanol (5), pulicanarals A (6), B (7), and C (8), pulicanadienals A (9) and B (10), pulicanadienol (11), and pulioplopanones A (12) and B (13), and seven known compounds, stigmasterol, ergosterol peroxide, calenduladiol, 7,4'-di-O-methyldihydrokaempferol, 5,7-dihydroxy-3,3',4'-trimethoxyflavone, dihydroquercetin 7,3'-dimethyl ether, and 6,15 alpha-epoxy-1 beta,4 beta-dihydroxyeudesmane, were isolated from Pulicaria canariensis. Compound 4a showed cytotoxicity on the human myeloid leukemia cell line HL-60. The cytotoxicity was caused by induction of apoptosis as determined by microscopy of nuclear changes, activation of caspases, and the cleavage of poly(ADP-ribose) polymerase-1. |
BibTeX:
@article{ISI:000228677000009,
author = {Triana, J and Lopez, M and Perez, FJ and Gonzalez-Platas, J and Quintana, J and Estevez, F and Leon, F and Bermejo, J},
title = {Sesquiterpenoids from Pulicaria canariensis and their cytotoxic activities},
journal = {JOURNAL OF NATURAL PRODUCTS},
year = {2005},
volume = {68},
number = {4},
pages = {523-531},
doi = {{10.1021/np0496183}}
}
|
| Unal, B., Netti, M., Hassan, M., Ayliffe, P., Charlton, M., Lahoz, F., Perney, N., Shepherd, D., Tai, C., Wilkinson, J. & Parker, G. ({2005}), "Neodymium-doped tantalum pentoxide waveguide lasers" , IEEE JOURNAL OF QUANTUM ELECTRONICS. , DEC, {2005}. Vol. {41} ({12}) , pp. {1565-1573}. |
| Abstract: The fabrication, spectroscopic properties, and laser performance of Nd3+ -doped Ta2O5 channel waveguide lasers are described. Lasing is obtained at both 1.066 and 1.375 mu m with threshold pump powers as low as 2.7 mW. The rib waveguides are reactive-ion-etched into Nd:Ta2O5 layers formed by reactive magnetron sputtering. These high-index low-loss rare-earth-doped waveguides are fabricated on silicon substrates and offer the potential for integration with photonic crystal structures for compact optical circuits. |
BibTeX:
@article{ISI:000233574400018,
author = {Unal, B and Netti, MC and Hassan, MA and Ayliffe, PJ and Charlton, MDB and Lahoz, F and Perney, NMB and Shepherd, DP and Tai, CY and Wilkinson, JS and Parker, GJ},
title = {Neodymium-doped tantalum pentoxide waveguide lasers},
journal = {IEEE JOURNAL OF QUANTUM ELECTRONICS},
year = {2005},
volume = {41},
number = {12},
pages = {1565-1573},
doi = {{10.1109/JQE.2005.858775}}
}
|
| Vallejo, J., Castro, I., Ferrando-Soria, J., del Pino Deniz-Hernandez, M., Ruiz-Perez, C., Lloret, F., Julve, M., Ruiz-Garcia, R. & Cano, J. ({2011}), "Solid-State Dinuclear-to-Trinuclear Conversion in an Oxalato-Bridged Chromium(III)-Cobalt(II) Complex as a New Route toward Single-Molecule Magnets" , INORGANIC CHEMISTRY. , MAR 21, {2011}. Vol. {50} ({6}) , pp. {2073-2075}. |
| Abstract: A novel bis(oxalato)chromium(III) salt of a ferromagnetically coupled, oxalato-bridged dinuclear chromium(III)-cobalt(II) complex of formula [CrL(ox)(2)-CoL'(H2O)(2)] [CrL(ox)(2)]center dot 4H(2)O (1) has been self-assembled in solution using different aromatic alpha,alpha'-diimines as blocking ligands, such as 2,2'-bipyridine (L bpy) and 2,9-dimethyl-1,10-phenanthroline (L' = Me(2)phen). Thermal dehydration of 1 leads to an intriguing solid-state reaction between the S = 3/2 Cr-III anions and the S = 3 (CrCoII)-Co-III cations to give a ferromagnetically coupled, oxalato-bridged trinuclear chromium(III)-cobalt(II) complex of formula [CrL(ox)(2)](2)CoL' (2). Complex 2 possesses a moderately anisotropic S = 9/2 (Cr2CoII)-Co-III ground state, and it exhibits slow magnetic relaxation behavior at very low temperatures (T-B < 2.0 K). |
BibTeX:
@article{ISI:000288182700013,
author = {Vallejo, Julia and Castro, Isabel and Ferrando-Soria, Jesus and del Pino Deniz-Hernandez, Maria and Ruiz-Perez, Catalina and Lloret, Francesc and Julve, Miguel and Ruiz-Garcia, Rafael and Cano, Joan},
title = {Solid-State Dinuclear-to-Trinuclear Conversion in an Oxalato-Bridged Chromium(III)-Cobalt(II) Complex as a New Route toward Single-Molecule Magnets},
journal = {INORGANIC CHEMISTRY},
year = {2011},
volume = {50},
number = {6},
pages = {2073-2075},
doi = {{10.1021/ic1025203}}
}
|
| Van der Werff, P., Martinez-Ferrero, E., Batten, S., Jensen, P., Ruiz-Perez, C., Almeida, M., Waerenborgh, J., Cashion, J., Moubaraki, B., Galan-Mascaros, J., Martinez-Agudo, J., Coronado, E. & Murray, K. ({2005}), "Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*M-2][M `(dca)(3)]" , DALTON TRANSACTIONS. ({2}) , pp. {285-290}. |
| Abstract: A new series of hybrid materials of type [Cp*M-2][M'(dca)(3)] has been prepared by cation templation and structurally characterised (M = Fe(III), Co(III); M' = Mn(II), Fe(II), Co(II), Ni(II), Cd(II); dca(-) = N(CN)(2)(-)). The crystallographic analysis of [Cp*Fe-2][Cd(dca)(3)] showed that the [Cd(dca)(3)](-) anionic framework is of a symmetrical 3-D alpha-polonium type, containing octahedral Cd nodes and mu(1,5)-dca bridging ligands. The [Cp*Fe-2](+) cations occupy the cube-like cavities within the framework. The cationic and anionic-framework sublattices remain magnetically independent and display susceptibilities, over the range 300 to 2 K, of a Curie-Weiss nature obtained by adding a S = 1/2 (Cp*Fe-2(+)) or a S = 0 (Cp*Co-2(+)) contribution to those of the weakly antiferromagnetically coupled frameworks of M'. These hybrid species do not show any intrinsic long-range magnetic order. The present [Cp*Fe-2][M'(dca)(3)] series display the characteristic, unusually shaped [Cp*Fe-2](+) Mossbauer line, in the range 295-5 K, assigned (below 101 K) as the sum of a narrow and a broad line. Relaxation effects were evident. The [Fe(dca)(3)](-) compound showed superimposed low-spin Fe(III) and high-spin Fe(II) lines, the latter giving relaxation broadening effects. |
BibTeX:
@article{ISI:000225889400010,
author = {Van der Werff, PM and Martinez-Ferrero, E and Batten, SR and Jensen, P and Ruiz-Perez, C and Almeida, M and Waerenborgh, JC and Cashion, JD and Moubaraki, B and Galan-Mascaros, JR and Martinez-Agudo, JM and Coronado, E and Murray, KS},
title = {Hybrid materials containing organometallic cations and 3-D anionic metal dicyanamide networks of type [Cp*M-2][M `(dca)(3)]},
journal = {DALTON TRANSACTIONS},
year = {2005},
number = {2},
pages = {285-290},
doi = {{10.1039/b415275a}}
}
|
| Vasko, F., Hernandez-Cabrera, A. & Aceituno, P. ({2005}), "Temporal stimulated intersubband emission of photoexcited electrons" , PHYSICAL REVIEW B. , JUN, {2005}. Vol. {71} ({24}) |
| Abstract: We have studied the transient evolution of electrons distributed over two levels in a wide quantum well, with the two levels below the optical phonon energy, after an ultrafast interband excitation and cascade emission of optical phonons. If electrons are distributed near the top of the passive region, a temporal negative absorption appears to be dominant in the intersubband response. This is due to the effective broadening of the upper level state under the optical phonon emission. We have then considered the amplification of the ground mode in a THz waveguide with a multiquantum well placed at the center of the cavity. A huge increase of the probe signal is obtained, which permits the temporal stimulated emission regime of the photoexcited electrons in the THz spectral region. |
BibTeX:
@article{ISI:000230276900080,
