Size-effects in TiO2 nanotubes: Diameter dependent anatase/rutile stabilization

In the present work we demonstrate that amorphous anodic TiO2 nanotubes show upon annealing a tube diameter dependent phase stabilization. For tube diameters <30 rim the formation of ruffle is observed while for larger diameters anatase is formed. This effect is induced by the presence of the metallic substrate-in its absence all tube diameters are converted to anatase. As the nature of the stable phase strongly affects electronic, optical and biomedical properties of TiO2, the finding is of a high significance for many applications of TiO2 nanotubes. (C) 2011 Elsevier B.V. All rights reserved.