Scientific Papers in SCI
2023
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, HNanoscale, 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, LMaterials, 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
Reactividad de Sólidos
Nanocrystalline Skinnerite (Cu3SbS3) Prepared by High-Energy Milling in a Laboratory and an Industrial Mill and Its Optical and Optoelectrical Properties
Dutkova, E; Sayagues, MJ; Fabian, M; Balaz, M; Kovac, J; Kovac, J; Stahorsky, M; Achimovicova, M; Bujnakova, ZLMolecules, 28 (2023) 1
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Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu3SbS3) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu3SbS4; 15%), and tetrahedrite (Cu11.4Sb4S13; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu3SbS3 prepared in the laboratory mill was determined to be 1.7 eV with UV-Vis spectroscopy. Photocurrent responses verified with I-V measurements under dark and light illumination and Cu3SbS3 nanocrystals showed similar to 45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu3SbS3) prepared via laboratory milling are interesting for photovoltaic applications.
January, 2023 | DOI: 10.3390/molecules28010326
Química de Superficies y Catálisis
Formic Acid Dehydrogenation over Ru- and Pd-Based Catalysts: Gas- vs. Liquid-Phase Reactions
Ruiz-Lopez, E; Pelaez, MR; Ruz, MB; Leal, MID; Tejada, MM; Ivanova, S; Centeno, MAMaterials, 16 (2023) 472
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Formic acid has recently been revealed to be an excellent hydrogen carrier, and interest in the development of efficient and selective catalysts towards its dehydrogenation has grown. This reaction has been widely explored using homogeneous catalysts; however, from a practical and scalable point of view, heterogeneous catalysts are usually preferred in industry. In this work, formic acid dehydrogenation reactions in both liquid- and vapor-phase conditions have been investigated using heterogeneous catalysts based on mono- or bimetallic Pd/Ru. In all of the explored conditions, the catalysts showed good catalytic activity and selectivity towards the dehydrogenation reaction, avoiding the formation of undesired CO.
January, 2023 | DOI: 10.3390/ma16020472
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Methanation of CO2 over High Surface Nickel/Aluminates Compounds Prepared by a Self-Generated Carbon Template
Roudane, S; Bettahar, N; Caballero, A; Holgado, JPCatalysts, 13 (2023) 142
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Catalytic gas-phase hydrogenation of CO2 into CH4 was tested under three different nickel/aluminate catalysts obtained from precursors of hexaaluminate composition (MAl16O19, M = Mg, Ca, Ba). These catalysts were prepared using a carbon template method, where carbon is self-generated from a sol-gel that contains an excess of citric acid and the Al and M salts (Ba2+, Ca2+, Mg2+) by two-step calcination in an inert/oxidizing atmosphere. This procedure yielded Ni particles decorating the surface of a porous high surface area matrix, which presents a typical XRD pattern of aluminate structure. Ni particles are obtained with a homogeneous distribution over the surface and an average diameter of ca 25-30 nm. Obtained materials exhibit a high conversion of CO2 below 500 degrees C, yielding CH4 as a final product with selectivity >95%. The observed trend with the alkaline earth cation follows the order NiBaAlO-PRx > NiCaAlO-PRx > NiMgAlO-PRx. We propose that the high performance of the NiBaAlO sample is derived from both an appropriate distribution of Ni particle size and the presence of BaCO3, acting as a CO2 buffer in the process.
January, 2023 | DOI: 10.3390/catal13010142
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