author = {Vasko, FT and Hernandez-Cabrera, A and Aceituno, P},
title = {Temporal stimulated intersubband emission of photoexcited electrons},
journal = {PHYSICAL REVIEW B},
year = {2005},
volume = {71},
number = {24},
doi = {{10.1103/PhysRevB.71.245325}}
}
|
| Vasko, F.T., Hernandez-Cabrera, A. & Aceituno, P. ({2008}), "Transient quantum evolution of two-dimensional electrons under photoexcitation of a deep center" , PHYSICAL REVIEW B. , FEB, {2008}. Vol. {77} ({7}) |
| Abstract: We have considered the ballistic propagation of the two-dimensional (2D) electron Wigner distribution, which is excited by an ultrashort optical pulse from a deep center into the first quantized subband of a selectively doped heterostructure with high mobility. Transient ionization of a local state into a continuum conduction band state is described. Since the quantum nature of the photoexcitation, the Wigner distribution over 2D plane appears to be an alternating-sign function. Due to the negative contribution of the Wigner function, the mean values (concentration, energy, and flow) demonstrate an oscillating transient evolution in contrast to the diffusive classical regime of propagation. |
BibTeX:
@article{ISI:000253764200090,
author = {Vasko, F. T. and Hernandez-Cabrera, A. and Aceituno, P.},
title = {Transient quantum evolution of two-dimensional electrons under photoexcitation of a deep center},
journal = {PHYSICAL REVIEW B},
year = {2008},
volume = {77},
number = {7},
doi = {{10.1103/PhysRevB.77.075310}}
}
|
| de Vega, I. & Alonso, D. ({2008}), "Emission spectra of atoms with non-Markovian interaction: Fluorescence in a photonic crystal" , PHYSICAL REVIEW A. , APR, {2008}. Vol. {77} ({4}) |
| Abstract: We present a formula to evaluate the spontaneous emission spectra of an atom in contact with a radiation field with non-Markovian effects. This formula is written in terms of a two-time correlation of system observables and the environmental correlation function, and depends on the distance between the emitting atom and the detector. As an example, we use it to analyze the fluorescence spectra of a two level atom placed as an impurity in a photonic crystal. The radiation field within those materials has a gap or discontinuity where electromagnetic modes cannot propagate in the stationary limit. In that situation, the atomic emission occurs in the form of evanescent waves which are detected with less efficiency the farther we place the detector. The methodology presented in this paper may be useful to study the non-Markovian dynamics of any quantum open system in linear interaction with a harmonic oscillator reservoir and within the weak-coupling approximation. |
BibTeX:
@article{ISI:000255457100192,
author = {de Vega, Ines and Alonso, Daniel},
title = {Emission spectra of atoms with non-Markovian interaction: Fluorescence in a photonic crystal},
journal = {PHYSICAL REVIEW A},
year = {2008},
volume = {77},
number = {4},
doi = {{10.1103/PhysRevA.77.043836}}
}
|
| de Vega, I. & Alonso, D. ({2006}), "Non-Markovian reduced propagator, multiple-time correlation functions, and master equations with general initial conditions in the weak-coupling limit" , PHYSICAL REVIEW A. , FEB, {2006}. Vol. {73} ({2}) |
| Abstract: In this paper we derive the evolution equation for the reduced propagator, an object that evolves vectors of the Hilbert space of a system S interacting with an environment B in a non-Markovian way. This evolution is conditioned to certain initial and final states of the environment. Once an average over these environmental states is made, reduced propagators permit the evaluation of multiple-time correlation functions of system observables. When this average is done stochastically the reduced propagator evolves according to a stochastic Schrodinger equation. In addition, it is possible to obtain the evolution equations of the multiple-time correlation functions which generalize the well-known quantum regression theorem to the non-Markovian case. Here, both methods, stochastic and evolution equations, are described by assuming a weak coupling between system and environment. Finally, we show that reduced propagators can be used to obtain a master equation with general initial conditions, and not necessarily an initial vacuum state for the environment. We illustrate the theory with several examples. |
BibTeX:
@article{ISI:000235668100027,
author = {de Vega, I and Alonso, D},
title = {Non-Markovian reduced propagator, multiple-time correlation functions, and master equations with general initial conditions in the weak-coupling limit},
journal = {PHYSICAL REVIEW A},
year = {2006},
volume = {73},
number = {2},
doi = {{10.1103/PhysRevA.73.022102}}
}
|
| de Vega, I., Alonso, D. & Gaspard, P. ({2005}), "Two-level system immersed in a photonic band-gap material: A non-Markovian stochastic Schrodinger-equation approach" , PHYSICAL REVIEW A. , FEB, {2005}. Vol. {71} ({2}) |
| Abstract: It is our aim to study the dynamics of a two-level atom immersed in the modified radiation field of a photonic band-gap material using non-Markovian stochastic Schrodinger equations. Up to now, such methodology has only been applied to toy models and not to physically realistic systems as the one presented here. In order to check its validity, we shall study several of the physical phenomena already described in the literature within non-Markovian master equations, such as the long-time-limit residual population in the excited level of the atom and the population inversion which occurs in the atomic system when applying an external laser field. In addition to the stochastic equation, we propose a non-Markovian master equation derived from the stochastic formalism, which in contrast to the current models of master equation preserves positivity. We propose a correlation function for the radiation field (environment) that captures many of the physically relevant aspects of the problem and describes the short-time behavior in a more accurate way than previously proposed ones. This characteristic permits a correct description of the fluctuations of the electromagnetic field, which in the stochastic formalism are represented by the noise, and a better description of the non-Markovian effects in the atomic dynamics. The methodology presented in this paper to apply stochastic Schrodinger equations can be followed to study more complex systems, like many-level atoms embedded in more complicated photonic band-gap structures. |
BibTeX:
@article{ISI:000227483900113,
author = {de Vega, I and Alonso, D and Gaspard, P},
title = {Two-level system immersed in a photonic band-gap material: A non-Markovian stochastic Schrodinger-equation approach},
journal = {PHYSICAL REVIEW A},
year = {2005},
volume = {71},
number = {2},
doi = {{10.1103/PhysRevA.71.023812}}
}
|
| de Vega, I., Alonso, D., Gaspard, P. & Strunz, W. ({2005}), "Non-Markovian stochastic Schrodinger equations in different temperature regimes: A study of the spin-boson model" , JOURNAL OF CHEMICAL PHYSICS. , MAR 22, {2005}. Vol. {122} ({12}) |
