Formation and optical properties of pure nano-sized anatase titania by low-temperature aqueous sol-gel route

Nanocrystalline anatase titania particles were synthesized by low-temperature aqueous sol-gel transformations from new types of precursors [Ti{OPrⁱ}₄] (A), [{acac}₂Ti{OPrⁱ}{ONC₉H₆}] (1), and [{acac}₂Ti{ONC₉H₆}₂] (2) {where, ONC₉H₆ = 8-hydroxyquinoline}. Formation of all the precursors was confirmed by elemental analysis, molecular weight measurements, FTIR, and NMR (¹H and ¹³C). Titania samples (a), (b), and (c) were formed by aqueous sol-gel transformations of (A), (1), and (2), respectively. The resulting nano-materials were characterized using XRD, TEM, SEM, EDX, SAED, FTIR, and UV-Visible spectroscopic techniques. From the X-ray pattern, the phase purity of the synthesized powders was confirmed as anatase TiO₂. Crystallite size of all the oxide samples was measured by XRD and TEM, found to be 26 nm (a), 11 nm (b), and 8 nm (c). Surface morphologies of all the samples were evaluated by SEM. Selected area diffraction (SAED) of (b) and (c) are also corroborated the XRD results. The absorption spectra of oxide samples, (a), (b), and (c) show energy band gap of 2.9 eV, 3 eV, and 3.1 eV, respectively. SAED-EDX analysis confirmed the formation of pure anatase-phase titania nanoparticles.