A sonochemical method was developed for the fabrication of novel square-shaped TiO2 nanocrystals doped with different F contents. The prepared samples were characterized by some physicochemical characterizations like X-ray diffraction (XRD). N-2 physical adsorption, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy and UV-vis diffuse reflectance spectra (DRS). Phenol, as a hazardous chemical in water, was chosen to evaluate the photocatalytic degradation performance of the prepared TiO2 nanocrystals under UV light irradiation. Results show that under ultrasonic irradiation conditions. F can easily be doped into TiO2 and the obtained pure and F doped TiO2 nanocrystals show mesoporous structures which were formed by the role of ultrasound-induced aggregation. Moreover, the doping of optimal content of F (1.3 mol%) gives 5.3 times increase in the phenol degradation rate. The high photocatalytic degradation activity of the doped TiO2 could be attributed to the factor that F doping increases the surface hydroxyl groups over TiO2 and effectively reduces the recombination rate of photo-generated electron/hole pairs, then producing more (OH)-O-center dot radicals to decompose the phenol molecules. (c) 2012 Elsevier B.V. All rights reserved.