Recent progress in nickel oxide-based chemiresistive toxic-gas sensors

Continuous advancements in technology and industry have resulted in the discharge of toxic and hazardous gases that pose a threat to human health and the environment. Consequently, developing gas-sensing devices with high sensitivities and selectivities toward these gases is crucial. In recent years, interest in sensors for gases based on p-type nickel oxide (NiO) materials has increased owing to their good catalytic activity, outstanding repeatability, high availability, excellent affordability, good sensing properties, and environmental friendliness. This review presents the synthesis, morphology-dependent sensing behaviors, and applications in enhanced gas-sensing devices of NiO nanostructures. Additionally, the impact of several strategies, including doping and functionalization of NiO-based sensors, on their gas-sensing behavior is discussed. Soon, these gas-sensing instruments are expected to play a crucial role in environmental monitoring, chemical process control, personal safety, and other areas because of their promising properties, which are superior to those of conventional methods, and their ability to identify harmful gases and volatile organic compounds. Building on previous studies on various synthesis methods and sensing enhancement strategies, we present a review of NiO-based chemiresistive sensors for toxic gas detection.