Template-based, near-ambient synthesis of crystalline metal-oxide nanotubes, nanowires and coaxial nanotubes

In response to a growing need for metal-oxide nanotubes and nanowires for nanoelectronic applications and size-effect studies, crystalline nanotubes and nanowires in a range of metal oxides have been synthesized at near-ambient conditions and without the application of beat treatments, pressure or an external electric field. Specifically, the mechanisms of formation of crystalline TiO2 nanotubes and nanowires from flourine-based liquid precursors inside anodic aluminum oxide templates have been elucidated. This method can be extended to synthesizing nanotubes/nanowires of other crystalline metal oxides, such as ZrO2, SnO2 and FeOOH. Using sequential deposition, TiO2/ZrO2, coaxial nanotubes have been synthesized. In principle, the methods outlined here could be used to fabricate crystalline nanotubes and nanowires of tailored dimensions in other metal oxides. The ability to synthesize, at near-ambient conditions, crystalline metal-oxide nanotubes and nanowires of tailored geometries represents a clear advantage in terms of minimal equipment requirements, low cost and possible incorporation of biomolecules and temperature-sensitive moieties. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.