Silica-coating of fluorescent polystyrene microspheres by a modified Stöber method and their stability against photobleaching

Abstract

AbstractSubmicron-sized polystyrene spheres incorporating fluorescence dyes (fluorescent microspheres) were coated with silica by means of a seeded polymerization technique based on the Stöber method. Silica-coating of the fluorescent microspheres with a size of 100 nm was performed in the presence of 0 - 10 g/l polyvinylpyrrolidone (PVP), 1 - 13 mol/l water, 0 - 0.8 mol/l aq. ammonia and 0.00038 - 0.2 mol/l tetraethoxyorthosilicate (TEOS). The addition of PVP was found to suppress the generation of free silica particles and produced no shell-free fluorescent microspheres improving the uniformity of shell thickness of silicacoated fluorescent microspheres. Silica shell thickness increased from 11 to 63 nm with increasing TEOS concentration at 10 g/l PVP, 0.4 mol/l aq. ammonia and 11 mol/l water. Silica-coated fluorescent microspheres showed more stable fluorescence to laser-irradiation than uncoated fluorescent microspheres.