Formation of Nanotubule, Nanorod and Polycrystalline Nanoparticles TiO₂ by Alkaline Hydrothermal Transformation of Anatase TiO₂

Nanostructured titanium oxides with various morphologies were prepared through the hydrothermal treatment of TiO₂ anatase, using LiOH, NaOH and KOH as a peptizing agent at 400 K for 30 hrs. The obtained samples were characterized using the scanning electron microscopy, transmission electron microscopy, X-ray diffraction, BET measurement and the electron spin resonance spectroscopy. The observed morphologies such as tubule, partially plugged nanorod and polycrystalline nanoparticles can be tailored depending on the types of alkali metal ion, Na⁺, K⁺, and Li⁺ used in the hydrothermal treatments. The result of the ESR studies suggested the existence of paramagnetic sites on the annealed nanostructured TiO₂ samples. The ESR signals came from the single electron trapped in oxygen vacancy (SETOV) and Ti³⁺.