Preparation, Characterization Of Zinc Oxide Nanomaterials And Gas Sensing Properties

Gas sensors based on zinc oxide (ZnO), which have simple structuret, arenow widely used for detection of toxic and flammable gases. But those gassensors have some disadvantages such as poor sensitivity and poor repeatabilitywhich limit their wide applications in gas sensors. In this thesis, the morphologyof microrod flower-like ZnO and nanosheet flower-like ZnO were controlled bystudying the experiment parameters deeply and the gas sensing properties wereimproved very well.Flower-like ZnO made of microrod was synthesized through a simple andlow temperature (90°C) hydrothermal method. Polyethylene glycol (PEG) wasused to generate active sites which allowed the growth of microrod flower-likeZnO. The diameter of rod is about250~350nm with hexagon in one end and thediameter of flower is about5μm.Flower-like ZnO made of nanosheets was synthesized through changing theconcentration of NaOH and adding PEG or not. The thickness of nanosheet isabout10nm and the diameter of flower is about2μm. The result showed thatzinc nitrate was better than zinc acetate by changing the source of Zn2+.The morphology, structure, composition and defect were analyzed by SEM(Scanning Electron Microscope), XRD (X-ray Diffraction), Raman (RamanSpectroscopy), FTIR (Fourier Transform Infrared Spectroscopy) and PL(Photoluminescence). The samples synthesized in this thesis are wurzitehexagonal structure ZnO with lots of surface defects.Gas sensing properties of microrod flower-like ZnO and nanosheetflower-like ZnO were tested which showed that the optimum working temperatueof acetone, ethanol, acetone and ammonic are200°C,250°C,350°C,350°Crespectively. The response of microrod flower-like ZnO to acetone at0.1ppm,1ppm,10ppm,20ppm,50ppm and100ppm are3.58、5.93、12.74、15.43、20.53、24.35which are4%、37%、53%、43%、34%and35%higher than nanosheetflower-like ZnO. The response time and recovery time of microrod flower-likeZnO to acetone at0.1ppm,1ppm,10ppm,20ppm,50ppm and100ppm are15~29s and10~18s. The response time and recovery time of nanosheet flower-like ZnO to acetone at0.1ppm,1ppm,10ppm,20ppm,50ppm and100ppm are13~28s and10~17s, which are better than microrod flower-like ZnO.The response of microrod flower-like ZnO and nanosheet flowr-like ZnO wastested after120days, which shows good stabitlity. Flower-like ZnOnanostructure prepared with the method of this thesis has good sensitivity, andshows good application prospect for the gas sensor.