RESUMO
Understanding how a photocatalyst modulates its oxidation state, size, and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physicochemical techniques and probes employed to study them. A synchrotron micro-beam X-ray absorption spectroscopy study together with the computational simulation and analysis (at the X-ray cell) of the light-matter interaction occurring in powdered TiO2 -based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non-noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu-Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials.
RESUMO
Cu/TiO2/SrTiO3 hybrid structures have been synthesized by the simple impregnation method from Cu/TiO2 and SrTiO3 systems. The structural and surface characterization stated that Cu/TiO2/SrTiO3 composites form an effective covering of SrTiO3 by Cu/TiO2. The heterostructured catalysts lead to an outstanding improved photoactivity for hydrogen production from methanol photoreforming that would be related with the efficient separation of charge pairs favored by the Cu/TiO2/SrTiO3 heterojunction. The best photoproduction is attained for the 30 wt % SrTiO3 heterojunction showing 81.7 mmol/g H2 after 6 h (leading to an apparent quantum yield of ca 1%), 1.7 times higher than that of bare Cu/TiO2.
RESUMO
A systematic review was employed utilizing Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, to analyze all primary clinical data on the efficacy of spinal cord stimulation (SCS) in the treatment of multiple sclerosis (MS) induced spasticity. Databases include: Embase, PubMed, Scopus, Cochrane, and Web of Science. The review included case series, case studies, and clinical trials. Outcomes of interest were spasticity reduction. Grading of Recommendations Assessment, Development and Evaluation criteria was utilized to grade the certainty of evidence. Five hundred thirty-two articles were retrieved following database systematic review. One hundred eighty-eight articles were removed as duplicates utilizing the "Detect Duplicates" function on Rayyan.ai. A further 344 articles were excluded following abstract and title appraisal. As a result, 16 articles were subjected to full text appraisal. The dates of publication ranged from 1973 to 2019. Although a unique modality, there is not enough evidence to support the employment of SCS over current medical standard of care. Further high-quality randomized control trials are required to elucidate SCS's role in MS induced spasticity algorithm.
RESUMO
We report on a novel synthesis method, which produces NaY(MoO4)2 nanoparticles having an almost spherical shape and hydrophilic character. The procedure is also suitable for the preparation of NaY(MoO4)2-based nanophosphors by doping this host with lanthanide cations (Eu3+, Tb3+ and Dy3+), which, under UV illumination, exhibit intense luminescence whose color is determined by the selected doping cation (red for Eu3+, green for Tb3+ and yellow for Dy3+). The effects of the cations doping level on the luminescent properties are analyzed in terms of emission intensities and luminescent lifetime, to find the optimum phosphors. Finally, the performance of these nanophosphors and that of the undoped system for the photocatalytic degradation of rhodamine B, used as a model compound, is also analyzed.
RESUMO
Er-doped BiVO4 are synthesized by means of a surfactant free microwave assisted hydrothermal method having good photoactivities under sun-like excitation for the degradation of methylene blue. From the structural and morphological characterization, it has been stated that the presence of Er(3+) induces a slight stabilization of the tetragonal phase, probably due to its incorporation in the BiVO4 lattice. The best photocatalytic performances were attained for the samples with Er(3+) content higher than 3 at%. The occurrence of the Er(3+) doped tetragonal BiVO4 clearly induces higher photocatalytic activities. The existence of a luminescence process has been related with the enhanced photoactivity observed.
RESUMO
Single-phase anatase-TiO2 nanomaterials with a size of ca. 10 nm and variable quantities of anion impurities were prepared using a novel pathway based on the use of amorphous ammonium Ti-oxychloride precursors synthesized using Ti/Cl initial ratios between 1 and 6. The precursor nature and evolution under thermal treatment were studied using chemical analysis, XRD, XPS, DRIFTS, and mass spectrometry. The nature and concentration of anatase-TiO2 materials anion impurities were analyzed by XPS and DRIFTS. It is shown that negatively charged impurities located in substitutional positions of the anatase network are maximized for a sample synthesized using a Ti/Cl 1:1 atomic ratio and are responsible for the elimination of liquid-phase (phenol) and gas-phase (isopropanol or methylcyclohexane) pollutants under sunlight excitation. A link is established among the initial chemical characterization of the precursors, the final morphological, structural, and chemical composition of the oxide materials, and their photochemical properties.