Direct preparation of anatase TiO2 nanotubes in porous alumina membranes

Anodically grown alumina porous membranes have been used as templates for preparing nanoscale materials. Preparation of crystalline metal oxides in the nanopores of the membranes is difficult using conventional methods. A direct deposition technique is desirable for preparing clearly shaped nanotubes consisting of crystalline metal oxides. Monodisperse hollow nanocylinders consisting of crystalline TiO2 particles were directly prepared in a porous Al2O3 membrane by a deposition technique using an aqueous solution of titanium tetrafluoride. The channel diameter was varied in the range 50-150 nm as a function of the deposition time. The walls of the tubes were shown to have nanopores of less than 10 nm. The morphology of the anatase nanotubes is highly controllable because no annealing for crystallisation is required. The bimodal pores of the nanotubes are extremely useful for various photocatalytic gas reactions and for filtration. 16 refs.