The Preparation Of ZnO Nanostructures And Their Application In Gas Sensors

ZnO,as a wide bandgap oxide semiconductor,is widely used in the fields of photocatalysis,gas sensing,surface acoustic wave device and so on because of its unique optical,electrical and piezoelectric properties.In recent years,ZnO has attracted much attention in the gas sensing applications.The gas sensing response of ZnO is primarily controlled by its surface resistance.Therefore,the nano-structure ZnO with large specific surface area is benefit to improve its gas sensing property.In addition,considering the extremely high carrier mobility and special transport property of carbon nanotubes and graphene,their composite materials with ZnO can also exhibit excellent gas sensing properties.The main contents of this paper are as follows:ZnO nanorods?ZnONRs?were grown directly on the generally used sensing electrodes of alumina ceramic tubes by a hydrothermal method.Carbon nanotubes?CNTs?were assembled on the surface of the ZnONRs using ultrasonic dispersing.The ethanol gas sensing properties of the prepared ZnONRs gas sensor and the ZnONRs/CNTs nanocomposite gas sensor were investigated.The optimal working temperature of two gas sensor are 370?,At optimal working temperature of 370?,the response to 100ppm ethanol is 26.1 for the ZnONRs/CNTs nanocomposite gas sensor,A short response time of 2s and a recovery time of 16s are achieved for the ZnONRs/CNTs nanocomposite gas sensor.Moreover,the long-term stability and repeatability of the ZnONRs/CNTs nanocomposite gas sensor were also discussed.The improved ethanol sensing properties of the ZnONRs/CNTs nanocomposite gas sensor can be attributed to the synergistic effects of the ZnONRs and CNTs,including the large specific surface area,high electron transport capability and the heterojunctions between p-type CNTs and n-type ZnONRs.Graphene were grown directly on the generally used sensing electrodes of alumina ceramic tubes by CVD method.ZnONRs were synthesized onto the ceramic tubes coated with graphene to form graphene/ZnONRs nanocomposites.The ethanol gas sensing properties of the prepared ZnONRs gas sensor and the graphene/ZnONRs nanocomposite gas sensor were investigated.The optimal working temperature of graphene/ZnONRs nanocomposite gas sensor is 370?.At optimal working temperature of 370?,the response to 100ppm ethanol is66.2 for the graphene/ZnONRs nanocomposite gas sensor,A short response time of 1s and a recovery time of 5s are achieved for the graphene/ZnONRs nanocomposite gas sensor.Moreover,the long-term stability and repeatability of the graphene/ZnONRs nanocomposite gas sensor were also discussed.The improved ethanol sensing properties of the graphene/ZnONRs nanocomposite gas sensor can be attributed to the synergistic effects of graphene and ZnONRs,including large specific surface area,rich functional groups and high electron transport capability.ZnO nanosheets?ZnONSs?were synthesized directly onto Al₂O₃ ceramic tubes by introducing an Al nano-interlayer.The preparation and the ethanol gas sensing properties of the ZnONSs gas sensor were investigated.The optimal working temperature of Al-doped ZnO ultrathin nanosheets gas sensor is 370?.At optimal working temperature of 370?,the response to 100ppm ethanol is 90.2 for the ZnONSs sensor.A short response time of 1.6s and a recovery time of 1.8s are achieved for the ZnONSs sensor.Moreover,the long-term stability and repeatability of the ZnONSs sensor were also discussed.The excellent sensing properties of the ZnONSs are attributed to large specific surface area,the doping of Al,abundant intrinsic defects and high surface energy of the exposed planes.