Sonochemical synthesis of nanocrystalline TiO2 by hydrolysis of titanium alkoxides

Nanocrystalline TiO2 has been studied extensively in recent years as photocatalysts to deal with environmental pollutions, such as water purification, wastewater treatment and air purification. Here a novel sonochemical method for directly preparing anatase nanocrystalline TiO2 lias been established. Nanocrystalline TiO2 were synthesized by the hydrolysis of titanium tetrabutyl in the presence of water and ethanol under a high-intensity ultrasonic irradiation(20 kHz, 100 W/cm(2)) at 363 K for 3 h. The structure and particle sizes of the product were dependent upon the reaction temperature, the acidity of the medium and the reaction time. Characterization was accomplished by using various different techniques, such as powder X-ray diffraction (XRD), transmission electron microscopy(TEM), thermogravimetry-differential thermal analysis (TG-DTA) and Fourier transform infrared ( FTIR) spectroscopy. The TEM images showed that the particles of TiO2 were columnar in shape and the average sizes were ca. 3 nm X 7 nm. The formation mechanism of nanocrystalline TiO, under a high-intensity ultrasonic irradiation was also investigated. The hydrolytic species of titanium tetrabutyl in water condensed to form a large number of tiny get nuclei which aggregated to form larger clusters. Ultrasound irradiation generated a lot of local hot spots within the gel and the crystal structural unit was formed near the hot spots with the decrease of the gel nuclei, which lead to form nanocrystal particles.