“…In recent years, gas sensors based on metal oxide semiconductors are considered a convenient and simple analysis technique for conventional VOCs. Metal oxide semiconductors, such as WO 3 , , ZnO, α-Fe 2 O 3 , NiO, CO 3 O 4 , In 2 O 3 , and SnO 2 , have been extensively explored as gas-sensing materials because of their excellent sensitivity, rapid response–recovery time, and concise preparation process. Recently, some researchers confirm that the sensing properties of metal oxides are decided by the morphology, nanostructure, and composition of sensing materials. − Thus, many investigations on surface structure and dimension are conducted to increase gas-sensing performance as much as possible by regulating the surface active site and adsorption process.…”