| Abstract: Stochastic Schrodinger equations are used to describe the dynamics of a quantum open system in contact with a large environment, as an alternative to the commonly used master equations. We present a study of the two main types of non-Markovian stochastic Schrodinger equations, linear and nonlinear ones. We compare them both analytically and numerically, the latter for the case of a spin-boson model. We show in this paper that two linear stochastic Schrodinger equations, derived from different perspectives by Diosi, Gisin, and Strunz [Phys. Rev. A 58, 1699 (1998)], and Gaspard and Nagaoka [J. Chem. Phys. 13, 5676 (1999)], respectively, are equivalent in the relevant order of perturbation theory. Nonlinear stochastic Schrodinger equations are in principle more efficient than linear ones, as they determine solutions with a higher weight in the ensemble average which recovers the reduced density matrix of the quantum open system. However, it will be shown in this paper that for the case of a spin-boson system and weak coupling, this improvement does only occur in the case of a bath at high temperature. For low temperatures, the sampling of realizations of the nonlinear equation is practically equivalent to the sampling of the linear ones. We study further this result by analyzing, for both temperature regimes, the driving noise of the linear equations in comparison to that of the nonlinear equations. |
BibTeX:
@article{ISI:000228287900006,
author = {de Vega, I and Alonso, D and Gaspard, P and Strunz, WT},
title = {Non-Markovian stochastic Schrodinger equations in different temperature regimes: A study of the spin-boson model},
journal = {JOURNAL OF CHEMICAL PHYSICS},
year = {2005},
volume = {122},
number = {12},
doi = {{10.1063/1.1867377}}
}
|
| Velazquez, J.J., Rodriguez, V.D., Yanes, A.C., del Castillo, J. & Mendez-Ramos, J. ({2010}), "Increase in the Tb3+ green emission in SiO2-LaF3 nano-glass-ceramics by codoping with Dy3+ ions" , JOURNAL OF APPLIED PHYSICS. , DEC 1, {2010}. Vol. {108} ({11}) |
| Abstract: 95SiO(2)-5LaF(3) sol-gel derived nano-glass-ceramics single doped with 0.1Dy(3+) or 0.1Tb(3+) mol % and codoped with 0.1Dy(3+) and xTb3+ (x = 0.1, 0.3) mol % were successfully obtained. XRD and HRTEM measurements confirm the precipitation of LaF3 nanocrystals during the ceramming process, with mean size ranging from 10 to 20 nm and increasing with the thermal treatment temperature. About 75% of lanthanide ions are partitioned into LaF(3)s nanocrystals, as calculated from luminescence decays. The effect of increasing the Tb3+ concentration and also of codoping with Dy3+ in the Tb3+ green emission from the D-5(4) level have been studied. The energy transfer mechanisms between Tb3+ ions and also between Tb3+-Dy3+ ions, which favor the green emission, have been analyzed. (c) 2010 American Institute of Physics. [doi: 10.1063/1.3514552] |
BibTeX:
@article{ISI:000285474100058,
author = {Velazquez, J. J. and Rodriguez, V. D. and Yanes, A. C. and del-Castillo, J. and Mendez-Ramos, J.},
title = {Increase in the Tb3+ green emission in SiO2-LaF3 nano-glass-ceramics by codoping with Dy3+ ions},
journal = {JOURNAL OF APPLIED PHYSICS},
year = {2010},
volume = {108},
number = {11},
doi = {{10.1063/1.3514552}}
}
|
| Velazquez, J.J., Yanes, A.C., del Castillo, J., Mendez-Ramos, J. & Rodriguez, V.D. ({2010}), "Spectroscopic characterization and up-conversion in sol-gel derived Yb3+-Pr3+ co-doped SiO2-LaF3 nano-glass-ceramics" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , JUN 1, {2010}. Vol. {356} ({25-27}) , pp. {1349-1353}. |
| Abstract: The up-conversion of near infrared photons into the visible range is of major interest for lighting appliances and photonic integrated devices. Here we report up-conversion luminescence in transparent nano-glass-ceramics with composition of 95SiO(2)-5LaF(3) co-doped with 0.1 mol% of Pr3+ and 0.3 mol% of Yb3+, which were synthesized by different thermal treatments of precursor sol-gel glasses. Precipitation of LaF3 nanocrystals during ceramming process was confirmed by means of X-ray diffraction and the partition of rare-earth ions into them has been analyzed. The effect of increasing thermal treatment temperature and adding Yb3+ ions in the degree of crystallinity of the samples has been discussed. Efficient up-conversion emissions were observed under infrared excitation of the Yb3+ ions in the co-doped Yb3+-Pr3+ samples, while it was hardly detected in single Pr3+-doped samples. (C) 2010 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000279571400025,
author = {Velazquez, J. J. and Yanes, A. C. and del-Castillo, J. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Spectroscopic characterization and up-conversion in sol-gel derived Yb3+-Pr3+ co-doped SiO2-LaF3 nano-glass-ceramics},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2010},
volume = {356},
number = {25-27},
pages = {1349-1353},
doi = {{10.1016/j.jnoncrysol.2010.03.001}}
}
|
| Velazquez, J.J., Yanes, A.C., del Castillo, J., Mendez-Ramos, J. & Rodriguez, V.D. ({2007}), "Optical properties of Ho3+-Yb3+ co-doped nanostructured SiO2-LaF3 glass-ceramics prepared by sol-gel method" , PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. , JUN, {2007}. Vol. {204} ({6}) , pp. {1762-1768}. Note:7th International Conference on Trends in Nanotechnology (TNT 2006), Grenoble, FRANCE, SEP 04-08, 2006. |
| Abstract: Transparent glass-ceramics with composition of 95SiO(2)-5LaF(3) doped with 0.1 mol% of Ho3+ or co-doped with 0.1 mol% of Ho3+ and 0.3 mol% of Yb3+ were synthesized by thermal treatment of precursor sol-gel glasses. Segregation of LaF3, nanocrystals in the matrix was confirmed from a structural analysis by means of X-ray diffraction. Blue, green and red efficient up-conversion emissions were observed under 980 nm excitation at room temperature. These results could be attributed to the partition of a fraction of Ho3+ ions into the precipitated LaF3 nanocrystals. Moreover, near infrared down-conversion at 1.2 mu m is also observed. The mechanisms involved in the up-conversion emissions could be ascribed to a two- and threephoton process. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. |
BibTeX:
@article{ISI:000247542500025,
author = {Velazquez, J. J. and Yanes, A. C. and del Castillo, J. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Optical properties of Ho3+-Yb3+ co-doped nanostructured SiO2-LaF3 glass-ceramics prepared by sol-gel method},
journal = {PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE},
year = {2007},
volume = {204},
number = {6},
pages = {1762-1768},
note = {7th International Conference on Trends in Nanotechnology (TNT 2006), Grenoble, FRANCE, SEP 04-08, 2006},
doi = {{10.1002/pssa.200675349}}
}
|
| Venkatramu, V., Babu, P., Martin, I.R., Lavin, V., Munoz-Santiuste, J.E., Troester, T., Sievers, W., Wortmann, G. & Jayasankar, C.K. ({2010}), "Role of the local structure and the energy trap centers in the quenching of luminescence of the Tb3+ ions in fluoroborate glasses: A high pressure study" , JOURNAL OF CHEMICAL PHYSICS. , MAR 21, {2010}. Vol. {132} ({11}) |
