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

Titanium oxide (TiO{sub 2}) thin films can be prepared by controlled hydrolysis of a titanium tetrachloride (TiCl{sub 4}) precursor in an aqueous solution at temperatures below 100 C. As part of an effort to understand the formation of such TiO{sub 2} films, the kinetics of the nucleation, growth, and aggregation of TiO{sub 2} nanoparticles in aqueous solutions of TiCl{sub 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{sub 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{sub 2} nanoparticles was found to be 0.072 J/m{sup 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{sub 2} nanoparticles can provide useful guidance for tailoring of microstructures of the TiO{sub 2} films.