A review on recent progress of p-type nickel oxide based gas sensors: Future perspectives

Recently, technological and industrial advances uninterruptedly cause the release of hazardous and toxic gases that are harmful to human life; as a result gas sensing devices that are highly sensitive and selective to such gases are in a high demand. Presently, gas sensors based on p-type NiO are pleasing more consideration, because of its excellent reproducibility, high specific surface areas, great sensitivity, low cost and environmental friendly. Herein, we reviewed the different synthesis methods on p-type NiO nanostructures and their application as gas sensors. The fundamental gas sensing mechanism related to the p-type NiO is briefly explained. The effects of noble metals, transition metals, and transition metal dichalcogenide and phosphors materials on the NiO gas sensing performance are also discussed in detail. Influence of 0D, 1D, 2D and 3D heterostructures on NiO gas sensing characteristics are also given. The arrangement of various semiconductor metal oxides to form heterostructures which further improve the selectivity and sensitivity of the sensing parameters is also discussed and we show that number of publications on heterostructures related to NiO increased drastically since the year 2010.