Preparation And Gas-sensing Properties Of Graphene Doped Zinc Oxide And Tin Dioxide Nanocomposites

Metal oxide semiconductors are the important materials in gas-sensingfields. However the applications of metal oxides as sensing materials indetecting volatile toxic substances are limited due to the high workingtemperature and low selectivity. The reported results show that metaloxide-based gas sensors are used widely to detect COx, H2and NOx. Theinvestigations focused on the detection volatile organic compounds with lowconcentration at low temperature are still significant. Therefore, it is necessaryto synthesize novel gas-sensing materials used for detecting toxic volatilecompounds effectively.To improve the gas-sensing properties of metal oxide semiconductor,nanosize zinc oxide with different morphologies and graphene doped zinc oxideand tin dioxide nanocomposites were synthesized. The effects of themorphology, structure and the doping amount of graphene of the materials onthe gas sensing properties were studied and some valuble datas for detectingvolatile gases were gotten. Main contents and conclusions are as follows:(1) Zinc oxide with controlled morphology was synthesized by hydrothermal method. The gas sensing properties of the as-prepared zinc oxideto various volatile organic compounds were investigated. The results show thatthe morphology of zinc oxide has great impact on its gas-sensing properties.The prism-like zinc oxide with large ratio of length to diameter exhibits goodsensitivity and high selectivity to triethylamine at100oC, while the lamella-likezinc oxide shows good response to acetaldehyde.(2) The zinc oxide nanorods doped with graphene nanocomposites weresynthesized. The influences of graphene quantity on the gas sensing propertieswere studied. The results show that the amount of graphene has obviousinfluence on the sensitivity of the nanocomposites. The as-prepared zincoxide/graphene sensors exhibit much better gas sensing behavior in sensitivityand selectivity to volatile organic glycol gas as compared with pure zinc oxide,the sensors based on composites show the optimal gas sensing properties towardglycol when the doping amount of graphene was1.2wt.%, which shows that thezinc oxide nanorods decorated with graphene can effectively apply to detect lowconcentration glycol at low working temperature.(3) The graphene doped zinc oxide nanocomposites were prepared byhydrothermal method. The structure, morphology and gas sensing properties ofthe composites were studied. The mechanism of the influence of graphenequantity on gas sensing properties was also elaborated. The results show that thegas sensing response of the composites toward ethanolamine increased greatlyas compared with pure zinc oxide. The as-prepared graphene doped zinc oxide nanocomposites possess excellent sensing properties when the doping amountof graphene reached0.25wt.%.(4) Graphene doped tin dioxide nanocomposites were synthesized viahydrothermal method. The gas sensing properties were also tested. The resultsshow the graphene can enhance the gas-sensing properties of tin dioxide. Thenanocomposites have better gas sensitivities than pure tin dioxide. Particularly,tin dioxide/graphene nanocomposite containing0.6wt.%graphene exhibits theoptimal gas-sensing performance towards formaldehyde at the optimaloperating temperature of120oC.