Growth Mechanism of Nano-sized Titania-coated Silica Particles Prepared from Metal Alkoxide in a Nonionic Water-in-Oil Microemulsion

Abstract

Nielsen's chronomal analysis was applied to clarify the growth mechanism of TiO2 particles coated on SiO2 core nanoparticles. In this study, SiO2 nanoparticles and TiO2-coated SiO2 nanoparticles were synthesized by the hydrolysis of TEOS and TEOT, respectively, using a water-in-oil (W/O)-type microemulsion method. Firstly, SiO2 nanoparticles 17-nm size were obtained by controlled hydrolysis of TEOS solutions, and then the SiO2 particles in the microemulsion were allowed to coat and grow by the further addition of TEOT as a precursor of the TiO2 particles. Considering the chronomal analysis, it was assumed that the particle growth mechanism was a surface reaction in which the rate-limiting step was a first-order polynuclear layer growth mechanism and the growth rate constant, kp, was about 6.06X10-8 cm/sec.