NANO LETTERS
Electrochemically Induced Sol−Gel Preparation of Single-Crystalline TiO2 Nanowires
2002 Vol. 2, No. 7 717-720
Zheng Miao, Dongsheng Xu,* Jianhua Ouyang, Guolin Guo,* Xinsheng Zhao, and Youqi Tang State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking UniVersity, Beijing 100871, P. R. China Received March 4, 2002; Revised Manuscript Received April 29, 2002
ABSTRACT Highly ordered TiO2 single-crystalline nanowire arrays have been fabricated within the pores of anodic aluminum oxide (AAO) template by a cathodically induced sol−gel method. Raman spectra confirmed that the nanowires are composed of pure anatase TiO2. TEM investigations indicated that these nanowires have a uniform tetragonal single-crystal structure. Finally, a possible growth mechanism of the TiO2 nanowires is discussed.
Over the past decade, the synthesis and functionalization of one-dimensional nanostructural materials has become one of the most highly energized research areas.1-11 Among the many methods that have been used to prepare such materials, the sol-gel template synthesis method is one of the most common techniques used, especially in the synthesis of semiconductor oxide nanowires. Nanostructures (nanowires and nanotubules) of TiO2,12-14 CdS,15 SiO2,12,16 In2O3,17 Ga2O3,17 V2O5,12 MnO2,12 WO3,12 and many other semiconductor materials have been synthesized using such a solgel template synthesis strategy. However, as was mentioned in a recent report18 by Limmer et al., there are some potential limitations to this technique. For example, since the only driving force of this technique is capillary action, for the sol with higher concentration, filling the pores is difficult (at the same time destabilization of the sol remains a big problem), but low concentration leads to nanomaterials with serious shrinkage and cracking. Electrophoretic growth of nanorods throws some light on how to overcome the limitations of the direct sol filling method.18 While using this sol-gel electrophoresis in the templateassisted growth of nanorods, an electric field was applied to draw the charged sol nanoclusters into the template pores. This procedure failed to synthesize nanorodes of
