The Study Of Gas-sensitive Properties Of ZnO And ZnO/Graphene Composites

Gas sensor is a sensor that can convert the composition and concentration ofmaterials into corresponding electrical signals. Zinc oxide (ZnO) with a large band gapand a large activation energy is widely used in gas sensor field. Studies have shown thatZnO is responsive to a variety of gases. Because of the special electronic structure, ZnOhas been widely used in the field of gas sensitive materials. In this paper, ZnO nanorodsarray was prepared by hydrothermal method and spread on a flat plate electrode. SEManalysis showed that the growth direction of dense ZnO nanorods array was perpendicularto the substrate and the diameter of ZnO nanorods was between30nm to50nm. X-rayanalysis showed that the ZnO nano-arrays which grew along with the c-axis werehexagonal wurtzite structure. In this experiment, we presented the gas sensitivecharacterization of ZnO nano-arrays for detecting methanol, ethanol, acetone, nitrogendioxide under a practical environment. By the contrast analysis, the optimum operatingvoltage of ZnO nano-arrays for detecting the four gases was5.37V,4.73V,4.73V,4.00V,respectively. The response mechanism of gas sensing in different gas atmosphere wasinvestigated.The composite materials were prepared by co-precipitation, in which the ratio of Zincnitrate to graphene oxide was9:1,8:2,7:3,6:4, respectively. SEM analysis showed thatthe ZnO arrays were distributed between graphene sheets. X-ray analysis and Ramanspectra tests showed that there were no other characteristic peaks but the peaks of ZnOand graphene in the conposites. The gas sensitive characterization of the compositematerials for detecting different concentrations of nitrogen dioxide at differnet temperaturewas investigated. By the contrast analysis, when the ratio was9:1, the gas sensitivecharacterization and practicality was the excellent. The gas sensitive responsivenessmechanism of the composites for detecting nitrogen dioxide was explained. Researchesshowed that the composites was only responsive to nitrogen dioxide. The gas sensitiveselectivity of the composites for detecting nitrogen dioxide increased compared with pureZnO. In term of sensitivity, the composites possessed higher sensitivity than pure graphene.