Navegando por Autor "Nunes, T. B. O."
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Artigo Effect of temperature on the photocatalytic properties of TiO2 -CeO2 multilayer thin films obtained by spin coating method(ABCERAM, 2020) Nunes, T. B. O.; Andrade Neto, Nivaldo Freire de; Garcia, Laurênia Martins Pereira; Nascimento, Rubens Maribondo do; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daTiO2-CeO2 multilayer thin films were deposited by the spin coating method and calcined at 500 and 700 °C. Thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and diffuse reflectance spectroscopy. Photocatalytic properties were estimated by varying the concentration of the methylene blue dye (MB) when illuminated by UV radiation. The XRD patterns showed that the temperatures of 500 and 700 °C were effective to obtain TiO2 and CeO2 phases. The difference in the homogeneity of TiO2 and CeO2 films was evident in the AFM images, where the films showed an average roughness of 2.0 and 5.3 nm, respectively. The CeO2 -TiO2 thin film obtained at 700 °C showed the best photocatalytic activity, reducing the concentration of MB by approximately 80%, while the CeO2 and TiO2 films obtained at 700°C reduced only 20% and 29%, respectively. The reuse test showed that the thin films maintained their photocatalytic activity after 4 cycles, and there was no need for thermal treatment, indicating that it is an immobilized photocatalyst with high efficiency in the degradation of organic dyesArtigo 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