Microstructure and formation mechanism of titanium dioxide nanotubes

Titanium dioxide nanotubes are synthesized using sol–gel method. Electron energy-loss spectroscopy has been used to investigate the chemical composition of the nanotubes. The results show that the atomic ratio of O/Ti is very close to two. Electron diffraction studies indicate that the nanotubes have the anatase structure. High-resolution transmission electron microscopy studies show that the nanotubes possess a layered structure with layer spacing of about 7.1 Å. The tube axis is determined to be along [0 1 0] direction of the anatase phase. The formation mechanism of the nanotubes can be explained as 3D→2D→1D. The two-dimensional lamellar TiO2 is essential for the formation of the nanotubes.