Water concentration controlled hydrolysis and crystallization in n-octanol to TiO2 nanocrystals with size below 10 nm

Hydrolysis of tetrabutyl titanate (TBT) and crystallization from hydrolyzed intermediates were carried out in a simple ternary system including n-octanol, TBT and water. Anatase TiO2 nanocrystals (NCS) were prepared with precise size control below 10 nm. The hydrolysis rate at different water concentration (Cwater) was evaluated by measuring the induction time before turbidity changing of the synthetic solution. Fourier transform infrared spectrum (FT-IR) and thermogravimetric/differential thermal analysis (TG/DTA) techniques were applied to make clear the composition of hydrolyzed intermediates obtained at different Cwater. Powder X-ray diffraction (XRD) technique was used to track the crystallization process of TiO2 NCS. Transmission electron microscopy (TEM), XRD, FT-IR and TG/DTA techniques were used to characterize the particular properties of NCS. The Cwater controlled mechanism responsible for the slow hydrolysis and crystallization were discussed. Since no other organic capping ligands or rapid injecting techniques were used to limit NCS’ growth and the solvent n-octanol can be easily separated and reused, this simple synthetic process is of green chemistry and has application potential in large-scale preparation of inorganic NCS.