Study On The Gas Sensing Properties Of Light Activated Ag/ZnO Nanostructure Sensor

Recently,ZnO has been widely used for various gas sensors due to its morphology easy control,easy fabrication and low-cost.ZnO-based sensors have some advantages such as high sensitivity,fast response,and good stability,while working temperature generally is high at range from 300 °C to 400 °C.The high working temperature not only lead to high power consumption,but also is easy to cause explosion in the detection of flammable and explosive gases,which exists potential safety hazard and is disadvantage to the practical application.Based on this information,ZnO nanostructure with different morphologies have been successfully synthesized on Al2O3 ceramic wafer with Ag electrode by one-step aqueous solution method.On the basis of loading Ag nanoparticles on the ZnO nanostructures surface,the means of UV-light irradiation was used to reduce the working temperature of the ZnO nanostructure further,and improve its gas sensing properties.Firstly,By one-step aqueous solution method,ZnO nanosheets network structure was grown on Al2O3 ceramic wafer with Ag electrode in zinc acetate growth solution with 0.02 mmol,0.05 mmol,0.1 mmol and 0.2 mmol citric acid sodium,respectiveily.The thickness of the prepared nanosheet was between 10 nm and 20 nm.After annealing at 400 °C for 30 min,ZnO porous network structure composed of nanoparticleswas obtained.The sample gorwn in growth solution with 0.1 mmol C6H5Na3O7·2H2O showed the highest response to ethanol at the optimum operating temperature of 350 °C among four samples.By one-step aqueous solution method,the various ZnO nanorod arrays were grown on Al2O3 ceramic wafer with Ag electrode in 10 mmol/L,25 mmol/L and 50 mmol/L zinc nitrate growth solution,respectively.The average diameter of the ZnO nanorods were about 60 nm and the rods length were about 300 nm.The density of ZnO nanorods gradually increases with the concentration of the growth solution,and the response of ZnO nanorods sensor to ethanol increases at the optimum operating temperature of 350 °C as well.Secondly,Ag nanoparticles were loaded on the ZnO porous network structure sensor prepared in zinc acetate solution with 0.1 mmol C6H5Na3O7·2H2O and the ZnO nanorods sensor prepared grown in 25 mmol/L zinc nitrate by photoreduction method.The optimum operating temperature of Ag/ZnO porous network structure and Ag/Zn O nanorod arrays sensor are about 250 °C and 300 °C,respectively.The results show that the load of Ag nanoparticles decrease the operating temperature of the ZnO sensors,but resulting in increase of the sensor recovery time.Finally,the sensing performance of ZnO and Ag/ZnO sensor were investigated under 395 nm and 365 nm UV irradiation.The sensors show obvious response to 50 ppm ethanol at 50 °C.The results showed that the working temperature of sensors can significantly reduced under optical activated.