| Abstract: The concentration and pressure dependent luminescence properties of the Tb3+ ions in a lithium fluoroborate glasses have been studied by analyzing the deexcitation processes of the D-5(4) level at ambient conditions as well as a function of pressure up to 35 GPa at room temperature. The luminescence spectra of Tb3+ ions have been measured as a function of pressure and observed a continuous redshift as well as a progressive increase in the magnitude of the crystal-field splittings for the D-5(4)-> F-7(3,4,5) transitions. Monitoring the D-5(4)-> F-7(5) transition, the luminescence decay curves have been measured and analyzed in order to understand the dynamics of the deexcitation of the Tb3+ ions in these glasses. At ambient conditions a nonexponential behavior has been found for doping concentrations as low as 0.1 mol % of Tb4O7, although no cross-relaxation channels exist to explain this behavior. The modelization of the energy transfer processes surprisingly shows that the nonexponential character of the decay curves of the D-5(4) level with concentration or with pressure has to be ascribed to energy transfer to traps without migration of energy between Tb3+ ions. For all the experimental situations the nonexponential character of the decay curves is well described by the generalized Yokota-Tanimoto model with a dipole-dipole interaction between the Tb3+ ions and the nearby luminescence quenching traps. The luminescence properties observed with releasing pressure are slightly different to those obtained while increasing pressure suggesting a local structural hysteresis in the lithium fluoroborate glass matrix giving rise to the generation of a new distribution of environments for the Tb3+ ions. |
BibTeX:
@article{ISI:000275825500034,
author = {Venkatramu, V. and Babu, P. and Martin, I. R. and Lavin, V. and Munoz-Santiuste, Juan E. and Troester, Th. and Sievers, W. and Wortmann, G. and Jayasankar, C. K.},
title = {Role of the local structure and the energy trap centers in the quenching of luminescence of the Tb3+ ions in fluoroborate glasses: A high pressure study},
journal = {JOURNAL OF CHEMICAL PHYSICS},
year = {2010},
volume = {132},
number = {11},
doi = {{10.1063/1.3352631}}
}
|
| Venkatramu, V., Navarro-Urrios, D., Babu, P., Jayasankar, C. & Lavin, V. ({2005}), "Fluorescence line narrowing spectral studies of Eu3+-doped lead borate glass" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , APR 15, {2005}. Vol. {351} ({10-11}) , pp. {929-935}. |
| Abstract: A lead borate glass of molar composition 49.5H(3)BO(3)-49.5PbO-1.0Eu(2)O(3) was prepared and studied by broadband and fluorescence line narrowing spectral techniques. Site-selective D-5(0) &RARR; F-7(0.1) emission spectra were obtained under resonant excitation at different wavelengths along the F-7(0) &RARR; D-5(0) transition. These studies have been used to investigate the site-to-site variations in the spectroscopic properties of Eu3+ ions in the lead borate glass at 13 K. The energies of the Stark levels of the F-7(1) multiplets are obtained from the experimental fluorescence line narrowing spectra and crystal-field analysis has been carried out, assuming C-2v orthorhombic symmetry, for each of the excitation energies. The distribution environments and the local structures of Eu3+ ions in lead borate glass are found to be almost similar to calcium diborate glass and lies intermediate between Eu3+-doped sodium borosilicate and lithium fluoroborate glasses. © 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000228953100020,
author = {Venkatramu, V and Navarro-Urrios, D and Babu, P and Jayasankar, CK and Lavin, V},
title = {Fluorescence line narrowing spectral studies of Eu3+-doped lead borate glass},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2005},
volume = {351},
number = {10-11},
pages = {929-935},
doi = {{10.1016/j.jnoncrysol.2005.02.010}}
}
|
| Venkatramu, V., Vijaya, R., Leon-Luis, S.F., Babu, P., Jayasankar, C.K., Lavin, V. & Dhareshwar, L.J. ({2011}), "Optical properties of Yb3+- doped phosphate laser glasses" , JOURNAL OF ALLOYS AND COMPOUNDS. , APR 21, {2011}. Vol. {509} ({16}) , pp. {5084-5089}. |
| Abstract: Ytterbium-doped phosphate glasses have been prepared and studied their spectroscopic properties through absorption, emission and Fourier transform infrared (FTIR) spectral studies and time-resolved luminescence decay curves. The absorption cross-section has been found to vary with the variation of Yb2O3 concentration. The results of the FTIR spectra show that the OH- content is increasing with increase of the Yb2O3 concentration in these glasses. The decay curves of the F-2(5/2) level of Yb3+ ions exhibit a single exponential nature for all the concentrations. The lifetimes of the F-2(5/2) level of Yb3+ ions decreases from 1.04 to 0.27 ms when the Yb2O3 concentration is increased from 0.1 to 6.0 mol The quenching of lifetimes has been found to vary directly with the inter-ionic distance between the Yb3+ ions. The concentration quenching of the lifetime has been analyzed using different energy transfer processes and no evidence of cooperative luminescence of Yb3+ ions has been found in these glasses, which reveals that the present glasses are useful for photonic device applications. The laser performance properties have also been evaluated for these glasses and compared with those of other reported Yb3+-doped glass systems. (C) 2011 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000289372300014,
author = {Venkatramu, V. and Vijaya, R. and Leon-Luis, S. F. and Babu, P. and Jayasankar, C. K. and Lavin, V. and Dhareshwar, L. J.},
title = {Optical properties of Yb3+- doped phosphate laser glasses},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2011},
volume = {509},
number = {16},
pages = {5084-5089},
doi = {{10.1016/j.jallcom.2011.01.148}}
}
|
| Vinoly, R., Yanes, C., Romero-Aleman, M.M., Santos, E., Monzon-Mayor, M.M., Casanas, N. & Alfayate, C.M. ({2009}), "ORIGIN AND DISTRIBUTION OF MICROGLIAL CELLS DURING THE ONTOGENY AND REGENERATION OF THE LIZARD OPTIC NERVE" , GLIA. , OCT, {2009}. Vol. {57} ({13, Suppl. S}) , pp. {S154-S155}. Note:9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009. |
BibTeX:
@article{ISI:000270075500635,
author = {Vinoly, R. and Yanes, C. and Romero-Aleman, M. M. and Santos, E. and Monzon-Mayor, M. M. and Casanas, N. and Alfayate, C. M.},
title = {ORIGIN AND DISTRIBUTION OF MICROGLIAL CELLS DURING THE ONTOGENY AND REGENERATION OF THE LIZARD OPTIC NERVE},
journal = {GLIA},
year = {2009},
volume = {57},
number = {13, Suppl. S},
pages = {S154-S155},
note = {9th European Meeting on Glial Cells in Health and Disease, Paris, FRANCE, SEP 08-12, 2009}
}
|
| Visinescu, D., Fabelo, O., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2010}), "[Fe(phen)(CN)(4)](-): a suitable metalloligand unit to build 3d-4f heterobimetallic complexes with mixed bpym-cyano bridges (phen=1,10-phenantroline, bpym=2,2 `-bipyrimidine)" , CRYSTENGCOMM. Vol. {12} ({8}) , pp. {2454-2465}. |
