The nanocrystalline anatase TiO2, which was synthesized by a sol-hydrothermal process in advance, has successfully modified with cetyltrimethylammonium bromide (CTAB) in the acidic condition as well as in the basic condition. On the basis of the measurements of infrared spectrum and X-ray photoelectron spectroscopy of the resulting TiO2, together with the phase-transfer experiments, it is suggested that the modification mechanism in the acidic condition is closely related to Br-. Interestingly, compared with un-modified TiO2, the modified TiO2 exhibits high photocatalytic activity for degrading Rhodamine B (RhB) solution, especially for that modified in the acid. The enhanced photocatalytic activity of modified TiO2 in the acid is attributed to the role that the Br- can easily capture photo-induced holes and then form active Br, consequently effectively inducing photocatalytic oxidation reactions, based on the surface photovoltage responses of the resulting TiO2. After that, a one-pot sol-hydrothermal route at the temperature as low as 80 degrees C is developed to directly synthesize CTAB-modified nanocrystalline TiO2 with a little preferred growth along < 001 > direction, which can be easily dispersed in the organic system and possess good photocatalytic performance. This work provides a feasible strategy to further improve the photocatalytic performance of nanocrystalline anatase and to synthesize TiO2 nanocrystals with preferential growth. (C) 2010 Elsevier B. V. All rights reserved.