Titanium Oxide Nanoparticles Precipitated from Low‐Temperature Aqueous Solutions: I. Nucleation, Growth, and Aggregation

Abstract

Titanium oxide (TiO 2 ) thin films can be prepared by controlled hydrolysis of a titanium tetrachloride (TiCl 4 ) precursor in an aqueous solution at temperatures below 100°C. As part of an effort to understand the formation of such TiO 2 films, the kinetics of the nucleation, growth, and aggregation of TiO 2 nanoparticles in aqueous solutions of TiCl 4 were studied using dynamic light scattering and a transmission electron microscope (TEM). A higher degree of supersaturation, produced by a higher solution temperature, a higher concentration of TiCl 4 , or a higher pH, results in a shorter nucleation induction time, a faster initial growth/aggregation rate, and a larger aggregate size. The interfacial energy of TiO 2 nanoparticles was found to be 0.072 J/m 2 from the homogeneous nucleation theory. Further investigations by a high‐resolution scanning electron microscope (SEM) and TEM for the as‐deposited films showed the structure hierarchy organized from nanocrystalline particles precipitated in the supersaturated solution. As a result, the effect of solution conditions on the nucleation, growth, and aggregation of TiO 2 nanoparticles can provide useful guidance for tailoring of microstructures of the TiO 2 films.