Size-controlled synthesis of spherical TiO2 nanoparticles:: Morphology, crystallization, and phase transition

Obtaining spherical-shaped semiconductor nanoparticles of uniform size is essential for the fabrication of photonic crystals. We report the synthesis of nanometer-size spherical titania particles with narrow size distribution from glycolated precursors. Through controlled hydrolysis of glycolated precursors, particles of 683 to 50 nm average diameters, with narrow size distribution, could be produced for the first time. Effects of air annealing on the morphology, size shrinkage, and phase transition of the nanoparticles are studied by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and high-resolution electron microscopy techniques. Probable mechanisms for formation of titania nanoparticles and their size control are discussed.