Synthesis of metal and metal oxide nanostructures and their application for gas sensing

A method has been developed to synthesize metal and metal oxide nanostructures in high yields on the surface of SiO2/Si substrate. In this method, starting materials in a covered alumina crucible are thermally evaporated under a high vacuum or a low pressure of ambient air. Spherical gold nanoparticles with a size of 15 nm and nanowires with a diameter of 70 nm were synthesized. SnO2 rough microwires, smooth nanowires, and nanoknives were synthesized by using Sn granules, SnO powder, and SnO2 powder as source materials, respectively. The microwires showed a quadrangular cross section and a length of several microns, while the nanowires showed a circular cross section and approximately the same length. The effects of source temperature and deposition time on nanostructure growth were studied. X-ray diffraction patterns suggested that the as-synthesized products consisted of crystalline nanostructure. Nanocomposite gas sensors on the base of noble metal and metal oxide were fabricated. These SnO2 nanowire gas sensors showed a reversible response to dilute NO2 gas at operating temperatures ranging between room temperature and 300 °C even at high concentrations. The results demonstrated that gold doping improved the sensor response.