Synthesis and upconversion properties of monoclinic Gd2O3:Er3+ nanocrystals

Monoclinic phase Gd2O3:Er3+ nanophosphors were synthesized by the glycine-nitrate process (GNP). Green, red and blue/ultraviolet (UV) radiations were observed by 980 nm diode laser excitation. Obvious enhancement of the red and blue/UV emissions from the 4F9/2, 2H9/2 and 4G11/2 levels were observed with increasing Er3+ ions doping concentration. Power dependence study revealed that two and three photons processes are involved in the upconversion process. Emissions excited by an Ar+ laser verified the analysis of the upconversion mechanism and indicated that the phonon assisted energy transfer process 4I11/2 + 4I11/2— 4F9/2 + 4I13/2 becomes prominent and greatly enhances both the red and blue/UV upconversions with increasing Er3+ ion doping.