Abstract
New UV-blocking particles consisting of cerium dioxide (CeO2) and amorphous silica (SiO2) were synthesized. When they were incorporated into various cosmetic formulations, these particles showed unique light-scattering/absorbing properties while appearing transparent on the skin. By coating the particles with amorphous SiO2, we were successful in overcoming the high catalytic activity of CeO2. These particles were prepared in an aqueous dispersion system, and after the formation of cerium hydroxide and complexing of sodium silicate, the particles were dried. The shape of these particles is a needle-shape with an average size of about 50nm on the major axis and about 6nm on the minor axis. The optical absorbance of these particles began at 410nm with maximum absorbance at 297nm and they showed much higher transparency in the visible ray region than an equivalent micronized titanium dioxide (TiO2) particle. An inclusion of 20% of these particles in lipstick formulations caused much less color change than a 4% inclusion of micronized TiO2. These new particles can solve the problems encountered in cosmetics by providing high SPF values while maintaining a natural appearance.
