Hydrothermal synthesis, characterization of h-WO₃ nanowires and gas sensing of thin film sensor based on this powder

The monodisperse hexagonal WO₃ (h-WO₃) nanowires were synthesized using hydrothermal treatment through the acidification of Na₂WO₄ · 2H₂O by addition of K₂SO₄ and Na₂SO₄. The obtained products were characterized using X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy. It showed a high crystallinity and good dispersity of nanowire structure with the exposure of < 200 > crystal facets. Based on h-WO₃ products, thin film sensors were prepared. The gas-sensing properties to various concentrations (10, 20, 50, 100, and 200 ppm) of ethanol and formaldehyde were investigated. The h-WO3 nanowires exhibited high responses to both ethanol and formaldehyde gas. The sensor exhibited remarkably good response and fast response/recovery time, which were as short as 6–8 s. A possible reason for the influence of oxide structure on the sensing properties of thin film sensors is proposed. This work shows great potential for the preparation of 1D h-WO₃ nanostructures and their application in the detection of toxic gases. - Highlights: • Monodisperse h-WO₃ nanowires with a diameter of 80 nm were hydrothermally synthesized. • These h-WO₃ nanowires grow along the direction of [001] and with < 200 > facets exposed. • Sensor based on h-WO₃ nanowires show excellent gas sensing properties to toxic gases