Effect of Plasma on Liquid Surface on an Aqueous Dispersion of Titanium Dioxide Nanoparticles

Abstract

Titanium dioxide (TiO₂) nanoparticles have been used in sunscreen cosmetics for ultraviolet (UV) light protection. However, nanoparticles of TiO₂ tend to form aggregates in aqueous dispersions because of their high surface energy. Therefore, it is important to stably disperse TiO₂ nanoparticles in the aqueous solutions in order to enhance the efficient UV protection properties of TiO₂. In this study, we tried to prepare aqueous dispersions of TiO₂ nanoparticles by using plasma on liqid surface which is generated by applying high voltage between the tip of a needle electrode in the gas phase and the liquid surface.The decreases of average particle size of TiO₂ in the dispersions with the plasma treatments in air and Ar atmosphere were confirmed by dynamic light scattering measurements. With the plasma treatment, isotropic point for TiO₂ particles increased from 5.4 (without plasma treatment) to 9.3 (with plasma treatment in air) and 8.0 (with plasma treatment in Ar atmosphere). Futhermore, these fine dispersions showed higher UV protection properties compared to the dispersions prepared by only sonication.These facts suggest that the application of plasma on liquid surface is a new method for preparing stable nanoparticle dispersions.