Microwave hydrothermal synthesis and upconversion properties of Yb 3+ /Er 3+ doped YVO 4 nanoparticles.

Yb3+ and Er3+ doped YVO4 (Yb3+ /Er3+ :YVO4 ) nanoparticles with highly efficient near-infrared to visible upconversion properties have been synthesized by microwave hydrothermal process. Uniform-sized Yb3+ /Er3+ :YVO4 nanoparticles were synthesized within 1 h at 140 °C which is relatively faster than the conventional hydrothermal process. Under 980 nm laser excitation, strong green and less strong red emissions are observed which are attributed to 2 H11/2 , 4 S3/2 to 4 I15/2 and 4 F9/2 to 4 I15/2 transitions of Er3+ respectively. The emission intensity is found to depend strongly on the concentration of Yb3+ . The quadratic dependence of upconversion intensity on the excitation power indicates that the upconversion process is governed by two-photon absorption process.