Synthesis And Modification Of ZnO Microstructures For Enhanced Gas Sensing Performance And Photocatalysis Properties

Zn O, a wide bandgap and high exciton binding energy of semiconductor material, because of its low cost, good light sensitivity, strong oxidizing, non-toxic, and excellent chemical stability and other characteristics are widely used in the field of gas sensing and photocatalysis. Therefore, the study of preparation, modified, gas sensing and photocatalysis of ZnO material has caused extensive research interest.In this dissertation, ZnO nanowires are prepared by hydrothermal method, and the gas sensing properties to VOCs are investigated. At the same time, the change of flower-like Zn O microstructures’ morpholory and crystal structure after the doping of Mn are studied, and the gas sensing properties and photocatalytic properties are also investigated. The main conclusions could be obtained as follows:(1) ZnO nanowires are fabricated by hydrothermal method, and the gas sensing properties of ZnO nanowires are investigated for volatile organic compounds(VOCs). The gas sensing sensitivity of ethanol and acetone can reach to 4.58 and 2.63 under 500 ppb at optimal working temperature(200℃), and the detection limit can be lower to 50 ppb.(2) Pristine and Mn-doped(0.25 mol%. 0.5 mol%, 1.0 mol% and 3.0 mol% Mn) flower-like Zn O microstructures synthesized via a simple one-step solution route at room temperature are characterized, and the results showed that flower-like microspheres were smaller and smaller, and the structure became more and more loosely. Moreover, Mn3O4 nanoparticles are decorated on the surface of ZnO microstructures.(3) The gas sensing properties to 100 ppm acetone, ethanol and toluene of gas sensors based on pristine and Mn-doped flower-like Zn O microstructures are investigated. The results indicated that all the gas sensors hold the optimal working temperature of 200 ℃,and the gas sensing properties of pristine flower-like Zn O microstructures are effectively improved by Mn doping. The sensitivity of the 0.5mol% Mn-doped flower-like Zn O microstructures reached a maximum, and the gas sensitivity to acetone is higher than ethanol and toluene.(4) The photocatalytic performances of Mn-doped flower-like ZnO microstructures with various doping concentration were studied using methyl orange as the stimulant pollutant and UV lamp as light source. The measured results indicated that Mn-doped Zn O microstructures can improve the performance of photocatalytic degradation.