Dense silica coating of titania nanoparticles by seeded polymerization technique

Titania is of potential interest as an ultraviolet (UV) radiation blocking material in personal care products because of its excellent UV light absorption property. Its high photocatalytic activity, however, facilitates the generation of reactive oxygen species, which can oxidize and degrade other ingredients during its formulation, raising safety concerns. Coating of titania nanoparticles; with a silica layer could help in depression of their photocatalytic activity by disturbing the formation of radicals produced by the reaction of oxygen and/or water with the electron-hole pair. Titania nanoparticles were coated with amorphous silica using a seeded polymerization technique. The silica shell was confirmed by TEM, electron probe micro-analysis (EPMA), and FT-IR. The photocatalytic activity was evaluated for the coated powder to investigate the efficiency of silica coating as well. (c) 2005 Elsevier B.V. All rights reserved.