Enhanced photoluminescence from Gd2O3:Eu3+ nanocores with a Y2O3 thin shell

Abstract

Nanoparticles of Gd₂O₃:Eu³⁺ ∼20 nm in diameter were synthesized at ∼180 °C using a facile high boiling-point alcohol (polyol) method. The Gd₂O₃ nanoparticles, doped with 5 mol% Eu, were crystalline cubic phase and exhibited intense ⁵D₀–⁷F₂ photoluminescence (PL) from Eu³⁺ after calcination at 600 °C for 2 h in air. Photoluminescence excitation (PLE) data showed that while a small fraction of the emission resulted from direct excitation of Eu³⁺, most of the excitation resulted from adsorption in the oxygen to europium charge-transfer band between 225 and 275 nm. Transmission electron microscopy (TEM) images showed that the Gd₂O₃:Eu³⁺ cores were slightly agglomerated, but the thin Y₂O₃ shell could not be detected by TEM. X-Ray photoelectron spectroscopy (XPS) was used to detect the thin Y₂O₃ shell around the Gd₂O₃:Eu³⁺ core. Drop-cast thin films of the Gd₂O₃:Eu³⁺/Y₂O₃ core/shell nanoparticles exhibited PL intensities up to 40% larger than from bare core Gd₂O₃:Eu³⁺ nanoparticles. Increased PL was attributed to reduced non-radiative recombination based on longer luminescence decay times.