UV-enhanced Gas Sensor Based On ZnSnO₃

It has been well known that SnO₂ and ZnO are wide band-gap semiconductors.As for composite mental oxide ZnSnO₃,it is a new type of gas-sensing material,showing excellent gas-sensing properties,thus getting more and more attention.But high operating temperature?above 200°C?is often a problem for the pristine ZnSnO₃-based gas sensor,which may result in poor stability,larger power consumption,and also limit the application in the explosive gas detection.Nano-TiO₂ having good UV photosensitive properties,in view of the above problems,this research introduced ZnSnO₃/TiO₂ composites to form ZnSnO₃-TiO₂heterojunctions,excited by UV light to cut down the operation temperature of the gas sensor.Firstly,the hollow cubic ZnSnO₃ was prepared by a facile co-precipitation method,and mixed with nano-TiO₂ particles.The thin film type sensor was fabricated by coating on the interdigital electrode.Experiments performed that the optimum operating temperature of the sensor was 80°C,and the gas-sensing properties was excellent at 80°C.Related mechanism studies suggest that the sensor based on ZnSnO₃/TiO₂ composite is obviously enhanced due to the synergistic effect of TiO₂loading and UV excitation:large amount of photon-generated electron-hole pairs were produced owing to UV excitation,and the heterojunctions formed on the surface of ZnSnO₃/TiO₂ composites resulted in efficient separation of photon-generated charges,and then accelerated the redox reaction at low temperature,thus enhancing the gas-sensing performance.In addition,the organic triethanolamine?TEOA?was added during the preparation of ZnSnO₃ hollow cube,and then flower-like ZnSnO₃ was successful prepared.Subsequently,5 wt%,10 wt%,20 wt%and 30 wt%nano-TiO2 particles were mixed with ZnSnO₃ to form different mass ratio of ZnSnO₃/TiO₂ composites,respectively,and the effect of doping amount on gas-sensing performance was investigated,the optimum mass ratio was obtained.Results are summarized that when the TiO₂ content is 20 wt%,the gas-sensing performance reaches best.Compared with hollow cubic ZnSnO₃,the working temperature of the gas sensor based on flower-like ZnSnO₃ is still 80°C.However,even at room temperature,the response to 1000 ppm ethanol also reached 36.6,and could detect ethanol concentrations as low as 10 ppm,which has the potential application value in room temperature detection.In summary,ZnSnO₃ with hollow cubic and flower-like morphology was prepared,and modified by TiO₂.The optimum operating temperature of ZnSnO₃/TiO₂composite film was 80°C under UV irradiation,and the other gas-sensing performance was excellent.It is worth noting that flower-like ZnSnO₃-based sensor has a high response to ethanol at room temperature.The method in this study provided a new idea to solve the similar problems of various gas sensors.