Wet chemical synthesis and photoluminescence properties of YVO4:Bi3+,Eu3+ nanophosphors

Abstract

YVO4:Bi3+,Eu3+ nanoparticles were prepared by the wet chemical synthesis in various concentrations of sodium citrate, 15 ≤ xcit ≤ 90, where xcit is the nominal molar percentage of citrate relative to the sum of metallic ions, Y3+, Bi3+, and Eu3+. Mean primary particle size and mean hydrodynamic size in the aqueous colloidal solution have minimum values, 21 and 36 nm, respectively, for the sample prepared at xcit = 50 mol%. The transparency of the aqueous colloidal solution in the visible region increases with decreasing the mean hydrodynamic size, and hence the sample prepared at xcit = 50 mol% shows the highest transparency. YVO4:Bi3+,Eu3+ nanophosphor synthesized by the citrate route shows the photobleaching behavior, i.e., the decrease in photoluminescence intensity under the continuous irradiation of excitation light. This photobleaching property is remarkably suppressed by the washing post-treatment combined with centrifugation and the hydrothermal post-treatment. A relation between the fraction of photobleach and the amount of citrate ions coordinating to metallic ions at the surface of nanoparticles verifies that the photobleaching behavior of YVO4:Bi3+,Eu3+ nanophosphor originates from the redox reaction between the citrate ions and V5+ in YVO4 host crystal.