Preparation of TiO ₂ nanocrystallite powders coated with 9 mol% ZnO for cosmetic applications in sunscreens

The preparation of TiO ₂ nanocrystallite powders coated with and without 9 mol% ZnO has been studied for cosmetic applications in sunscreens by a co-precipitation process using TiCl ₄ and Zn(NO ₃) ₂·6H ₂O as starting materials. XRD results show that the phases of anatase TiO ₂ and rutile TiO ₂ coexist for precursor powders without added ZnO (T-0Z) and calcined at 523 to 973 K for 2 h. When the T-0Z precursor powders are calcined at 1273 K for 2 h, only the rutile TiO ₂ appears. In addition, when the TiO ₂ precursor powders contain 9 mol% ZnO (T-9Z) are calcined at 873 to 973 K for 2 h, the crystallized samples are composed of the major phase of rutile TiO ₂ and the minor phases of anatase TiO ₂ and Zn ₂Ti ₃O ₈. The analyses of UV/VIS/NIR spectra reveal that the absorption of the T-9Z precursor powders after being calcined has a red-shift effect in the UV range with increasing calcination temperature. Therefore, the TiO ₂ nanocrystallite powders coated with 9 mol% ZnO can be used as the attenuate agent in the UV-A region for cosmetic applications in sunscreens.