Ultrahigh sensitive NO sensor based on WO3 film with ppb-level sensitivity

Nitric oxide (NO) is one of the hazardous gases which directly affect the vital organs of human beings. An accurate identification is essential for air quality assurance, environmental monitoring, automotive technology, and other industrial processes. Herein, we report nanostructured tungsten oxide (WO₃) thin-film grown on SiO₂ substrate under controlled oxidation conditions for NO sensing. The nanostructured-WO₃ film's monoclinic phase has an average crystallite size of 12.89 nm, a lattice strain of 20.56, and an optical band gap of 2.89 eV. The fabricated device demonstrates high selectivity, stability, and faster response/recovery time with a sensor response of 1.26 for 100 ppb NO concentration, which increases to an ultra-high response (>25) for 1 ppm at 250 °C with a detection limit of ～4 ppb. Ultrahigh response of the sensors is due to high specific surface area and effective gas diffusion ability, which lead to potential applications in low concentration NO detection.