Abstract

Uniform anatase-type ellipsoidal TiO2 nanoparticles have been prepared by phase transformation of a Ti(OH)4 gel matrix in the presence of sodium acetate as a shape controller. Sodium acetate was found to modify the TiO2 particle shape from cube to ellipsoid in the alkaline solution with the concentration varying from 0 to 0.50 M. A significant reduction of the formation rate of the anatase TiO2 was found due to the adsorption of sodium acetate on their surfaces. Then, the formation of TiO2 nanoparticles could be promoted by the added seeds and the seeding effect also revealed that the particle size could be controlled. Moreover, the results of seeding experiment suggested that the rate-determining step of the gel-sol process was not the dissolution of the hydroxide gel, but the deposition of the monomeric solute onto the preformed particles. Additionally, based on the adsorption experimental results of sodium acetate on the ellipsoidal and cubic particles, the shape transition may be explained in terms of the preferential adsorption of acetate ions onto the specific planes parallel to the c-axis of the tetragonal system and then inhibiting the growth of these planes.

Keywords: Titania, shape control, sodium acetate, adsorption, seeding