| Abstract: The synthesis, crystal structure and magnetic properties of a new series of mixed 3d-4f complexes with the formula [Fe-III(phen)(CN)(3)(mu-CN)(4)Ln(2)(III)(NO3)(2)(H2O)(6)(mu-bpym)] center dot nH(2)O [Ln = Eu (1), Gd (2), Dy (3) and Ho (4); n = 8 (1, 3 and 4) and 11 (2); phen = 1,10-phenantroline; bpym = 2,2'-bipyrimidine] are discussed here. Compounds 1-4 are centrosymmetric hexanuclear species whose structure is made up of two cyano-bridged Fe(2)(III)Ln(III) heterobimetallic moieties which are connected through a bis-bidentate bpym molecule between the two rare-earth centers. The values of the iron-lanthanide distance across the single cyano-bridge are Fe(1)center dot center dot center dot Eu(1) = 5.5587(8) and Fe(2)center dot center dot center dot Eu(1) = 5.4908(8) angstrom (1), Fe(1)center dot center dot center dot Gd(1) = 5.5456(6) and Fe(2)center dot center dot center dot Gd(1) = 5.4831(6) angstrom (2), Fe(1)center dot center dot center dot Dy(1) = 5.5223(7) and Fe(2)center dot center dot center dot Dy(1) = 5.4509(7) angstrom (3) and Fe(1)center dot center dot center dot Ho(1) = 5.5094(12) and Fe(2)center dot center dot center dot Ho(1) = 5.4420(14) angstrom (4), whereas those of the lanthanide-lanthanide separation through the bpym bridge are 6.8196(8) (1), 6.7971(6) (2), 6.7511(7) (3) and 6.7395(6) angstrom (4). The two crystallographically independent iron(III) ions in 1-4 are six-coordinated with two nitrogen atoms from a bidentate phen ligand and four carbon atoms from four cyanide groups building somewhat distorted octahedral surroundings. The trivalent lanthanide cations in 1-4 are nine-coordinated with two bpym and two cyano-nitrogen atoms, three water molecules and a chelating nitrate describing distorted monocapped square antiprism environments. Compounds 1-4 are isomorphous species where the neutral hexanuclear motifs are assembled through an extensive network of hydrogen bonds involving all the water molecules to afford a supramolecular three-dimensional structure. Interestingly, the crystal packing of 2 shows the occurrence of unprecedented centrosymmetric twelve-atom water aggregates which are integrated by two interlinked pentanuclear water rings, each one having a dangling water molecule. The investigation of the magnetic properties of 1-4 in the temperature range 1.9-300 K reveals the presence of intramolecular magnetic interactions for 2-4 [antiferro- (through single cyano and bpym bridges) in 2 and ferromagnetic (across single cyano and/or bpym bridges) in 3 and 4] whereas the magnetic behaviour of 1 corresponds to that of the magnetically isolated low-spin iron(III) and europium(III) centers. |
BibTeX:
@article{ISI:000280204900027,
author = {Visinescu, Diana and Fabelo, Oscar and Ruiz-Perez, Catalina and Lloret, Francesc and Julve, Miguel},
title = {[Fe(phen)(CN)(4)](-): a suitable metalloligand unit to build 3d-4f heterobimetallic complexes with mixed bpym-cyano bridges (phen=1,10-phenantroline, bpym=2,2 `-bipyrimidine)},
journal = {CRYSTENGCOMM},
year = {2010},
volume = {12},
number = {8},
pages = {2454-2465},
doi = {{10.1039/c002305a}}
}
|
| Visinescu, D., Marilena Toma, L., Cano, J., Fabelo, O., Ruiz-Perez, C., Labrador, A., Lloret, F. & Julve, M. ({2010}), "Magnetic coupling in discrete cyano-bridged Mn-III-Fe-III motifs: Synthesis, crystal structure, magnetic properties and theoretical study" , DALTON TRANSACTIONS. Vol. {39} ({20}) , pp. {5028-5038}. |
| Abstract: The preparation, crystal structures and magnetic properties of the heterobimetallic complexes of formula [Mn-III(n-MeOsalen)(H2O)(mu-CN)Fe-III(bpym)(CN)(3)]center dot mH(2)O with n = m = 3 (1) and n = 4 and m = 2 (2) [n-MeOsalen(2-) = N,N'-ethylenebis(n-methoxysalicylideneiminate) dianion and bpym = 2,2'-bipyrimidine] are reported. 1 and 2 are dinuclear neutral species where the cyano-bearing low-spin unit [Fe-III(bpym)(CN)(4)](-) acts as a monodentate ligand towards the [Mn-III(SB)(solv)(x)](+) entity (SB = tetradentate Schiff-base) through one of its four cyano groups. Adjacent heterobimetallic units are interlinked through hydrogen bonds involving the coordinated water molecule of one dinuclear unit and the phenolate oxygen atoms of the neighbouring one to afford pairs of dimers with values of the interdimer Mn center dot center dot center dot Mn distance of 4.925(20) (1) and 5.0508(25) angstrom (2). The analysis of the magnetic data of 1 and 2 in the temperature range 1.9-300 K shows the coexistence of weak ferro- [J = + 2.95 (1) and + 3.88 cm(-1) (2)] and antiferromagnetic interactions [j = -1.91 (1) and -0.70 cm(-1) (2)] through the single cyano bridge and hydrogen bonds, respectively (the Hamiltonian being of the type (H) over cap = J[(S) over cap (Fe)center dot(S) over cap (Mn) + (S) over cap (Fe),center dot(S) over cap (Mn)] - -j (S) over cap (Mn)center dot(S) over cap (Mn)). Theoretical calculations using methods based on density functional theory (DFT) have been used to substantiate the nature and magnitude of the magnetic coupling observed in 1 and 2 and also to analyze the dependence of the magnetic coupling on the structural parameters for the Fe-C-N-Mn skeleton. An extension of the calculations to selected examples of heterobimetallic Fe-III-C-N-Mn-III compounds with a different number of cyano groups on the low-spin iron(III) precursor has been carried out allowing us to illustrate the influence of the symmetry of the magnetic orbital of the iron center on the magnetic coupling in this heterobimetallic unit. |
BibTeX:
@article{ISI:000277689800047,
author = {Visinescu, Diana and Marilena Toma, Luminita and Cano, Joan and Fabelo, Oscar and Ruiz-Perez, Catalina and Labrador, Ana and Lloret, Francesc and Julve, Miguel},
title = {Magnetic coupling in discrete cyano-bridged Mn-III-Fe-III motifs: Synthesis, crystal structure, magnetic properties and theoretical study},
journal = {DALTON TRANSACTIONS},
year = {2010},
volume = {39},
number = {20},
pages = {5028-5038},
doi = {{10.1039/b926912f}}
}
|
| Visinescu, D., Sutter, J., Ruiz-Perez, C. & Andruh, M. ({2006}), "A new synthetic route towards heterotrimetallic complexes. Synthesis, crystal structure and magnetic properties of a [(CuMnCrIII)-Mn-II-Cr-II] trinuclear complex" , INORGANICA CHIMICA ACTA. , JAN 20, {2006}. Vol. {359} ({2}) , pp. {433-440}. |
| Abstract: The heterotrimetallic complex, [LCuMn(H2O)Cr(phen)(C2O4)(2)](ClO4)center dot H2O (1), has been obtained by assembling heterobinuclear cations, [LCuMn](2+), with [Cr(phen)(C2O4)(2)](-) ions (H2L is the compartmental Schiff-base resulting from the stepwise condensation of 2,6-diformyl-p-cresol with ethylenediamine and diethylenetriamine). The copper(II) and manganese(II) ions are hosted into the compartments of the macrocyclic ligand. [Cr(phen)(C2O4)(2)](-) acts as a ligand, being coordinated through one oxalato oxygen atom to the apical position of the square pyramidal copper(II) ion. The cryomagnetic investigation of 1 reveals an antiferromagnetic interaction between Cu-II and Mn-II within the compartmental ligand (J = -39 cm(-1)). The interaction between Cu-II and Cr-III across the oxalato bridge is negligible. The crystal structure of [LCuPb](ClO4)(2)center dot H2O, a useful precursor in obtaining 3d-3d' complexes, is also reported. (c) 2005 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000234772000006,
author = {Visinescu, D and Sutter, JP and Ruiz-Perez, C and Andruh, M},
title = {A new synthetic route towards heterotrimetallic complexes. Synthesis, crystal structure and magnetic properties of a [(CuMnCrIII)-Mn-II-Cr-II] trinuclear complex},
journal = {INORGANICA CHIMICA ACTA},
year = {2006},
volume = {359},
number = {2},
pages = {433-440},
doi = {{10.1016/j.ica.2005.07.041}}
}
|
| Visinescu, D., Toma, L.M., Fabelo, O., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2009}), "New 3d-4f supramolecular systems constructed by [Fe(bipy)(CN)(4)](-) and partially blocked lanthanide cations" , POLYHEDRON. , MAR 12, {2009}. Vol. {28} ({4}) , pp. {851-859}. |
