Synthesis of TiO₂ Nanoparticles Coated with SiO₂ for Suppression of Photocatalytic Activity and Increased Dispersion Stability

다국어 초록 (Multilingual Abstract)

For its use as an absorber of UV light in cosmetic products, TiO₂ was coated a with a SiO₂ layer to suppress its photocatalytic activity and to increase its dispersion ability. Silica-coated TiO₂ nanoparticles were prepared by a sol-gel process. High-resolution transmission electron microscopy (HRTEM) and X-ray photo-electron spectroscopy (XPS) analyses showed that hydrous silica was coated evenly on the surface of the TiO₂ particles. The effect of heat-treatment on the products, i.e., increasing annealing time and temperature, was followed by X-ray powder diffraction (XRD) spectroscopy. To study the suppression of the photocatalytic effect, an organic compound was added to the silica-coated TiO₂ sol and the solution was irradiated with UV light. The decrease in the photocatalytic activity and the UV shielding effect of the silica-coated TiO₂ nanoparticles were confirmed by recording UV-vis spectra, which showed more than an 80% decrease in the photocatalytic effect. Improved dispersion of the silica-coated TiO₂ nanoparticles, as compared with that of pure TiO₂, was verified by the increased Zeta potential value, from -22 ζ/㎷ for pure TiO₂ to -47 ζ/㎷ for the silica-coated TiO₂, at pH 7 as measured using a Zeta potential analyzer.