TiO2 nanoparticles were prepared employing forced hydrolysis of titanium tetrachloride in an acid aqueous solution. We observed the highly stable dispersibility of TiO2 nanoparticles calcined at 600 °C and 700 °C in water. X-ray diffraction (XRD) showed that the phase transformation from anatase (A) to rutile (R) occurred when the nanoparticles were calcined over 600 °C. Transmission electron microscope (TEM), Fourier-transform infrared spectroscopy (FT-IR) and Thermo-gravimetric analysis (TGA) showed that the phase transformation led to the formation of the better spherical particlesis, which were in favour of water adsorption onto the surface of the TiO2. The Brunauer–Emmett–Teller (BET) data of particles calcined at different temperatures showed that the surface hydration forces impeded TiO2 particles aggregation and resulted in the high structural stability during A–R phases transformation. Zeta potentials of TiO2 nanoparticles calcined at different temperature showed the electrostatic forces were not crucial factors in the stable dispersibility. A model illustrated that the spherical particles of TiO2 allowed maintaining the high density of water on the surface of TiO2 nanoparticles. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)