Elucidating the Effects of a Rare-Earth Oxide Shell on the Luminescence Dynamics of Er3+:Y2O3Nanoparticles

Abstract

Rare-earth (RE) (Er3+ and Yb3+, Er3+)-doped yttrium oxide (Y2O3) core–shell particles were synthesized in this work using a two-step process where the cores were formed by molten salt synthesis while the shell was deposited by a sol–gel process. The cores were 100–150 nm, and a shell layer, up to 12 nm thick, was controllable based on the mass ratio between the RECl3 salts and the Er3+:Y2O3 (1 mol %) particles. A passive Y2O3 shell layer, at an optimal thickness around 8 nm, passivated the surface quenching sites and resulted in a 53% increase in photoluminescence lifetimes and visible separation in Stark splitting. Optically active shell layers, such as Yb2O3 and Yb3+:Y2O3, not only passivated the quenching sites but also facilitated energy transfer between the spatially controlled RE ions. Furthermore, the effect of surface passivation on the upconversion luminescence was determined through the purposed dynamic processes to corroborate the effect of the hydroxyl groups on energy dissipation. The additio...