Preparation and Hydrogen Sensing Properties of ITO Nanotubes by Sol-Gel Method Combined with Porous Anodic Aluminum Oxide Template

Tin-doped indium oxide (ITO) nanotubes were fabricated by means of a simple sol-gel method combined with porous anodic aluminum oxide template. Scanning electron microscopy (SEM), Transmission electron microscopy, HRTEM, and X-ray diffraction were applied to characterize the morphology and structure of the as-prepared nanotubes. The gas sensing properties of the ITO nanotubes to wards H-2 (1000 mu g/g) have been investigated. It has been demonstrated that the as-prepared nanotubes exhibited a polycrystalline microstructure, which are composed of nanoparticles with sizes ranging from 10 to 20 nm. The mean outer diameter of these nanotubes is about 250 nm, corresponding to the diameter of channels in the AAO template and the average thickness of the tube wall is about 25 nm. After postannealing at 550 degrees C, X-ray diffraction pattern indicates that they are of a cubic bixbyite crystal structure and Sn4+ ions were homogeneously doped into the In2O3 crystal lattice. The as-synthesized ITO nanotubes showed excellent gas-sensing properties to H-2 in terms of sensor response and selectivity at room temperature.