Abstract
▶ Titania nanoparticles were coated with silica shell via solvothermal process. ▶ Optimization of solvothermal parameters resulted in dense silica coating of TiO
2. ▶ Porosity and FTIR measurements suggested the dense character of silica shell. ▶ Silica shell effectively suppressed the photocatalytic activity of TiO
2. ▶ UV-shielding ability of the coated titania was not reduced by silica coating.
Due to its excellent UV-rays shielding properties, titanium dioxide can be used in many sunscreen products. However, concerns have been raised about the possible photocatalytic decomposition of cosmetic formulation by titanium dioxide. Therefore, titania nanoparticles were encapsulated in silica shell by using solvothermal process. Both temperature and time parameters of the solvothermal process were optimized to produce silica shell with highest density (loss of micropores) and maximum shell thickness. The coated particles were characterized by X-ray diffraction (XRD), TEM, FTIR, XPS, zeta-potential, and porosity measurements. The photocatalytic activity of the coated samples was suppressed effectively by conducting solvothermal silica coating at 200
°C for 15
h where TEM observations revealed the gradual growth of silica shell around TiO
2 nanoparticles. On the other hand, UV-shielding properties were slightly reduced after silica coating which can be attributed to the loss of titania content.