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.