Preparation Of ZnO Nanorod Arrays And Their Gas Sensing Properties

With the rapid development of human society,the environmental problems caused by harmful gases are becoming increasingly serious.Using high-performance gas sensors to monitor harmful gases quickly and efficiently is the premise to solve this kind of environmental pollution.Among many semiconductor metal oxides,ZnO has attracted wide attention because of its mature and simple preparation process,high electron mobility and good physical and chemical properties.However,the commercial ZnO gas sensor has some shortcomings such as high working temperature,low sensitivity and poor selectivity.It is an effective way to improve the sensitivity and selectivity of ZnO gas sensor by improving morphology,doping modification and forming P-N junction.Therefore,ZnO nanorod arrays(hereinafter referred to as ZnO NRs)were directly grown on the alumina ceramic tube substrate by hydrothermal method,and then modified by Co ion doping.the composition and morphology of the samples were characterized by means of x-ray diffraction(XRD)and scanning electron microscope(SEM).The response of the sample to different gases was evaluated by changing the working temperature,the types and concentrations of gases,and the change rules of gas sensitivity of ZnO NRs was explored.With zinc nitrate,hexamethylenetetramine,polyethyleneimine and ammonia as raw materials,ZnO NRs was grown on alumina ceramic tube substrate by hydrothermal method,and the influence of seed solution with different impregnation times on the morphology of ZnO NRs was studied.The results show that when the impregnation times are 10 times,the density distribution of ZnO NRs is uniform and the gap between nanorods is moderate.At the working temperature of 200?,The response values of ZnO NRs to H2S at 100 ppm is up to 19.547.In 9 kinds of gases(ethanol,formaldehyde,ethylacetate,toluene,xylene,acetone,H2S,NH3 and CO)at 100 ppm,ZnO NRs samples show excellent selectivity and stability to H2S.Co-doped ZnO NRs was prepared by one-step hydrothermal method by introducing cobalt nitrate into the growth solution on the basis of ZnO NRs.The results show that when the concentration of cobalt nitrate is 0.004 M,the morphology distribution of nanorods is uniform and the gap is moderate.Under the conditions of 100 ppm H2S and 200?,the response value at 0.004 M reached 32.982.Co doping did not change the working temperature and H2S selectivity of ZnO NRs,and the response value increased by 68.73%,showing excellent stability.