Abstract
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. Dense 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. Depression of high photocatalytic activity of titania necessitates that silica shell has to be thick and with minimum microporosity. Coating parameters were optimized to attain higher precipitated silica wt%, thicker shell and lower microporsity which in turn resulted in great depression of photocatalytic activity. Silica coated titania nanoparticles were characterized by TEM, XPS, FT-IR, EDX and microporsity. The photocatalytic activity was evaluated for the coated powder to investigate the efficiency of silica coating as well.
