| Due to the gas sensor can detect, monitor and give an alarm for measured gases, they have very important application in environmental monitoring and protection, food safety, household gas, industrial and mining enterprises of production safety and other fields. Semiconductor resistance type gas sensor became one of the most widely used in different kinds of sensors due to its high sensitivity, fast response speed, good stability, and small volume, easy to carry. As a kind of wide bandgap semiconductor metal oxide, zinc oxide is one of the most common types of gas sensitive materials, it has gas sensing properties to many kinds of gas. But pure zinc oxide gas sensor has a disadvantage of higher working temperature and poor selectivity, which limit its wide application. In recent years, the studies have shown that graphene-like structure of molybdenum disulfide has good electrical conductivity and large specific surface area and high reactivity. Therefore combine the ZnO and MoS2 will helpful to improve its gas sensitive properties. The main research work of this paper is as follows:1. In this paper, 3D hierarchical MoS2 nanostructures were successfully synthesized through hydrothermal method. Its gas sensing property is bad after the performance testing. But surface modification with noble metals is considered as an effective strategy to enhance gas sensing performance. Thus a novel gas sensing material was prepared by decorating Au nanoparticles on MoS2 hierarchical nanostructures. The morphology and microstructure were characterized by X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), energy dispersive spectroscopy(EDS) and transmission electron microscopy(TEM). The results clearly reveal that Au nanoparticles with sizes of 10-20 nm were deposited on the surface of MoS2 nanosheets uniformly. Furthermore, the MoS2 hierarchical nanostructures are further employed as a support to load Au nanoparticles to construct nanocomposites for chemical gas sensors. Experimental results indicated that the Au nanoparticles-functionalized MoS2 hierarchical nanostructures gas sensor has some response to NH3 at low temperature.2. The ZnO nanoparticles-coated MoS2 nanosheets were successfully fabricated by two step hydrothermal method. Results show that the ZnO-coated MoS2 nanosheets are about 500 nm in diameter. The scale of ZnO nanoparticles are about 8 nm. Furthermore, owing to the supporting substrate of specific two-dimensional MoS2 nanosheets, the sensor based on ZnO nanoparticles-coated MoS2 nanosheets exhibit superior gas sensing performance towards ethanol and it maybe have potential applications in the detection of ethanol vapors. SnO2 nanoparticles dispersing on the surfaces of MoS2 nanosheets were also prepared by two step hydrothermal method to explore gas sensitive performance. And the sensor based on SnO2@MoS2 composites also exhibits high response and good selectivity to ethanol gas.3. Hierarchical nanostructures MoO3 are very promising gas sensing materials due to their well-aligned structures with less agglomerated configurations. In this paper, hierarchical MoO3 nanostructures were successfully synthesized through the oxidization conversion of hydrothermally synthesized MoS2 precursors. The results clearly reveal that MoS2 precursors can completely transfer into MoO3 via the annealing process at 400 oC. And the as-prepared hierarchical MoO3 nanostructures are about 500 nm in diameter, which are constructed by relatively densely packed nanosheets with the thickness of around 5-10 nm. Furthermore, owing to the well-defined and uniform hierarchical structure, the sensor based on hierarchical MoO3 nanostructures shows superior gas sensing performance towards ethanol and it maybe has potential application in the detection of ethanol vapors. To improve gas sensitive performance, we used a simple way to fabricate molybdenum oxide nanocomposites by surface modification with Au nanoparticles. Through the structure characterization and performance testing, we knew that the MoO3 hexagonal sheets are about 600 nm in diameter, and the scale of Au nanoparticles are around 10-15 nm. Furthermore, the sensor based on Au distribute to MoO3 hexagonal sheets showed superior gas sensing performance towards ethanol and it maybe have potential applications in the detection of ethanol vapors. |
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