Microwave-assisted hydrothermal synthesis of Ag2(W1 -xMox)O4 heterostructures: Nucleation of Ag, morphology, and photoluminescence properties

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Volume 153, 15 January 2016, Pages 428-435, ISSN 1386-1425

Figure: FE-SEM images of Ag2W0.50Mo0.50O4 crystals after electron beam exposure for different times (a) 0 min, (b) 1 min, (c) 2 min, (d) 3 min, (e) 4 min and (f) 5 min.

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Writers: M.D.P. Silva, R.F. Gonçalves, I.C. Nogueira, V.M. Longo, L. Mondoni, M.G. Moron, Y.V. Santana, E. Longo

Keywords: Ag2WO4; Ag2MoO4; Photoluminescence; Morphology; Raman spectroscopy

Abstract: Ag2W1 -xMoxO4 (x = 0.0 and 0.50) powders were synthesized by the co-precipitation (drop-by-drop) method and processed using a microwave-assisted hydrothermal method. We report the real-time in situ formation and growth of Ag filaments on the Ag2W1 -xMoxO4 crystals using an accelerated electron beam under high vacuum. Various techniques were used to evaluate the influence of the network-former substitution on the structural and optical properties, including photoluminescence (PL) emission, of these materials. X-ray diffraction results confirmed the phases obtained by the synthesis methods. Raman spectroscopy revealed significant changes in local order–disorder as a function of the network-former substitution. Field-emission scanning electron microscopy was used to determine the shape as well as dimensions of the Ag2W1 -xMoxO4 heterostructures. The PL spectra showed that the PL-emission intensities of Ag2W1 -xMoxO4 were greater than those of pure Ag2WO4, probably because of the increase of intermediary energy levels within the band gap of the Ag2W1 -xMoxO4 heterostructures, as evidenced by the decrease in the band-gap values measured by ultraviolet–visible spectroscopy.

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