Enhanced propanol gas sensing performance of p-type NiO gas sensor induced by exceptionally large surface area and crystallinity

Real-time detection of n-propanol vapour is important in human health protection. Thus, we report on the influence of large surface area and crystallinity of p-type NiO nanostructures on propanol sensing characteristics. Structural properties of p-type NiO were investigated by using an X-ray diffractometer and the morphology was analysed by scanning electron microscopy. A Brunauer-Emmett-Teller confirmed the surface area and porosity of the NiO nanostructures. The elemental composition and existences of potential defects were investigated by X-ray photoelectron spectroscopy and photoluminescence, respectively. A systematic comparison study was performed on the annealed nanostructures prepared by hexamethylenetetramine and urea precursors by subjecting all the sensors to volatile organic compounds like ethanol, propanol, toluene, and other reducing and oxidizing gases like methane and nitrogen dioxide using different controlled gas concentrations and operating temperatures. The NiO based sensor derived from the urea precursor and calcined at 400 °C, exhibited a significantly improved sensing response (Ra/Rg ratio of 1.59), higher sensitivity (0.02 ppm−1), ultra-low theoretical detection limit (20 ppb) and excellent selectivity towards 60 ppm propanol vapour Additionally, the fundamental sensing mechanism was elucidated. The high sensitivity and selectivity of NiO based sensors for the detection of propanol is promising.