Treatment of TiO2 for the suppression of photo-catalytic property and dispersion stability

To be used as absorber of UV-ray in cosmetic products, UV-ray absorption ability of TiO2 has to be increased and particle size of TiO2 has to be reduced up to nanosize. TiO2 was coated with inorganic layer of silica to suppress photo-catalytic activity and to increase dispersibility. Silica-coated TiO2 nanoparticle was prepared with commercial TiO2 (Degussa P-25) and TEOS. TiO2 Was treated with 0.1 M HCl to prevent aggregation. The pH of TEOS was adjusted in the range of 7-8 by adding 0.1 M NH4OH. Silica-coated TiO2 nanoparticle included the structures of core-shell by TEM images. The decrease of photocatalytic activity and UV shielding effect of silica-coated TiO2 nanoparticles was confirmed with UV-vis spectra. Improved dispersion of silica-coated TiO2 nanoparticles as compared with pure TiO2 was verified with increased Zeta potential value. The dispersion of TiO2 nanoparticle was also studied on the effect of oleate coating on TiO2 nanoparticle surface.