| Abstract: The reaction of acetonitrile (1-5) and mixed acetonitrile/water 1:1 (6-9) solutions containing the cyanide-bearing [Fe(bipy)(CN)(4)](-) building block (bipy = 2,2'-bipyridine) and the partially blocked [Ln(bpym)](3+) cation (Ln = lanthanide trivalent cation and bpym = 2,2'-bipyrimidine) has afforded two new families of 3d-4f supramolecular assemblies of formula [Ln(bpym)(NO3)(2)(H2O)(3)][Fe(bipy)(CN)(4)] center dot H2O center dot CH3CN [Ln = Sm (1), Gd (2), Tb (3), Dy (4) and Ho (5)] and [Ln(bpym)(NO3)(2)(H2O)(4)][Fe(bipy)(CN)(4)] [Ln = Pr (6), Nd (7), Sm (8), Gd (9)]. They crystallize in the P2(1)/c (1-5) and P2/c (6-9) space groups and their structures are made up of [Fe(bipy)(CN)(4)](-) anions (1-9) and [Ln(bpym)(NO3)(2)(H2O)(n)](+) cations [n = 3 (1-5) and 4 (6-9)] with uncoordinated water and acetonitrile molecules (1-5) which are interlinked through an extensive network of hydrogen bonds and pi-pi stacking into three-dimensional motifs. Both families have in common the occurrence of the low-spin iron(III) unit [Fe(bipy)(CN)(4)](-) where two bipy-nitrogen and four cyanide-carbon atoms build a somewhat distorted octahedral surrounding around the iron atom [Fe-N = 1.980(3)-1.988(3) angstrom (1-5) and 1.988(2)-1.992(2) angstrom (6-9): Fe-C=1.904(5)-1.952(4)angstrom (1-5) and 1.911(2)-1.948(3)angstrom (6-9)]. The main structural difference between both families concerns the environment of the lanthanide atom which is nine-(1-5)/10-coordinated (6-9) with a chelating bpym, two bidentate nitrate and three (1-5)/four (6-9) water molecules building distorted monocapped (1-5)/bicapped (6-9) square antiprisms. This different lanthanide environment is at the origin of the different hydrogen bonding pattern of the two families of compounds. (C) 2008 Elsevier Ltd. All rights reserved. |
BibTeX:
@article{ISI:000264695400029,
author = {Visinescu, Diana and Toma, Luminita M. and Fabelo, Oscar and Ruiz-Perez, Catalina and Lloret, Francesc and Julve, Miguel},
title = {New 3d-4f supramolecular systems constructed by [Fe(bipy)(CN)(4)](-) and partially blocked lanthanide cations},
journal = {POLYHEDRON},
year = {2009},
volume = {28},
number = {4},
pages = {851-859},
doi = {{10.1016/j.poly.2008.12.032}}
}
|
| Visinescu, D., Toma, L.M., Lloret, F., Fabelo, O., Ruiz-Perez, C. & Julve, M. ({2009}), "Unprecedented coexistence of cyano-bridged (Mn4CrIII)-Cr-III and (Mn2CrIII)-Cr-III heterobimetallic complexes in one single crystal" , DALTON TRANSACTIONS. ({1}) , pp. {37-40}. |
| Abstract: The penta-[Mn-III(4-MeO-salen)(H2O)(mu-CN)(4)Cr-III(CN)(2)](+) and trinuclear [Mn-III(4-MeO-salen)(H2O)(mu-CN)(2)CrIII-(CN)(4)](-) units coexist in 1 with weak antiferromagnetic interactions which are overcome by a dc magnetic field of 2.5 T. |
BibTeX:
@article{ISI:000264023700005,
author = {Visinescu, Diana and Toma, Luminita Marilena and Lloret, Francesc and Fabelo, Oscar and Ruiz-Perez, Catalina and Julve, Miguel},
title = {Unprecedented coexistence of cyano-bridged (Mn4CrIII)-Cr-III and (Mn2CrIII)-Cr-III heterobimetallic complexes in one single crystal},
journal = {DALTON TRANSACTIONS},
year = {2009},
number = {1},
pages = {37-40},
doi = {{10.1039/b816412f}}
}
|
| Visinescu, D., Toma, L.M., Lloret, F., Fabelo, O., Ruiz-Perez, C. & Julve, M. ({2008}), "[M-III(bpym)(CN)(4)](-): a suitable building block to design ferrimagnetic cyano-bridged heterobimetallic chains (M = Fe, Cr; bpym=2,2 `-bypyrimidine)" , DALTON TRANSACTIONS. ({31}) , pp. {4103-4105}. |
| Abstract: Two cyano-bridged (MMnIII)-Mn-III [M = Fe (1) and Cr (2)] ferrimagnetic chains are reported; 2 exhibits metamagnetism with two critical fields of 1250 G and 2.0 T which correspond to the overcoming by the applied dc field of the inter- and intrachain magnetic interactions, respectively. |
BibTeX:
@article{ISI:000258083800005,
author = {Visinescu, Diana and Toma, Luminita Marilena and Lloret, Francesc and Fabelo, Oscar and Ruiz-Perez, Catalina and Julve, Miguel},
title = {[M-III(bpym)(CN)(4)](-): a suitable building block to design ferrimagnetic cyano-bridged heterobimetallic chains (M = Fe, Cr; bpym=2,2 `-bypyrimidine)},
journal = {DALTON TRANSACTIONS},
year = {2008},
number = {31},
pages = {4103-4105},
doi = {{10.1039/b809160a}}
}
|
| Yanes, A.C., Del-Castillo, J., Mendez-Ramos, J., Rodriguez, V.D., Torres, M.E. & Arbiol, J. ({2007}), "Luminescence and structural characterization of transparent nanostructured Eu3+-doped LaF3-SiO2 glass-ceramics prepared by sol-gel method" , OPTICAL MATERIALS. , APR, {2007}. Vol. {29} ({8}) , pp. {999-1003}. |
| Abstract: Glass-ceramics with composition of 89.9SiO(2)-10LaF(3)-0.1EuF(3) (mol were prepared by sol-gel method. LaF3 nanocrystals, precipitated by heat-treatments, were identified by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Besides the well-known red emission of Eu3+ ions, higher energy emissions coming from upper-lying levels D-5(1) and D-5(2) can be observed at room temperature due to the very low phonon energies of the LaF3 matrix. Moreover, from site selective excitation and emission spectra in the temperature range from 13 to 300 K, it is concluded that the fraction of Eu3+ ions partitioned into LaF3 nanocrystals, substituting La (3+) ions, is comparable to the one staying in the SiO2 glassy phase. (c) 2006 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000245847200015,
author = {Yanes, A. C. and Del-Castillo, J. and Mendez-Ramos, J. and Rodriguez, V. D. and Torres, M. E. and Arbiol, J.},
title = {Luminescence and structural characterization of transparent nanostructured Eu3+-doped LaF3-SiO2 glass-ceramics prepared by sol-gel method},
journal = {OPTICAL MATERIALS},
year = {2007},
volume = {29},
number = {8},
pages = {999-1003},
doi = {{10.1016/j.optmat.2006.02.021}}
}
|
| Yanes, A.C., Mendez-Ramos, J., del Castillo, J., Velazquez, J.J. & Rodriguez, V.D. ({2010}), "Size-dependent luminescence of Sm3+ doped SnO2 nano-particles dispersed in sol-gel silica glass" , APPLIED PHYSICS B-LASERS AND OPTICS. , DEC, {2010}. Vol. {101} ({4}) , pp. {849-854}. |
| Abstract: Sol-gel glasses with composition (100-x)SiO2-xSnO(2) doped with 0.4 mol% of Sm3+, with x ranging from 1 to 10, have been successfully synthesized. Transparent doped nano-glass-ceramics were prepared by thermal treatment of the precursor glasses at 900A degrees C during 4 hours, leading to nanocomposites comprising SnO2 nanocrystals embedded into an amorphous SiO2 phase. A structural analysis in terms of X-ray Diffraction and High Resolution Transmission Electron Microscopy confirms the precipitation of SnO2 nanocrystals within the glassy matrix. The mean radius of the obtained SnO2 nanocrystals, ranging from 2.1 to 4.7 nm calculated by the Scherrer and Brus equations, similar to the Bohr's exciton radius, constitutes a wide band-gap semiconductor quantum-dot system. Energy transfer from SnO2 nanocrystal host to Sm3+ ions is confirmed by luminescence spectra and analyzed as a function of SnO2 concentration, showing an evolution that could be ascribed to selective excitation of nanocrystal sets with predetermined size. Besides, a study of the luminescence as a function of temperature helps to clarify the involved energy transfer mechanisms. |
