Red and green upconversion luminescence of Gd2O3:Er3+, Yb3+ nanoparticles

Gd2O3:Er3+, Yb3+ nanoparticles have been synthesized by a homogeneous precipitation method with EDTA 2Na of two different concentrations. Upconversion luminescence spectra of the samples have been studied under 980 nm laser excitation. The results of XRD show that obtained Gd2O3:Er3+, Yb3+ nanoparticles are of a cubic structure. The average crystallite sizes could be calculated as 22 and 29 nm, respectively. The strong green and red upconversion emission were observed, and attributed to the H-2(11/2), S-4(3/2) -> I-4(15/2) and F-4(19/2) -> I-4(15/2) transitions of Er3+ ion, respectively. The ratio of the intensity of green emission to that of red emission has drastic changed with an EDTA 2Na concentration changed. The intention of green and red emission controlled in Gd2O3:Er3+, Yb3+ nanocrystals is achieved by a varying concentration of EDTA 2Na, and the possible mechanisms are discussed. (C) 2007 Elsevier B.V All rights reserved.