Effect of heat treatment on the properties and structure of TiO2 nanotubes: phase composition and chemical composition

Titanium oxide (TiO2) nanotubes prepared by electrolytic anodisation of a titanium electrode have been systematically heat treated to control the conversion of the as-prepared amorphous structure to nanocrystalline anatase and rutile. Raman spectroscopy revealed that the temperature of calcination is critical in determining the structure and crystallinity of the titania. X-ray Photoelectron Spectroscopy analysis shows the as-prepared film to consist mainly of oxide, although a small amount of fluoride contamination remains from the electrolyte. Organic components from post-anodising cleaning treatments were also present. Fluorine ions are gradually ejected from the anodic layer during annealing and the fluorine concentration is negligible in samples that are heat treated above 400 degrees C. Choosing the appropriate annealing temperature allows the structure to be made up of defined proportions of anatase and rutile with a reduced contamination of species from the electrolyte or organic solvents. Copyright (C) 2010 John Wiley & Sons, Ltd.