Formation and Characterization of TiO2-coated SiO2 Nanoparticles by W/O Microemulsion Method

Abstract

Monodisperse, spherical TiO2-coated SiO2 nanoparticles were synthesized using a Water-in-Oil (W/O) microemulsion method. In this process, SiO2 nanoparticles, which act as carrier particles for the coating, were also prepared by a microemulsion method. The mean size of the SiO2 nanoparticles was 20 nm. The reaction parameters were the concentration of tetraethylorthotitanate (TEOT), the feed rate of the starting solutions (TEOT + NP-5 + cyclohexane), the pH, and the reaction temperature. We found that the particle size decreased upon decreasing the TEOT concentration and the feed rate. In addition, it was advisable to maintain the reaction temperature and pH at 15 ℃ and 4, respectively. Consequently, the optimal conditions for the preparation of TiO2-coated SiO2 nanoparticles having narrow particle size distribution were a TEOT concentration of 0.03 ~ 0.04 M, a feed rate of 1.3 ~ 1.5 mL/min, a reaction temperature of 15 ~ 18 ℃, and a pH 4 ~ 5.