Surface Treatment of Broad-Spectrum Ultraviolet Light Shielding Titania/Zinc Oxide Composites and Their Applications in Sunscreens

Nano-titanium oxide (TiO2) and zinc oxide (ZnO) are widely used in sunscreen products, but many shortcomings for these both oxides still exist. In this paper, the hydrolysis of tetraethyl orthosilicate (TEOS) in ethanol solution was used to deposit inorganic silica nano-coating on the surface of TiO2/ZnO composite, followed by grafting by organosilane. The as-prepared products were characterized by XRD, FTIR, TG and TEM. In addition, Zeta potential, color difference test, dissolution experiments of zinc ions and water contact angle tests were used to characterize the effect of inorganic silica coating and organosilane grafting. Subsequently, the modified TiO2/ZnO composites were applied into the sunscreen formulation and the properties of the as-prepared emulsions were evaluated by the distribution analysis of the particle size, acceleration test and ultraviolet transmittance analyzer. The results showed that the sunscreen emulsion prepared by the TiO2/ZnO composite has better sun protection performance and stability than the emulsion prepared by the mixture of TiO2 and ZnO.