Large-Scale Hydrothermal Synthesis of Tungsten Trioxide Nanowires and Their Gas Sensing Properties

摘要

Large scale polycrystalline nanowires of hexagonal tungsten trioxide were successfully prepared by a simple hydrothermal method. The crystal structure and morphology were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscope (HRTEM). Uniform hexagonal WO{sub}3 nanowires were obtained with diameter of about 6-15 nm and length of up to several micrometers. Thick-film gas sensors based on hexagonal WO{sub}3 nanowires were fabricated by screen-printing technology. CO and NH{sub}3 sensing properties at low concentrations (5-100 ppm) were investigated. It was found that the obtained sensing films exhibited excellent CO and NH{sub}3 gas response between 250℃ and 350℃. Sensitivities (R{sub}a/R{sub}g) measured between 250℃ and 350℃ for 5-100 ppm CO and NH{sub}3 ranged from 4 to 145. Response time of the sensor was less than 5 seconds. Sensitivities increased almost linearly with increasing concentrations of CO and NH{sub}3. The reaction paths that explain the sensitivity changes to CO and NH{sub}3 were discussed in detail.