Direct conversion of TiO2 sol to nanocrystalline anatase at 85 °C

Nanocrystalline TiO2 anatase with particle size in the range of 5-7 nm has been prepared by in situ cracking of the sol at 85 degreesC, thereby avoiding the intermediate gel formation process. Hydrolysis of Ti(O-isoPr)(4) was carried out in excess of 2-propanol to keep the suspension of fine particles from agglomeration. Differential thermal analysis, thermogravimetric analysis, differential scanning calorimetry, powder x-ray diffraction (XRD), and electron microscopy have been used to characterize the samples. Gel to crystalline conversion, which requires a temperature of at least 400 degreesC, can be achieved by digesting the TiO2 sol at 85 degreesC. XRD and selected area electron diffraction patterns show the presence of a small amount of brookite phase along with the major anatase phase. High-resolution transmission electron microscopy shows that the average grain size of TiO2 particle remains around 5-9 nm even when heated at 510 degreesC.