Fabrication and photoluminescence of rutile-TiO₂ nanorods

Densely assembled single-phase rutile-TiO₂ nanorods with diameters of 150-200 nm and lengths of 2-7 μm have been successfully synthesized for the first time by a heating-sol-gel template method. It was found that the heating process of TiO₂ sol was beneficial to the single-phase formation of rutile-TiO₂ nanorods. Transmission electron microscopic observations reveal that these rutile-TiO₂ nanorods are the aggregates of nanocrystallites grown preferentially to the [110] axis with diameters of 10-30 nm. Selected area electron diffraction and energy dispersive X-ray spectroscopy measurements confirm that the obtained nanorods are rutile-TiO₂ nanorods with good compositional uniformity and a relatively distinct crystallite shape over the entire length. The photoluminescence result shows a broad band confined in the wavelength range of 400-600 nm. This broad band is thought to originate from bound excitations emission due to the trapping of free excitons by TiO₆ octahedra near defects which are possibly oxygen vacancies and/or the color center of Al ³⁺ impurities.