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Scientific Papers in SCI



2023


Materiales Ópticos Multifuncionales

Determination of the optical constants of ligand-free organic lead halide perovskite quantum dots

Rubino, A; Lozano, G; Calvo, ME; Miguez, H
Nanoscale, 15 (2023) 2553-2560

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Precise knowledge of the optical constants of perovskite lead halide quantum dots (QDs) is required to both understand their interaction with light and to rationally design and optimize the devices based on them. However, their determination from colloidal nanocrystal suspensions, or films made out of them, remains elusive, as a result of the difficulty in disentangling the optical constants of the organic capping ligands and those of the semiconductor itself. In this work, we extract the refractive index and extinction coefficient of ligand-free methylammonium lead iodide (MAPbI(3)) and bromide (MAPbBr(3)) nanocrystals. In order to prevent the use of organic ligands in the preparation, we follow a scaffold assisted synthetic procedure, which yields a composite film of high optical quality that can be independently and precisely characterized and modelled. In this way, the contribution of the guest nanocrystals can be successfully discriminated from that of the host matrix. Using a Kramers-Kronig consistent dispersion model along with an effective medium approximation, it is possible to derive the optical constants of the QDs by fitting the spectral dependence of light transmitted and reflected at different angles and polarizations. Our results indicate a strong dependence of the optical constants on the QD size. Small nanocrystals show remarkably large values of the extinction coefficient compared to their bulk counterparts. This analysis opens the door to the rigorous modelling of solar cells and light-emitting diodes with active layers based on perovskite QDs.


February, 2023 | DOI: 10.1039/d2nr05109e

Materiales Avanzados

Effect of L-Glutamic Acid on the Composition and Morphology of Nanostructured Calcium Phosphate as Biomaterial

Takabait, F; Martinez-Martinez, S; Mahtout, L; Graba, Z; Sanchez-Soto, PJ; Perez-Villarejo, L
Materials, 16 (2023) 1262

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Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H(2)G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was similar to 1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4-] and [CaHG(+)]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.


February, 2023 | DOI: 10.3390/ma16031262

Materiales Coloidales

Europium doped-double sodium bismuth molybdate nanoparticles as contrast agents for luminescence bioimaging and X-ray computed tomography

Calderon-Olvera, RM; Nunez, NO; Gonzalez-Mancebo, D; Monje-Moreno, JM; Munoz-Rui, MJ; Gomez-Gonzalez, E; Arroyo, E; Torres-Herrero, B; De la Fuente, JM; Ocaña, M
Inorganic Chemistry Frontiers, 10(11) (2023) 3202

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A one-pot method for the synthesis of uniform Eu3+-doped NaBi(MoO4)2 nanoparticles with an ellipsoidal shape and tetragonal crystal structure functionalized with polyacrylic acid is reported for the first time in the literature. The method is based on a homogeneous precipitation reaction from solutions in an ethylene glycol/water medium containing appropriate bismuth, sodium, and molybdate precursors and polyacrylic acid. The luminescence properties (excitation and emission spectra and luminescence lifetime) of such nanoparticles are evaluated for different Eu3+ doping levels, finding an intense red emission for all synthesized samples. The X-ray attenuation properties of the nanoparticles have been also analyzed, which were found to be better than those of a commercially computed tomography contrast agent (iohexol). The dispersibility of the nanoparticles in a physiological medium was also analyzed, finding that they could be well dispersed in a 2-N-morpholinoethanesulfonic acid monohydrate medium (pH = 6.5). Finally, the cell viability of such a phosphor has been analyzed using MIA-PaCa-2 cells and its in vivo toxicity has been evaluated using the nematode Caenorhabditis elegans model finding no significant toxicity in both cases up to a nanoparticle concentration of 100 μg mL−1, which is within the range required for most in vivo applications. The developed Eu3+-doped NaBi(MoO4)2 nanoparticles are, therefore, excellent candidates for their use as bimodal probes for luminescence imaging and X-ray computed tomography.


February, 2023 | DOI: 10.1039/D2QI02664C

Reactividad de Sólidos

Determination of the activation energy under isothermal conditions: revisited

Arcenegui-Troya, J; Sanchez-Jimenez, PE; Perejon, A; Perez-Maqueda, LA
Journal of Thermal Analysis and Calorimetry, 148 (2023) 1679-1686

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The kinetic analysis of solid-state processes aims at obtaining fundamental information that can be used for predicting the time evolution of a process within a wide range of conditions. It is an extended belief that the determination of the kinetic parameters from the analysis of curves recorded under isothermal conditions is strongly conditioned by the kinetic model used to fit the experimental data. Thus, much effort is devoted to finding the model that truly describes a process in order to calculate the kinetic parameters with accuracy. In this work, we demonstrate that the value of activation energy determined from kinetic analysis of isothermal curves is independent of the kinetic model used to fit the experimental data and, taking advantage of the underlying reason for this, a method for determining the activation energy with two isothermal curves is proposed.


February, 2023 | DOI: 10.1007/s10973-022-11728-3

Nanotecnología en Superficies y Plasma

Incorporation of a Metal Catalyst for the Ammonia Synthesis in a Ferroelectric Packed-Bed Plasma Reactor: Does It Really Matter?

Navascues, P; Garrido-Garcia, J; Cotrino, J; Gonzalez-Elipe, AR; Gomez-Ramirez, A
ACS Sustainable Chemistry & Engineering, 11 (2023) 3621-3632

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Plasma-catalysis has been proposed as a potential alternative for the synthesis of ammonia. Studies in this area focus on the reaction mechanisms and the apparent synergy existing between processes occurring in the plasma phase and on the surface of the catalytic material. In the present study, we approach this problem using a parallel-plate packed-bed reactor with the gap between the electrodes filled with pellets of lead zirconate titanate (PZT), with this ferroelectric material modified with a coating layer of alumina (i.e., Al2O3/PZT) and the same alumina layer incorporating ruthenium nanoparticles (i.e., Ru-Al2O3/PZT). At ambient temperature, the electrical behavior of the ferroelectric packed-bed reactor differed for these three types of barriers, with the plasma current reaching a maximum when using Ru-Al2O3/PZT pellets. A systematic analysis of the reaction yield and energy efficiency for the ammonia synthesis reaction, at ambient temperature and at 190 °C and various electrical operating conditions, has demonstrated that the yield and the energy efficiency for the ammonia synthesis do not significantly improve when including ruthenium particles, even at temperatures at which an incipient catalytic activity could be inferred. Besides disregarding a net plasma-catalysis effect, reaction results highlight the positive role of the ferroelectric PZT as moderator of the discharge, that of Ru particles as plasma hot points, and that of the Al2O3 coating as a plasma cooling dielectric layer.


February, 2023 | DOI: 10.1021/acssuschemeng.2c05877

 

 

 

 

 

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