BibTeX:
@article{ISI:000284771400018,
author = {Yanes, A. C. and Mendez-Ramos, J. and del-Castillo, J. and Velazquez, J. J. and Rodriguez, V. D.},
title = {Size-dependent luminescence of Sm3+ doped SnO2 nano-particles dispersed in sol-gel silica glass},
journal = {APPLIED PHYSICS B-LASERS AND OPTICS},
year = {2010},
volume = {101},
number = {4},
pages = {849-854},
doi = {{10.1007/s00340-010-4331-0}}
}
|
| Yanes, A.C., Santana-Alonso, A., Mendez-Ramos, J., del Castillo, J. & Rodriguez, V.D. ({2009}), "Yb3+-Er3+ co-doped sol-gel transparent nano-glass-ceramics containing NaYF4 nanocrystals for tuneable up-conversion phosphors" , JOURNAL OF ALLOYS AND COMPOUNDS. , JUL 8, {2009}. Vol. {480} ({2}) , pp. {706-710}. |
| Abstract: Transparent nano-glass-ceramics containing Yb3+-Er3+ co-doped NaYF4 nanocrystals have been successfully developed for the first time by thermal treatment of precursor bulk glasses obtained by sol-gel technique. Precipitation of NaYF4 nanocrystals has been confirmed by X-ray diffraction measurements and their sizes have been determined by Scherrer's equation. Luminescence measurements confirm the partition of rare-earth ions in NaYF4 nanocrystals. Visible up-conversion luminescence has been obtained under infrared excitation at 980 nm. Up-conversion mechanisms have been discussed and the ratio between red and green up-conversion emission bands can be varied as a function of temperature of heat treatment and pump power resulting in colour tuneable up-conversion phosphors with applications in optical integrated devices. Colour tuneability has been also analyzed and quantified in terms of CIE standard chromaticity diagram. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000267798600113,
author = {Yanes, A. C. and Santana-Alonso, A. and Mendez-Ramos, J. and del-Castillo, J. and Rodriguez, V. D.},
title = {Yb3+-Er3+ co-doped sol-gel transparent nano-glass-ceramics containing NaYF4 nanocrystals for tuneable up-conversion phosphors},
journal = {JOURNAL OF ALLOYS AND COMPOUNDS},
year = {2009},
volume = {480},
number = {2},
pages = {706-710},
doi = {{10.1016/j.jallcom.2009.02.019}}
}
|
| Yanes, A.C., Velazquez, J.J., del Castillo, J., Mendez-Ramos, J. & Rodriguez, V.D. ({2009}), "Colour tuneability and white light generation in Yb3+-Ho3+-Tm3+ co-doped SiO2-LaF3 nano-glass-ceramics prepared by sol-gel method" , JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY. , JUL, {2009}. Vol. {51} ({1}) , pp. {4-9}. |
| Abstract: Nanostructured transparent glass-ceramics with composition of 95SiO(2)-5LaF(3) co-doped with 0.3Yb(3+), 0.1Ho(3+) and 0.1Tm(3+) (mol were synthesized by thermal treatment of precursor sol-gel derived glasses. X-ray diffraction and transmission electron microscopy analysis point out the precipitation of hexagonal LaF3 nanocrystals with diameter ranging from 11 to 20 nm in these nano-glass-ceramics. White light generation by means of efficient blue, green and red up-conversion luminescence under infrared excitation at 980 nm was observed and involved mechanisms were analyzed. Colour tuneability is achieved by varying the up-conversion emission ratios as a function of pump power. |
BibTeX:
@article{ISI:000266482900002,
author = {Yanes, A. C. and Velazquez, J. J. and del-Castillo, J. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Colour tuneability and white light generation in Yb3+-Ho3+-Tm3+ co-doped SiO2-LaF3 nano-glass-ceramics prepared by sol-gel method},
journal = {JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY},
year = {2009},
volume = {51},
number = {1},
pages = {4-9},
doi = {{10.1007/s10971-009-1924-3}}
}
|
| Yanes, A.C., Velazquez, J.J., del Castillo, J., Mendez-Ramos, J. & Rodriguez, V.D. ({2008}), "Site-selective spectroscopy in Sm3+-doped sol-gel-derived nano-glass-ceramics containing SnO2 quantum dots" , NANOTECHNOLOGY. , JUL 23, {2008}. Vol. {19} ({29}) |
| Abstract: Nano-glass-ceramics of composition 95SiO(2)-5SnO(2) doped with 0.4 Sm3+ (mol were synthesized by the thermal treatment of precursor sol-gel glasses. Structural and luminescence measurements were carried out. The precipitated SnO2 nanocrystals in the glass matrix constitute a wide bandgap quantum-dot system with size comparable to the bulk exciton Bohr radius. A site-selective excitation, by energy transfer from the semiconductor host, reveals that a fraction of the Sm3+ ions are incorporated in the SnO2 nanocrystals, whereas the rest remains in the silica glassy phase. An evolution in the Sm3+ emission spectra has been observed when the SnO2 nanocrystals are excited with different UV wavelengths, which has been ascribed to selective excitation of nanocrystal sets with predetermined size. |
BibTeX:
@article{ISI:000256838300020,
author = {Yanes, A. C. and Velazquez, J. J. and del-Castillo, J. and Mendez-Ramos, J. and Rodriguez, V. D.},
title = {Site-selective spectroscopy in Sm3+-doped sol-gel-derived nano-glass-ceramics containing SnO2 quantum dots},
journal = {NANOTECHNOLOGY},
year = {2008},
volume = {19},
number = {29},
doi = {{10.1088/0957-4484/19/29/295707}}
}
|
| Yuste, C., Armentano, D., Marino, N., Canadillas-Delgado, L., Delgado, F.S., Ruiz-Perez, C., Rillema, D.P., Lloret, F. & Julve, M. ({2008}), "Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes" , DALTON TRANSACTIONS. ({12}) , pp. {1583-1596}. |
| Abstract: The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu-4(bpz)(4)(tcm)(8)] (3), [Cu(terpy)(tcm)]center dot tcm(n) (4) and [Cu-2(tppz)(tcm)(4)]center dot 3/2H(2)O(n) (5) [pyim= 2-(2-pyridyl) imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2 `'-terpyridine and tppz = 2,3,5,6-tetrakis( 2-pyridyl) pyrazine] are reported. Complexes 1, 2 and 4 are uniform copper(II) chains with single-(1 and 4) and double-(2) mu-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) angstrom (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1, 2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine) copper(II) units at the corners, the edges being built by single-and double-mu-1,5-tcm bridges with copper -copper separations of 7.969(1) and 7.270(1) angstrom, respectively. Five-and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in 3. Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double mu-1,5-tcm bridges, the intrachain copper -copper distances being 6.549(7) and 7.668(1) angstrom, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1 -5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- [J = +0.11(1) cm(-1) (2)] and antiferromagnetic interactions [J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3)] across the mu-1,5-tcm bridges and intermediate antiferromagnetic coupling [-J = 37.4(1) cm(-1) (5)] through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems. |
BibTeX:
@article{ISI:000253908900010,
author = {Yuste, C. and Armentano, D. and Marino, N. and Canadillas-Delgado, L. and Delgado, F. S. and Ruiz-Perez, C. and Rillema, D. P. and Lloret, F. and Julve, M.},
title = {Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing copper(II) complexes},
journal = {DALTON TRANSACTIONS},
year = {2008},
number = {12},
pages = {1583-1596},
doi = {{10.1039/b717347d}}
}
|
