“…Because of the outstanding characteristics of easy manufacture, low power consumption, and cost, gas sensors are regarded as one of the effective approaches to the detection of toxic, harmful, flammable, and explosive gases. The basic working principle for oxide semiconductors gas sensors such as α-Fe 2 O 3 , 1,2 ZnO, 3,4 SnO 2 , 5−8 In 2 O 3 , 9,10 WO 3 11,12 (n-type) and Co 3 O 4 , 13,14 NiO 15,16 (p-type), et al, 17 is that the interactions between the surface adsorbed oxygen species and target gases lead to a remarkable change in the resistance. Therefore, the composition, crystalline size, surface morphology, and microstructure of oxide semiconductors play essential roles in determining the sensing properties.…”