Understanding the infrared to visible upconversion luminescence properties of Er3+/Yb3+ co-doped BaMoO4 nanocrystals

In this paper we report the infrared to visible upconversion luminescence properties of Er3+/Yb3+ co-doped BaMoO4 nanocrystals synthesized via microwave assisted sol-gel processing route. Structural, morphological and upconversion luminescence properties were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and Upconversion Photoluminescence spectra analysis. Results revealed that the oval shaped BaMoO4 nanocrystals ranging in size from 40 to 60 nm having tetragonal scheelite crystal structure were obtained by sol-gel route. The infrared to visible upconversion luminescence has been investigated in Er3+/Yb3+ co-doped in BaMoO4 with different Yb3+ concentrations. Intense green upconversion emissions around 528. 550 nm, and red emission at 657 nm corresponding to the H-2(11/2), S-4(3/2), and F-4(9/2) transitions, respectively to the I-4(15/2) ground state were observed when excited by CW laser radiation at 980 nm. The green emissions were greatly enhanced after the addition of sensitizer (Yb3+ ions). The effect of Yb3+ on the upconversion luminescence intensity was analyzed and explained in terms of the energy transfer process based. The reported work establishes the understanding of molybdates as an alternative host material for upconversion luminescence. (C) 2014 Elsevier Inc. All rights reserved.