Navegando por Autor "Andrade Neto, Nivaldo Ferreira da"
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Artigo Connecting theory with experiment to understand the photocatalytic activity of CuO–ZnO heterostructure(Elsevier, 2020-05) Oliveira, Marisa Carvalho de; Fonseca, V. S.; Andrade Neto, Nivaldo Ferreira da; Ribeiro, Renan Augusto Pontes; Silva, Elson Longo da; Lazaro, Sérgio Ricardo de; Motta, Fabiana Villela da; Delmonte, Maurício Roberto BomioSemiconductor based photocatalysis attracts wide attention because of its ability to directly utilize solar energy to degrade pollutants and convert energy, with heterojunction photocatalysts being good candidates for superior activity due to the spatial separation of photogenerated electron–hole pairs. Herein, CuO/ZnO heterostructures were successfully synthesized by a microwave-assisted hydrothermal method, with the structure, electronic and photocatalytic properties analyzed by means of experimental and theoretical methods. The X-ray diffraction patterns revealed that a CuO/ZnO heterostructure was formed, while FE-SEM analysis indicates the role of different morphologies for CuO, ZnO and CuO/ZnO heterostructures. The solar-driven photocatalytic mea-surements combined with DFT calculations indicate that CuO, as a p-type and narrow band-gap sensitizer, can make the n-type ZnO respond to visible light and promote the separation of photogenerated charge carriers by building a p-n heterogeneous structure. As a result, the CuO/ZnO heterostructure shows good promise for solar-driven photodegradationArtigo Influence of microwave-assisted hydrothermal treatment time on the crystallinity, morphology and optical properties of ZnWO4 nanoparticles: Photocatalytic activity(Elsevier, 2020-02-01) Andrade Neto, Nivaldo Ferreira da; Nunes, T. B. O.; Li, Máximo Siu; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daIn this work, zinc tungstate (ZnWO4) nanoparticles were obtained by microwave-assisted hydrothermal method at 140 °C and 2 atm. The hydrothermal treatment time was varied at 0, 5, 10, 30, 60 and 120 min. The nano- particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scan- ning electron microscopy (SEM), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), X-ray fluorescence (FRX), nitrogen adsorption by Brunauer-Emmett-Teller method (BET), UV–Visible spectroscopy (UV–Vis) and Photoluminescence (PL) properties. The adsorptive and photocatalytic properties were estimated against methylene blue (MB - cationic) and methyl orange (MO - anionic) dyes. The diffractograms show that the larger hydrothermal treatment time, anhigher the powders crystallinity. The BET and SEM analysis indicate that the increase in hydrothermal time does not interfere significantly in nanoparticles size but reduces their porosity. The change in the surface area is consistent with the adsorption tests, where the increase of the hydrothermal treatment time reduces the adsorption against the MB and MO dyes. However, increasing the hydrothermal treatment time provides an increase in photocatalytic activity