Navegando por Autor "Silva, J.M.P."
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Artigo Stabilization of the γ-Ag2WO4 metastable pure phase by coprecipitation method using polyvinylpyrrolidone as surfactant: photocatalytic property(Elsevier, 2020-07) Andrade Neto, Nivaldo Freire de; Silva, J.M.P.; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela daIn this work, the effect of polyvinylpyrrolidone (PVP) concentration as a surfactant was studied in the estabilization of the metastable phase γ-Ag2WO4 by the coprecipitation method at room temperature. The phases obtained were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and spectroscopy in the ultraviolet–visible region (UV–Vis). The pho-tocatalytic activity was estimated by varying the concentration of methylene blue dye. The iffractograms in-dicate that 0.3 g of PVP is ideal for obtaining the single phase of γ-Ag2WO4, as larger or maller amounts favor the appearance of β-Ag2WO4 as a secondary phase while the absence of PVP formed he α-Ag2WO4 phase. UV–Vis spectroscopy showed that both phases have absorption in the ultraviolet region, here the γ-Ag2WO4 phase has a higher absorption at shorter wavelengths. The micrographs indicate that the -g2WO4 morphology is formed by rods, while the γ-Ag2WO4 is formed by octahedrons, both in micrometer cale and with well-defined morphology. The photocatalytic tests indicate that the γ-Ag2WO4 phase has better photocatalytic activity compared to the β-Ag2WO4 phase. The scavenger's methodology indicated that h+ charges are the main mechanism in the photocatalysis of methylene blue dye