Low-temperature synthesis of highly crystalline TiO₂ nanocrystals and their application to photocatalysis

Synthesis of highly crystalline TiO₂ nanocrystals with various shapes and crystal structures from controlled aqueous sol-gel reactions at room temperature was investigated. The HRTEM image of these nanorods showed zigzag surface features with the [001] direction of the anatase being parallel to the long axis of the nanorods, which is very similar to the characteristics of the anatase nanorods. The BET surface areas of the spherical anatase nanocrystals, anatase nanorods, and rutile nanorods were found to be different in all the three. TiO₂ nanocrystals with mixed crystal structures and various shapes were generated in the absence of the P-123 polymer. The results demonstrated that the presence of salt or acid was essential to synthesize the TiO₂ nanocrystals with unique shapes and crystal structures and the P-123 controls the hydrolysis and condensation of the titanium tetraisopropoxide precursor.