Titania nanotubes prepared by chemical processing

We report a new method for the synthesis of titanium oxide (TiO₂) nanotubes. When anatase-phase- or rutile-phase-containing TiO₂ was treated with an aqueous solution of 5-10 M NaOH for 20 h at 110 °C and then with HCl aqueous solution and distilled water, needle-shaped TiO₂ products were obtained (diameter ≈8 nm, length ≈100 nm). The needle-shaped products are nanotubes with inner diameters of approximately 5 nm and outer diameters of approximately 8 nm. The formation mechanism of titania nanotubes is discussed in terms of the detailed observation of the products by transmission electron microscopy: the crystalline raw material is first converted to an amorphous product through alkali treatment, and subsequently, titania nanotubes are formed after treatment with distilled water and HCl aqueous solution.