Fabrication of Monodispersed, Multilayered Silica-Y:Eu-Silica Core-Shell Particles and Their Photonic Crystals

Abstract

Methods for preparing monodispersed, multilayered silica-Y:Eu-silica core-shell particles and for fabricating their colloidal photonic crystals are proposed. Silica-Y:Eu core-shell particles with a size of 360 nm were synthesized with a homogeneous precipitation method at 80°C in a 50/50 (v/v) water/propanol solution at 0.0009 mol/dm3 Y(NO3)3, 0.0001 mol/dm3 Eu(NO3)3, 0.5 mol/dm3 urea, 1 g/dm3 polyvinylpyrrolidone (PVP) and 0.01 vol% suspension of silica particles with an average size of 330 nm. Succeeding silica-coating of the silica-Y:Eu core-shell particles was performed in ethanol at 10 mmol/dm3 tetraethylorthosilicate, 11 mol/dm3 H2O, 0.5 mol/dm3 ammonia, 5 mmol/dm3 acetic acid, 1 g/dm3 PVP and 0.001 vol% suspension of silica:Eu core-shell particles. Consequently, multilayered silica-Y:Eu-silica core-shell particles with an average size of 460 nm and a coefficient of variation as low as 3.0% could be obtained. Colloidal crystals composed of these particles exhibited both reflection based on Bragg diffraction and luminescence of Y:Eu.