A review on recent developments and advances in environmental gas sensors to monitor toxic gas pollutants

Abstract

Air pollutants originating from various sources like vehicular emission, power stations, factories, refineries, industrial emissions, and burning of garbage in open and laboratories, include many toxic gases and pollutants like hydrogen chloride (HCl), hydrogen sulfide (H2S), and volatile organic compounds (VOCs) like benzene, toluene, xylene, and so on, ammonia (NH3), carbon-monoxide (CO), carbon-dioxide (CO2) and nitrogen oxides (NOx), and so on, that are constantly released into the atmosphere and continuously deteriorating our natural environment and surroundings. These pollutants create harmful effects on the ecosystem and affect human health. Though there are many devices available for monitoring these pollutants and toxic gases, they are very expensive and time-consuming. Since the safety of the life of human health, plants, animals, and their surrounding area on topmost priority, thus there is a significant need to develop user-friendly and environmentally friendly sensing devices for real-time monitoring of air pollutant emissions, which are extremely hazardous to the environment, breathable air, and human health. Extensive research has been made by researchers to develop an ideal sensor suitable for the environment and which can be within the reach of the masses. This review article presents different types of gas sensors and the technologies on which they work upon. We have also discussed the different gas sensors with their principle of operation. The working, advantages, and disadvantages of each type of sensor have also been discussed and compared with each other. Despite extensive research over several years to develop a highly sensitive, selective, and quick response sensor for the detection of flammable and toxic gases, the future scope and perspective for scientists are also proposed at the end of this article.