Preparation and luminescence properties of monodisperse silica/aminosilane-coated Y2O3:Yb,Ho upconversion nanoparticles

Monodisperse silica/aminosilane-coated Y2O3:Yb,Ho nanoparticles are prepared via homogenous precipitation combined with a polyvinylpyrrolidone-assisted ammoniation method. The factors that contribute to the success of the coating are examined, and the procedure is optimized. Compared with uncoated nanoparticles, coated nanoparticles exhibit an increased ratio of green to red emission intensity, which can mainly be attributed to the decreased number of surface defects induced by the surface coating.