| Yuste, C., Canadillas-Delgado, L., Ruiz-Perez, C., Lloret, F. & Julve, M. ({2010}), "Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(II) complexes: preparation, X-ray structure and magnetic properties" , DALTON TRANSACTIONS. Vol. {39} ({1}) , pp. {167-179}. |
| Abstract: The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu-2(tppz)(H2O)(2)(CF3SO3)(4)] (1), [Cu(tppz)(CrO4)](n)center dot 3nH(2)O (2) and [Cu-4(tppz)(4)(H2O)(4)(MoO4)(2)](CF3SO3)(4)center dot 7H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl) pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO4), the value of the intrachain metal-metal separation being 4.2614(5) angstrom. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H2O)](2+) units are connected through two molybdate groups, each one adopting the m1,1,2-MoO4 bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN3O2 and elongated octahedral CuN3O3 surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) angstrom [Cu(2)center dot center dot center dot Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) angstrom. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro-[J = -48.0(1) cm(-1) with (H) over cap = -J (S) over cap (1)center dot(S) over cap (2) (1)], weak ferro- [J = +0.28(1) cm(-1) with (H) over cap = -J Sigma(i) (S) over cap (i)center dot(S) over cap (i) + I (2)] and coexistence of weak ferro-and antiferromagnetic interactions [J(1) = + 2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with (H) over cap = -J(1) ((S) over cap (2)center dot(S) over cap (3)) + J(2) ((S) over cap (1)center dot(S) over cap (3) + (S) over cap (2)center dot(S) over cap (4)) + J(3) ((S) over cap (1)center dot(S) over cap (2) + (S) over cap (3)center dot(S) over cap (4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO4 (2), di-mu(1,1)-MoO4 and mu(1,2)-MoO4 (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent ystems. |
BibTeX:
@article{ISI:000272679300022,
author = {Yuste, Consuelo and Canadillas-Delgado, Laura and Ruiz-Perez, Catalina and Lloret, Francesc and Julve, Miguel},
title = {Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(II) complexes: preparation, X-ray structure and magnetic properties},
journal = {DALTON TRANSACTIONS},
year = {2010},
volume = {39},
number = {1},
pages = {167-179},
doi = {{10.1039/b913274k}}
}
|
| Yuste, C., Ferrando-Soria, J., Cangussu, D., Fabelo, O., Ruiz-Perez, C., Marino, N., De Munno, G., Stiriba, S.-E., Ruiz-Garcia, R., Cano, J., Lloret, F. & Julve, M. ({2010}), "Topological control of the spin coupling in dinuclear copper(II) complexes with meta- and para-phenylenediamine bridging ligands" , INORGANICA CHIMICA ACTA. , JUN 10, {2010}. Vol. {363} ({9}) , pp. {1984-1994}. |
| Abstract: A novel series of copper(II) complexes of formula [Cu(tren)(mpda)](ClO4)(2)center dot 1/2H(2)O (1), [Cu-2(tren)(2)(mpda)](ClO4)(4)center dot 2H(2)O (2), and [Cu-2(tren)(2)(ppda)](ClO4)(4)center dot 2H(2)O (3) containing the tetradentate tris(2-amino-ethyl)amine (tren) terminal ligand and the potentially bridging 1,n-phenylenediamine [n = 3 (mpda) and 4 (ppda)] ligand have been prepared and spectroscopically characterized. X-ray diffraction on single crystals of 1 and 3 show the presence of mono-(1) and dinuclear (3) copper(II) units where the mpda (1) and ppda (3) ligands adopt terminal monodentate (1) and bridging bis(monodentate) (3) coordination modes toward [Cu(tren)](2+) cations with an overall non-planar, orthogonal disposition of the phenylene group and the N-Cu-N threefold axis of the trigonal bipyramid of each copper(II) ion [values of the Cu-N-CC torsion angle (phi) in the range of 50.8(3)-79.2(2) (1) and 80.9(2)-86.5(2)degrees (3)]. Variable-temperature magnetic susceptibility measurements on the dinuclear complexes 2 and 3 show the occurrence of moderate ferromagnetic (J = +8.3 cm(-1), 2) and strong antiferromagnetic (J = -51.4 cm(-1), 3) couplings between the two copper(II) ions across the meta-and para-phenylenediamine bridges, leading to S = 1 (2) and S = 0 (3) ground spin states [H = -JS(1)center dot S-2 with S-1 = S-2 = S-Cu = 1/2]. Density functional theory (DFT) calculations on the triplet (2) and broken-symmetry (BS) singlet (3) ground spin states, support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction through the predominantly p-type orbital pathway of the 1, n-phenylenediamine bridge. Finally, a new magneto-structural correlation between the magnitude of the magnetic coupling (J) and the Cu-N-C-C torsion angle (phi) has been found which reveals the role of sigma- versus pi-type orbital pathways in the modulation of the magnetic coupling for m-and p-phenylenediamine-bridged dicopper(II) complexes. (C) 2009 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000277934700008,
author = {Yuste, Consuelo and Ferrando-Soria, Jesus and Cangussu, Danielle and Fabelo, Oscar and Ruiz-Perez, Catalina and Marino, Nadia and De Munno, Giovanni and Stiriba, Salah-Eddine and Ruiz-Garcia, Rafael and Cano, Joan and Lloret, Francesc and Julve, Miguel},
title = {Topological control of the spin coupling in dinuclear copper(II) complexes with meta- and para-phenylenediamine bridging ligands},
journal = {INORGANICA CHIMICA ACTA},
year = {2010},
volume = {363},
number = {9},
pages = {1984-1994},
doi = {{10.1016/j.ica.2009.03.001}}
}
|
| Zambelli, M., Abril, M., Lavin, V., Speghini, A. & Bettinelli, M. ({2004}), "Fluorescence line narrowing spectroscopy of Eu3+ in a niobium tellurite glass" , JOURNAL OF NON-CRYSTALLINE SOLIDS. , OCT 15, {2004}. Vol. {345} , pp. {386-390}. Note:10th International Conference on the Physics of Non-Crystalline Solids (PNCS), Parma, ITALY, JUL 13-17, 2003. |
| Abstract: The relationship between optical properties and local structure has been studied in a niobium tellurite glass of molar composition 4.0Nb(2)O(5)-87.0TeO(2)-8.5Al(2)O(3)-0.5Eu(2)O(3) using both broadband and laser-induced fluorescence line narrowing techniques. From the broad band excitation and emission spectra information about the local symmetry and the main lanthanide-ligand vibrational modes of the Eu3+ ions in this matrix was obtained. Under laser selective excitation in the F-7(0)-->D-5(0) inhomogeneous band the site-dependent luminescence of the Eu3+ ions allow us to analyze the distribution of local environments for the lanthanide ion in the nobium tellurite glass. Moreover, the energies of the Stark components of the F-7(1) and F-7(2) multiplets were obtained as a function of the excitation energy and a crystal field analysis was carried out assuming a C-2v site symmetry. From the calculated crystal field parameters B-kq the ratios B-22/B-20 and B-44/B-40 for each excitation energy were obtained and compared with the values calculated using the geometric model proposed by Brecher and Riseberg. (C) 2004 Elsevier B.V. All rights reserved. |
BibTeX:
@article{ISI:000225583200075,
author = {Zambelli, M and Abril, M and Lavin, V and Speghini, A and Bettinelli, M},
title = {Fluorescence line narrowing spectroscopy of Eu3+ in a niobium tellurite glass},
journal = {JOURNAL OF NON-CRYSTALLINE SOLIDS},
year = {2004},
volume = {345},
pages = {386-390},
note = {10th International Conference on the Physics of Non-Crystalline Solids (PNCS), Parma, ITALY, JUL 13-17, 2003},
doi = {{10.1016/j.jnoncrysol.2004.08.049}}
}
|
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