The growth kinetics of TiO2 nanoparticles from titanium(IV) alkoxide at high water/titanium ratio

We report on the growth kinetics of TiO2 nanoparticles synthesized from aqueous solution using titanium(IV) isopropoxide as precursor. The radius of primary particles was found to be between 1.5 and 8 nm, and the average particle radius cubed is shown to increase linearly with time in agreement with the Lifshitz-Slyozov-Wagner model for coarsening. The rate constant for coarsening increases with temperature due to the temperature dependence of the viscosity of the solution and the equilibrium solubility of TiO2. At longer times and higher temperatures, secondary particles formed by epitaxial self-assembly of primary particles were observed with high-resolution transmission electron microscopy. The number of primary particles per secondary particle increases with time, and the percentage of primary particles present in the colloid decreases with increasing temperature.