Hydrothermal synthesis and NH₃ gas sensing property of WO₃ nanorods at low temperature

One-dimensional self-assembled single-crystalline hexagonal tungsten trioxide (WO₃) nanostructures were synthesized by wet chemical-assisted hydrothermal processing at 120 °C for 24 h using sodium tungstate and hydrochloric acid. Urchin-like hierarchical nanorods (petal size: ∼16 nm diameter and 110 nm length) were obtained. The samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray diffraction. Sensors based on WO₃ nanorods were fabricated by coating them on SiO₂/Si substrate attached with Pt interdigitated electrodes. NH₃ gas-sensing properties of WO₃ nanorods were measured at different temperatures ranging from 50 °C to 350 °C and the response was evaluated as a function of ammonia gas concentration. The gas-sensing results reveal that WO₃ nanorods sensor exhibits high sensitivity and selectivity to NH₃ at low operating temperature (50 °C). The maximum response reached at 50 °C was 192 for 250 ppm NH₃, with response and recovery times of 10 min and 2 min, respectively. (paper)