Synthesis, characterization, and enhanced luminescence of CaWO4:Eu3+/SBA-15 composites

Abstract

Considering the combination of lanthanidedoped CaWO 4 nanophosphor and mesoporous matrix may contribute to superior luminescent properties, CaWO 4 : Eu 3? /SBA-15 composites were successfully synthesized in a mild condition. The physicochemical properties of the resultant composites were carefully characterized by X-ray diffraction, high-resolution transmission electron microscopy, inductive coupled plasma optical emission spectroscopy (ICP), N 2 adsorption-desorption, Fourier transform infrared spectroscopy, and luminescence spectra. It's found that the incorporation of CaWO 4 :Eu 3? showed no obvious impact on the ordered mesostructure of the host matrix SBA-15, which, however, led to a decrease of BET surface area from 836 to 187 m 2 g -1 for pure SBA-15 and CES (0.5), respectively. ICP results indicated that the real loaded amount of CaWO 4 :Eu 3? in SBA-15 host was lower than the initial molar ratios (x) of CaWO 4 :Eu 3? to SBA-15 for all samples. The maximum loaded level of CaWO 4 :Eu 3? in SBA-15 is about 27.3 %. Moreover, the real Eu 3? dopant concentration increased with the initial molar ratios (x), which showed a maximum of about 6.51 % at x = 0.25. The resultant CaWO 4 :Eu 3? /SBA-15 composites exhibited enhanced-luminescent properties than that of pure CaWO 4 :Eu 3? nanoparticles, which can be mainly attributed to the variation of Eu 3? dopant concentration and the hostprotect effect through interaction between guest molecules and host matrix. The available large surface area, pore volume, and superior luminescent properties would facilitate future applications for the composites.

Síntese pelo método da coprecipitação e caracterização estrutural do tungstato de cálcio com estrutura tipo scheelita

“…O processo de precipitação deverá ser quantitativo e simultâneo, sem que ocorra a separação preferencial de alguns dos constituintes nos precipitados formados. Em alguns casos, é necessário um controle rígido de parâmetros como o pH da solução, viscosidade, temperatura, concentração dos reagentes e controle na diferenças de solubilidade entre as várias fases precipitantes que afetam fortemente a cinética de precipitação, para a obtenção de pós com as características adequadas [13,14].…”