Evaluación y Análisis de la Calidad en Prácticas de Laboratorio de Química Inorgánica

Formato artículo para difundir los resultados del proyecto de innovación UCA - AAA_14_059, titulado "EVALUACIÓN Y MEJORA DE LAS PRÁCTICAS DE TALLER Y LABORATORIO DE LAS ÁREAS DE CONOCIMIENTO DE CIENCIA DE LOS MATERIALES E INGENIERÍA METALÚRGICA Y DE QUÍMICA INORGÁNICA".Después de haberse implantado el Grado en Química en la Facultad de Ciencias de la Universidad de Cádiz, el Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica ha llevado a cabo la evaluación de las prácticas de taller y laboratorio de las asignaturas que imparte. Para ello se han desarrollado una serie de cuestionarios dirigidos tanto a los alumnos como a los profesores encargados de impartir las asignaturas. A partir de los resultados ha sido posible realizar un análisis en profundidad de cada asignatura con el fin de contrastar la opinión de alumnos y profesores y evaluar si son necesarias determinadas modificaciones o incluir algunas mejoras que faciliten a los alumnos el normal desarrollo de las prácticas

Structural modulation and direct measurement of subnanometric bimetallic PtSn clusters confined in zeolites

[EN] Modulating the structures of subnanometric metal clusters at the atomic level is a great synthetic and characterization challenge in catalysis. Here, we show how the catalytic properties of subnanometric platinum clusters (0.5-0.6 nm) confined in the sinusoidal 10R channels of purely siliceous MFI zeolite are modulated upon introduction of partially reduced tin species that interact with the noble metal at the metal/support interface. The platinum-tin clusters are stable in H(2)over an extended period of time (>6 h), even at high temperatures (for example, 600 degrees C), which is determined by only a few additional tin atoms added to the platinum clusters. The structural features of platinum-tin clusters, which are not immediately visible by conventional characterization techniques but can be established after combination of in situ extended X-ray absorption fine structure, high-angle annular dark-field scanning transmission electron microscopy and CO infrared data, are key to providing a one-order of magnitude lower deactivation rate in the propane dehydrogenation reaction while maintaining high intrinsic (initial) catalytic activityThis work was supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (SEV-2016-0683). L.L. thanks the ITQ for providing a contract. The authors also thank the Microscopy Service of the UPV for the TEM and STEM measurements. The XAS measurements were carried out in the CLAESS beamline of the ALBA synchrotron. We thank Giovanni Agostini for his kind support in the analysis of XAS data. HR-HAADF-STEM measurements were performed at DME-UCA at Cadiz University with financial support from FEDER/MINECO (MAT2017-87579-R and MAT2016-81118-P). C.W.L. thanks CAPES (Science without Frontiers -Process no. 13191/13-6) for a predoctoral fellowship. The financial support from ExxonMobil for this project is also greatly acknowledged.Liu, L.; Lopez-Haro, M.; Lopes, CW.; Rojas-Buzo, S.; Concepción Heydorn, P.; Manzorro, R.; Simonelli, L.... (2020). Structural modulation and direct measurement of subnanometric bimetallic PtSn clusters confined in zeolites. Nature Catalysis. 3(8):628-638. https://doi.org/10.1038/s41929-020-0472-7S62863838Liu, L. & Corma, A. Metal catalysts for heterogeneous catalysis: from single atoms to nanoclusters and nanoparticles. Chem. Rev. 118, 4981–5079 (2018).An, K. & Somorjai, G. A. Nanocatalysis I: synthesis of metal and bimetallic nanoparticles and porous oxides and their catalytic reaction studies. Catal. 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Plasma engineering of microstructured piezo – Triboelectric hybrid nanogenerators for wide bandwidth vibration energy harvesting

We introduce herein the advanced application of low-pressure plasma procedures for the development of piezo and triboelectric mode I hybrid nanogenerators. Thus, plasma assisted deposition and functionalization methods are presented as key enabling technologies for the nanoscale design of ZnO polycrystalline shells, the formation of conducting metallic cores in core@shell nanowires, and for the solventless surface modification of polymeric coatings and matrixes. We show how the perfluorinated chains grafting of polydimethylsiloxane (PDMS) provides a reliable approach to increase the hydrophobicity and surface charges at the same time that keeping the PDMS mechanical properties. In this way, we produce efficient Ag/ZnO convoluted piezoelectric nanogenerators supported on flexible substrates and embedded in PDMS compatible with a contact–separation triboelectric architecture. Factors like crystalline texture, ZnO thickness, nanowires aspect ratio, and surface chemical modification of the PDMS are explored to optimize the power output of the nanogenerators aimed for harvesting from low-frequency vibrations. Just by manual triggering, the hybrid device can charge a capacitor to switch on an array of color LEDs. Outstandingly, this simple three-layer architecture allows for harvesting vibration energy in a wide bandwidth, thus, we show the performance characteristics for frequencies between 1 Hz and 50 Hz and demonstrate the successful activation of the system up to ca. 800 Hz.EMERGIA Junta de Andalucía programUniversity of Seville the VI PPIT-USICMS and the CITIUS from the University of Sevill

Low temperature plasma processing of platinum porphyrins for the development of metal nanostructured layers

