Self-assembly of rutile (α-TiO2) nanoclusters into nanorods in microemulsions at low temperature and their photocatalytic performance

A novel method – inverse microemulsion has been developed not only for synthesizing low cost TiO₂ nanocrystals but also for the first time making these nanocrystals self-assemble into various nanoparticles at 85°C. By variation of the volume ratios of oil to water in reverse microemulsions, the morphologies of obtained samples turned from nanoclusters to nanospherules, then grew into nanodumbbells, and became nanorods at last. It could be observed by transmission electron microscope (TEM) directly. The resulting materials were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM). The photocatalytic activity of TiO₂ was tested with photodegradation of Methyl Orange (MO) in water. The catalyst consisting of nanorods showed the highest photocatalytic activity, which is due to its large surface area. Furthermore, the mechanism of self-assembly of TiO₂ nanocrystals was discussed in detail.