Green synthesis of upconversion nanocrystals by adjusting local precursor supersaturation under aqueous conditions

Abstract

We describe a green synthesis of upconversion nanocrystals (UCNs) by adjusting local precursor supersaturation under aqueous conditions at low temperature with size and phase control as well as high production yield. The synthesis allows the separation of nucleation and growth, leading to the formation of small UCNs with a uniform size. Ultra-small α-phase UCNs (∼6.3 nm) and bright β-phase UCNs (∼25.5 nm) have been synthesized.