Nanosized titania particles, with typical particle sizes in the range of 30-50 nm have been synthesized using a microemulsion-mediated process. In this process, the aqueous cores of microemulsions have been used as constrained microreactors for the precipitation of titania precursor. The microemulsion was provided by a functionalized surfactant derived from the commercially available mixtures of sorbitol monooleate and polysorbate 80 (abbreviated as Span-Tween 80). The hydroxide particles, produced by the hydrolysis of the titanium tetraisopropoxide in the water droplets containing surfactant, were separated, dried, and calcined to form nanoparticles of TiO2. The dependence of the size of the precipitated TiO2 particles on various structure parameters of the microemulsion was studied in detail. (C) 2002 Elsevier Science Ltd. All rights reserved.