A facile hydrothermal method for the controllable synthesis of TiO2 nanocrystals with tunable shapes

The controllable preparation of anatase TiO2 nanocrystals with tunable shapes has drawn much attention recently. The general method used to prepare such nano-TiO2 involves the use of HF as a surfactant. However, the use of HF should be avoided due to its high risk. Therefore, the development of facile and friendly methods to controllably synthesize anatase TiO2 nanocrystals is important. In this research, instead of general titanium precursors, titanium peroxide sol was used as the raw material to synthesize anatase TiO2 nanocrystals due to its high stability in water. Oleic acid and oleylamine were used as capping surfactants. A hydrothermal method, without the use of high risk HF, was developed to prepare uniform anatase TiO2 nanocrystals with various shapes, which can be tuned from octahedral bipyramidal, to truncated octahedral bipyramidal, and then to nano-sheets. The ratio between {001} and {101} surfaces can be easily tuned by changing the amounts of oleic acid and oleylamine used. The photocatalytic activity of these anatase TiO2 nanocrystals was also evaluated through crystal violet photo-degradation under UV light illumination. It was shown that the anatase TiO2 nanocrystals can present a photocatalytic activity comparable to that of commercial P25.