Controlling Phase, Crystallinity, and Morphology of Titania Nanoparticles with Peroxotitanium Complex: Experimental and Theoretical Insights

This Letter presents a detailed experimental and theoretical study to unravel the unique role of hydrogen peroxide in controlling phase and thereby shape and crystallinity of nanocrystalline titania. Analysis of all reaction parameters revealed that the H2O2/Ti ratio (r(p)) is the predominant factor to obtain crystalline titania with different phase composition. Evolution of phase and crystallite size of the materials is determined from X-ray diffraction and Raman spectroscopy. Transmission electron microscopy images showed phase-related morphology, that is truncated anartase and rod-like rutile. The solution Raman and Fourier transform infrared spectroscopy study confirmed different bonding pattern in the reaction medium. Complexation of titanium with -O-O- in bidentate manner with C-2v symmetry in the reaction mixture is confirmed by the strong Raman band at similar to 630 cm(-1). Quantum mechanical calculations are performed using density functional theory with B3LYP/LANL2DZ to provide all possible intermediate sturctures and to predict the probable mechanism leading to the formation of different phases of titania under different experimental conditions.