The deposition of titania nanoparticles on spherical silica

초록

The deposition of titania (TiO2) nanoparticles on monodisperse silica (SiO2) spheres was carried out through a sol-gel process. The TiO2 nano sols were obtained by peptization (the process of redispersing a coagulated colloid) and were deposited on SiO2 particles with the variation of TiO2/SiO2 weight ratio and pH of the mixture in an aqueous solution. Titania sols were not deposited on silica surfaces in their stable pH region (< pH 2). However, they reacted with silica surface and thus formed coated-particles, as pH value increased to an unstable region of sols. In order to obtain well-coated particles and prevent titania from the formation of self-condensed pure titania particles, the difference in zeta-potentials between silica and titania should be maximized. At pH 4.5, the difference in zeta-potentials between silica and titania maximized and titania-coated silica particles with highest titania contents (~ 20%) were obtained without the self-aggregation. The morphologies of particles were characterized with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The isoelectric points (IEP) of particles were measured with zeta-potential analyzer.