This article establishes the bases for a vacuum and plasma supported methodology for the fabrication at mild temperatures of nanostructured platinum in the form of porous layers and nanocolumns using platinum octaethylporphyrin as precursor. In addition, the application of these materials as tunable optical filters and nano-counterelectrodes is proved. On one hand, the transparency in the ultraviolet-visible-near infrared range can be adjusted precisely between 70% and 1% by tuning the deposition and processing conditions, obtaining a high spectral planarity. Deviations of the spectra from an ideal flat filter are below 4%, paving the way to the fabrication of neutral density filters. The transparency limit values yield a sheet resistivity of ¿1350 and 120 ¿ ¿-1, respectively. On the other hand, the catalytic properties of the nanostructures are further demonstrated by their implementation as counterelectrodes of excitonic solar cells surpassing the performance of commercial platinum as counterelectrode in a 20% of the overall cell efficiency due to simultaneous enhancement of short-circuit photocurrent and open-circuit photovoltage. One of the most interesting features of the developed methodology is its straightforward application to other metal porphyrins and phthalocyanines readily sublimable under mild vacuum and temperature conditions.Junta de AndaluciaTEP8067 FQM-6900 FQM 1851 P12-FQM-2265España MinecoMAT2013-40852-R MAT2013-42900-P MAT2013-47192-C3-3-RMAT2016-79866-RMINECO-CSIC 201560E055

A Full Vacuum Approach for the Fabrication of Hybrid White-Light-Emitting Thin Films and Wide-Range In Situ Tunable Luminescent Microcavities

This study shows the fabrication by a dry approach at mild temperature (<150 °C) of a photoluminescence white light emitting hybrid layer. The white light emitter is obtained by evaporation of two photoluminescent small molecules, a blue (1,3,5-triphenyl-2-pyrazoline (TPP)) and an orange (Rubrene) dye within the porous of an SiO host film fabricated by glancing angle deposition. Fluorescence (Föster) resonant energy transfer between the two organic dyes allows the emission of the combined system upon excitation of the TPP molecule at wavelength of 365 nm. The distribution of the organic molecule within the host layer is analyzed as a function of the substrate temperature and vacuum conditions and the required conditions for the white emission determined by finely controlling the TPP:Rubrene ratio. The full vacuum processing of the hybrid layers provides a straightforward route for the incorporation of the white light emitters as optical defect within 1D Bragg microcavities. As a consequence, directional emission of the system is achieved which allows the development of wide-range in situ tunable photoluminescent devices.Junta de Andalucía TEP8067, FQM-6900, P12-FQM-2265Ministerio de Economía y Competitividad MAT2013-40852-R, MAT2013-42900-

Supported Ce/Zr pyrochlore monolayers as a route to single cerium atom catalysts with low temperature reducibility

Summary: The combination of structural characterization at atomic resolution, chemical data, and theoretical insights has revealed the unique nanostructures which develop in ceria supported on yttria-stabilized zirconia (YSZ) after being submitted to high-temperature reducing treatments. The results show that just a small ceria loading is needed for creating a supported Zr-rich pyrochlore (111) nanostructure, resembling the structure of single cerium atom catalysts. The specific atomic arrangement of this nanostructure allows to explain the improvement of the reducibility at low temperature. The reduction mechanism can be extrapolated to ceria-zirconia mixed oxides with pyrochlore-like cationic ordering, exposing Zr-rich (111) surfaces. The results gathered here provide key information to understand the redox behavior of these types of systems, which may contribute to improving the design of new ceria-zirconia based materials, with lower content of the lanthanide element, nearly 100% cerium atom utilization, and applications in environmental catalysis

Improving the reducibility of CeO2/TiO2 by high-temperature redox treatment: the key role of atomically thin CeO2 surface layers

CeO2/TiO2 catalysts treated in reaction environment at high temperatures evolve into complex and diverse systems, where several mixed oxides are formed. To analyze the redox behavior of this system, multiple oxidations and reducing thermal treatments have been applied. Results from the temperature-programmed reduction studies revealed a clear shift at lower temperatures on the reduction peak when the sample was previously reduced at high temperatures and oxidized under mild conditions. Meanwhile, the reduction peak was moved to high temperatures when the sample was previously reduced and oxidized at severe temperatures. The study, which was aimed at correlating this behavior with its chemical structure, was conducted using advanced electron microscopy, including high-resolution TEM and STEM imaging and spectroscopic techniques such as X-EDS and EELS. The data presented here comparing structures at the atomic level and chemical properties have uniquely unveiled that besides the cerium-titanium mixed oxides, a very thin layer up to a single monolayer was deposited along the TiO2 surface, which indeed was responsible for the improvement of the reducing temperature

Spin to charge conversion in chemically deposited epitaxial La0.9MnO3 thin films capped with Pt

Spin to charge conversion process in a broad range of temperatures is studied in La0.92MnO3/Pt bilayers prepared by polymer-assisted deposition (PAD). It is shown that an excellent LMO/Pt interface can be obtained in spite of using ex situ deposition of the Pt layer. The values obtained for the effective spin-mixing conductance, g↑↓eff = 0.76 × 1015 cm−2, suggest that significant spin transport across the LMO/Pt interface could be achieved. Spin pumping experiments generate a transversal voltage signal VISHE, due to spin to charge conversion via inverse spin Hall effect, that has been detected down to about 100 K with values of the spin-Hall angle, θSH, of about 2.5%, slightly decreasing on reducing temperature in the analyzed temperature range. These results indicate that LMO is a promising perovskite building block for all-oxide multifunctional high-frequency spintronics devices and that PAD technique provides oxide epitaxial thin films of good quality adequate for spintronic applications.We acknowledge financial support from the Spanish Ministry of Science, Innovation and Universities through Severo Ochoa (CEX2019-000917-S), and SPINCURIOX (RTI2018-099960-BI00) and AMONANO (PID2020-112914RB-I00) projects co-financed by the European Regional Development Funds. AMONANO also received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement no. 823717-ESTEEM3. Hailin Wang acknowledges financial support from the China Scholarship Council (CSC).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

CeO2-modified Au/TiO2catalysts with outstanding stability underharsh CO oxidation conditions

Depto. de Química InorgánicaFac. de Ciencias QuímicasTRUEpu