液面プラズマ処理による微粒子酸化チタンの高分散化

抄録

Titanium dioxide (TiO₂) nanoparticles have been used as a cosmetic material for UV protection. Due to their high surface energy, they aggregate particularly under neutral to weakly acidic conditions close to their isoelectric point (5.6). In order to enhance UV protection properties in cosmetic materials, it is important to improve the particle dispersibility under neutral condition. In this study, plasma was generated between the liquid surface of TiO₂ nanoparticle suspension and a needle electrode in the gas phase. As a result, the surface of TiO₂ nanoparticles were coated with amorphous silica by using silicon wafer as an underwater electrode. Since the isoelectric point of the silica-coated TiO₂ nanoparticles was lowered to 4.7, the electrostatic repulsion between the particles was increased under neutral condition resulting in improved particle dispersibility. The silica-coated TiO₂ nanoparticles are expected to be applied to lotions and sunscreens with higher transparency and UV protection.