Abstract
Two-dimensional (2D) nanomaterials, due to their unique physical and chemical properties, are showing great potential in catalysis and electronic/optoelectronic devices. Moreover, thanks to the high surface to volume ratio, 2D materials provide a large specific surface area for the adsorption of molecules, making them efficient in chemical sensing applications. ZnO, owing to its many advantages such as high sensitivity, stability, and low cost, has been one of the most investigated materials for gas sensing. Many ZnO nanostructures have been used to fabricate efficient gas sensors for the detection of various hazardous and toxic gases. This review summarizes most of the research articles focused on the investigation of 2D ZnO structures including nanosheets, nanowalls, nanoflakes, nanoplates, nanodisks, and hierarchically assembled nanostructures as a sensitive material for conductometric gas sensors. The synthesis of the materials and the sensing performances such as sensitivity, selectivity, response, and recovery times as well as the main influencing factors are summarized for each work. Moreover, the effect of mainly exposed crystal facets of the nanostructures on sensitivity towards different gases is also discussed.
Highlights
Owing to increasing widespread use in common applications such as industrial production, automotive, medicine, indoor air quality control, and environmental monitoring, gas-sensing technology is receiving more and more attention from both industry and academic research [1].The increased demand for highly sensitive, selective, cheap, low-power, reliable, stable, and portable sensors has stimulated extensive research to develop new sensing materials
Different types of metal oxide such as Zinc oxide (ZnO), SnO2, TiO2, In2 O3, WO3, TeO2, CuO, CdO, Fe2 O3, and MoO3 have been developed and employed in the fabrication of gas sensors and it was found that chemical components, surface state, morphology, and microstructure play important roles in gas-sensing performance [5]
5b) was reported, much of higher smooth porous authors attributed the superior performance of the 3D hierarchical porous ZnO to its highly open, porous structure and the high the high specific surface area conferred by the interconnected gas-sensing performance of the
Summary
Owing to increasing widespread use in common applications such as industrial production, automotive, medicine, indoor air quality control, and environmental monitoring, gas-sensing technology is receiving more and more attention from both industry and academic research [1]. Due to the high surface to volume ratio, 2D materials provide a large specific surface area and numerous active sites for gas adsorption, which, along with the fast charge transfer ability and tunable chemical and physical properties with the thickness, make these materials efficient in chemical sensing applications. Zinc oxide (ZnO), an n-type semiconductor with a wide bandgap of 3.37 eV, because of its unique optical and electronic properties, in addition to attracting considerable attention in potential applications such as solar cells, optoelectronic devices, nanogenerators, and catalysts [11], has been one of the most investigated sensitive materials for gas sensors [12]. The synthesis of the material and the sensing performance such as sensitivity, selectivity, response, and recovery times as well as the effect of different exposed facets of ZnO are discussed
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