Fabrication of double-walled TiO2 nanotubes with bamboo morphology via one-step alternating voltage anodization

Ordered arrays of TiO2 nanotubes with double-walled structures and bamboo-like morphologies were prepared by a one-step titanium foil anodic oxidation using a solution of NH4F and ethylene glycol as electrolyte. The as-prepared titania nanotubes exhibit double-wall morphology even prior to the heat treatment process. Field emission-scanning electron microscopy (FE-SEM), X-ray powder diffractometry (XRD) and Raman spectroscopy were used to investigate the structure and morphology of the obtained TiO2 nanotubes. The current-versus-time curves were recorded to monitor the anodization process. Structural investigations of the obtained nanotubes revealed the presence of pure anatase phase TiO2 after annealing at 500 degrees C, as confirmed by XRD and Raman spectroscopy measurements. By optimizing the electrochemical anodization conditions, TiO2 nanotubes with tunable structures can be reproducibly prepared. (C) 2011 Elsevier B.V. All rights reserved.