Characteristics of silica-coated TiO2 and its UV absorption for sunscreen cosmetic applications

Nanosized TiO2 is used extensively in sunscreen cosmetics as an inorganic UV absorber that can allow an optically transparent film to be applied to human skin. TiO2 is known to exist in three crystal forms: anatase, brookite and rutile. The rutile phase is generally used as a component in sunscreen cosmetics because of its higher UV absorption. A surface coating can be added to nanosized TiO2 to enhance its UV absorption by a different light diffraction mechanism. Silica-coated nanosized TiO2 is examined in this study for this purpose. The nanosized TiO2 has been synthesized using hydrolysis of tetra-isopropylorthotitanate (TIPT) as a precursor. After a calcination process, nanosized TiO2 was formed and subsequently its surface modified by coating with tetraethoxysilane (TEOS) as the source of the silica. The same coating method was applied to nanosized commercial TiO2, to compare the surface characteristics. The resulting powders of coated TiO2 were examined by transmission electron microscopy (TEM) and analyzed by energy dispersive analysis (EDS), respectively. UV-vis spectroscopy was used to study the differences and effectiveness of the coated and uncoated TiO2. Copyright (C) 2006 John Wiley & Sons, Ltd.