WO₃ and WO₃-SnO₂ Composite-Based Sensors for Low-Temperature Detection of NO₂ Gas

Air pollution, along with climate change, poses significant risks to human health. One of the major contributors to air pollution, particularly in urban areas, is nitrogen dioxide (NO₂). Continuous real-time monitoring of NO₂ is necessary for the protection of human health and the environment. Currently, efforts are concentrated across the globe toward the development of compact NO₂ sensors that exhibit higher responses at lower operating temperatures. In the present work, conductometric gas sensors based on tungsten trioxide (WO₃), tin oxide (SnO₂), and tin oxide–tungsten trioxide (WO₃-SnO₂) composites have been developed using the chemical solution deposition (CSD) technique for NO₂ detection. The investigation of the sensing response was conducted over a range of temperatures, spanning from 30°C to 180°C towards 10 ppm of NO₂. The pristine WO₃ sensor showed a maximum response of ~ 535 at 150°C with a response time of 21 s and recovery time of 126 s, whereas the WO₃-SnO₂ composite sensor showed a maximum response of ~ 209 at a relatively lower temperature of 120°C with a response time of 37 s and recovery time of 135 s. The composite sensor thus shows the potential for the realization of an efficient NO₂ sensor at a lower operating temperature.