Synthesis, characterization and particle size distribution of TiO 2 colloidal nanoparticles

Abstract

Nanoparticles of controlled size, well defined shape, pure phase and of clean surfaces are ideal model systems to investigate surface/interfacial reactions. In this study we have explored the possibility of synthesizing TiO 2 nanoparticles in the size range of 7–20 nm under well controlled experimental conditions. A simple method based on the hydrolysis of TiCl 4 was used to obtain particles having surfaces free from organics. Stable dispersions of TiO 2 nanoparticles of various sizes were obtained by optimizing the reaction/dialysis time and temperature. The synthesized TiO 2 particles were found to be predominantly of anatase phase and narrow particle size distributions were obtained. The TiO 2 particles were characterized with respect to their phase, size and shape by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Particle size distribution in a colloidal dispersion was obtained by the electrospray scanning mobility particle sizer (ES-SMPS) method and compared with an average particle size determined from dynamic light scattering (DLS). The average particle sizes obtained by the DLS and ES-SMPS methods were in good agreement, while a primary particle size of ∼4 nm was found in X-ray diffraction irrespective of the particle size in solution. Early stages of the nucleation process were monitored by the ES-SMPS method. These results show that small particles of 4–5 nm are initially formed and it is highly likely that large particles are formed due to aggregation of primary particles.