A panoramic view of NOx and NH3 gas sensors

The alarming growth in air pollution has drawn more attention to gas sensing technologies. As a result, the fabrication of highly sensitive and selective gas sensors has become a hot research topic and hence researchers all over the world are investigating gas sensors and electronic noses. The several state-of-the-art nanomaterials for ammonia and NOX gas detection are well described in this review, including metal oxide semiconductors, conducting polymers, metal organic frameworks, transition metal dichalcogenides, carbon-based materials and so on. The effects of morphological control, annealing temperature, film thickness, doping, functionalization, etc. on the gas sensing performance are examined in detail. This paper also focuses on the promising ideas of flexible and smart sensors that will contribute to further development in this field. Finally, this review is concluded with a discussion of the limitations of the currently available materials as well as opportunities for future development.