Nanocrystalline ceramic materials (semiconducting oxides, SiC, GaN, CNT), due to their excessive surface to volume ratio and large free surface energy, are one of the key focus domains for researchers in the field of chemical sensors during the last decade. Owing to the nanocrystallinity, several promising effects on sensor parameters like operating temperature, responsive magnitude (S), response time, recovery time, and selectivity, have been studied. This article provides a comprehensive review of the current research activities that concentrate on chemical sensors based on nanocrystalline-nanoporous thin films along with the thin films consisting of nanotubes, nanorods, nanobelts, nanoribbons and nanowires, comprising the wide bandgap semiconducting oxides (SnO2, ZnO, TiO2, In2O3 etc) and other ceramic materials such as SiC, GaN, CNT.
