Effect of the Sintering Temperature of Gd<sub>2</sub>O<sub>3</sub>:Er,Yb as a Raw Material of Upconversion Nanoparticles

Aiming to expand the application range of photodynamic therapy, we investigated Gd2O3:Er,Yb as a sintered raw material for the synthesis of upconversion nanoparticles and the effect of the sintering temperature, which is important because of its large effect on luminescence. Increasing the sintering temperature of the raw material resulted in a higher emission intensity because of higher crystallinity. Moreover, although the primary particle size of the raw material increased with temperature, the crystal structure remained unaltered. Because raw materials hardened at high temperatures, higher laser fluence was used to fabricate nanoparticles to reduce size via laser ablation in liquids.