Artículos SCI
2020
2020
Nanotecnología en Superficies y Plasma
Optofluidic liquid sensing on electromicrofluidic devices
Oliva-Ramirez, M; Wang, SL; Rico-Gavira, V; Lopez-Santos, C; Fan, SK; Gonzalez-Elipe, ARMaterials Research Express, 7 (2020) 036407
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Electromicrofluidic (EMF) devices are used to handle and move tiny amounts of liquids by electrical actuation, including electrowetting-on-dielectric (EWOD) and dielectrophoresis (DEP). Monitoring the liquid characteristics in one of these devices requires suitable sensing transducers incorporated within the microfluidic structure. In the present work, we describe the incorporation of an optofluidic photonic transducer in an EMF device to monitor the refractive index of a liquid during its manipulation. The incorporated transducer consists of a responsive porous Bragg Microcavity (BM) deposited via physical vapor oblique angle deposition. Besides reporting the manufacturing procedure of the sensing-EMF device combining liquid handling and monitoring, the performance of the BM is verified by infiltrating several liquids dripped on its surface and comparing the responses with those of liquid droplets electrically moved from the delivery part of the chip to the BM location. This study proved that modified EMF devices can incorporate photonic structures to analyze very low liquid volumes (similar to 0.2 mu L) during its handling.
Marzo, 2020 | DOI: 10.1088/2053-1591/ab7fdf
Materiales Ópticos Multifuncionales
Localized surface plasmon effects on the photophysics of perovskite thin films embedding metal nanoparticles
Bayles, A; Carretero-Palacios, S; Calio, L; Lozano, G; Calvo, ME; Miguez, HJournal of Materials Chemistry C, 8 (2020) 916-921
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Herein we provide direct experimental evidence that proves that the photophysical properties of thin methylammonium lead iodide perovskite films are significantly enhanced by localized surface plasmon resonances (SPRs). Observations are well supported by rigorous calculations that prove that improved light harvesting can be unequivocally attributed to plasmonic scattering and near field reinforcement effects around silver nanoparticles embedded within the semiconductor layer. Adequate design of the localized SPR allows raising the absorptance of a 300 nm thick film at well-defined spectral regions while minimizing the parasitic absorption from the metallic inclusions. Measured enhancements can be as large as 80% at specific wavelengths and 20% when integrated over the whole range at which SPR occurs, in agreement with theoretical estimations. Simultaneously, the characteristic quenching effect that the vicinity of metals has on the photoluminescence of semiconductors is largely compensated for by the combined effect of the enhanced photoexcitation and the higher local density of photon states occurring at SPR frequencies, with a two fold increase of the perovskite photoemission efficiency being measured.
Marzo, 2020 | DOI: 10.1039/c9tc05785d
Fotocatálisis Heterogénea: Aplicaciones
Preparation of ZnFe2O4/ZnO composite: Effect of operational parameters for photocatalytic degradation of dyes under UV and visible illumination
Zouhier, M.; Tanji, K.; Navio, J.A.; Hidalgo, M.C.; Jaramillo-Páez, C.; Kherbeche, A.Journal of Photochemistry and Photobiology A: Chemistry, 390 (2020) 112305
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An ZnFe2O4/ZnO composite catalyst was prepared by solution combustion method. In this study, one nominal molar percentage of iron was used in the synthesis, corresponding to 20 % molar relative to ZnO. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray Fluorescence (XRF), Scanning Electronic Microscopy (SEM), Transmission Electronic Microscopy (TEM) and Ultraviolet-visible (UV–vis) diffuse spectroscopy (DRS). The photocatalytic activities of the catalysts were investigated based on the degradation of two dyes, methylene blue (MB) and remazol brilliant blue (RBB), in aqueous solution under both UV and visible light illumination respectively. It was found that the composite had a good photocatalytic activity at basic pH by using 1 g/L of catalyst under UV illumination for both MB and RBB. Under visible illumination, while pristine ZnO showed no activity, the composite exhibited an excellent visible efficiency, reaching up to an 80 % conversion of the initial dye concentrations in 2 h. The enhancement of the visible photocatalytic activity of Fe/ZnO sample with respect to pristine ZnO is attributed to the formation of ZnFe2O4 coupled with ZnO, having a narrow band gap value that contributes to the absorption of visible photons with an improved separation path for the photo-generated carriers.
Marzo, 2020 | DOI: 10.1016/j.jphotochem.2019.112305
Química de Superficies y Catálisis
Catalytic Performance of Bulk and Al2O3-Supported Molybdenum Oxide for the Production of Biodiesel from Oil with High Free Fatty Acids Content
Navajas, A; Reyero, I; Jimenez-Barrera, E; Romero-Sarria, F; Llorca, J; Gandia, LMCatalysts, 10 (2020) 158
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Non-edible vegetable oils are characterized by high contents of free fatty acids (FFAs) that prevent from using the conventional basic catalysts for the production of biodiesel. In this work, solid acid catalysts are used for the simultaneous esterification and transesterification with methanol of the FFAs and triglycerides contained in sunflower oil acidified with oleic acid. Molybdenum oxide (MoO3), which has been seldom considered as a catalyst for the production of biodiesel, was used in bulk and alumina-supported forms. Results showed that bulk MoO3 is very active for both transesterification and esterification reactions, but it suffered from severe molybdenum leaching in the reaction medium. When supported on Al2O3, the MoO3 performance improved in terms of active phase utilization and stability though molybdenum leaching remained significant. The improvement of catalytic performance was ascribed to the establishment of MoO3-Al2O3 interactions that favored the anchorage of molybdenum to the support and the formation of new strong acidic centers, although this effect was offset by a decrease of specific surface area. It is concluded that the development of stable catalysts based on MoO3 offers an attractive route for the valorization of oils with high FFAs content.
Febrero, 2020 | DOI: 10.3390/catal10020158
Reactividad de Sólidos
Synthesis of Mn2+-doped ZnS by a mechanically induced self-sustaining reaction
Aviles, MA; Cordoba, JM; Sayagues, MJ; Gotor, FJJournal of Materials Science, 55 (2020) 1603-1613
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The mechanochemical process denoted as a mechanically induced self-sustaining reaction was successfully applied in obtaining Mn-doped ZnS samples with Mn content between 0 and 5 mol%. The process consists in milling Zn/Mn/S powder elemental mixtures with the appropriate stoichiometry, which promotes after approximately 80 min the induction of a combustion reaction. The doping level was properly adjusted by controlling the atomic ratio of the starting mixture. A complete characterization of samples was carried out, including X-ray diffraction, high-resolution transmission electron microscopy, selected area electron diffraction, energy-dispersive X-ray spectroscopy, Raman spectroscopy, diffuse reflectance UV-Vis spectroscopy and emission and excitation photoluminescence measurements. A wurtzite structure, in which Mn2+ replaces Zn2+, was obtained with a nanometric character. The photoluminescence of samples showed the characteristic (Mn2+T1)-T-4-(6)A(1) emission that was highly dependent on the doping level. The maximum luminescence efficiency through the ZnS excitation was found for a doping value of 1 mol%. The photoluminescence showed virtually no contribution from the host emission, which confirmed that samples were properly doped.
Febrero, 2020 | DOI: 10.1007/s10853-019-04138-8
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