Semiconductor Oxides Prepared Via Microwave Hydrothermal Method And Its Sensing Properties

Metal oxide semiconductors (MOSs) are widely used as gas sensing materials, which possess the advantages of chemical and thermal stability, compatibility with modern electronic devices, simplicity, high sensitivity and low cost. In this thesis, we report a facile and rapid microwave-assisted hydrothermal method to obtain MOSs with different morphologies and structures. The properties of gas sensors based on samples were characterized through the static volumetric method towards various gases. The results are listed in the followings:1:The precursor In(OH)3 was firstly synthesized by microwave-assisted hydrothermal method by using Inl3·4H2O as raw material. Then the precursor was calcined to obtain In2O3 nanorod. At the same time, the quantity of urea was adjusted to explore the growth process of In2O3 nanorods. The experimental results show that the In2O3 sensor exhibites high sensitivity, rapid response and recovery, low working temperature and low detection limit towards NO2.2:SnO2 and Au/SnO2 nanorods were synthesized by microwave-assisted hydrothermal method with SnCl2·2H2O and AuCl3HCl·4H2O as raw materials. These nanorods were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the Au/SnO2 sensor exhibited higher sensitivity, wider detection range, better selectivity, faster response and recovery characteristics to ethanol in contrast to pure SnO2 sensor at 120?. These results predict that Au/SnO2 gas sensor has good prospective applications in low concentration ethanol detection.3:ZnO and Au/ZnO hollow spheres were synthesized by microwave-assisted hydrothermal method with Zn(Ac)2?2H2O as raw materials, C6H5Na3O7·2H2O CO(NH2)2 and AuCl3·HCl·4H2O were used as the nodulizer, porogen and dopant, respectively. The structures and morphologies of these hollow spheres are well characterized here. The gas sensing results show that the gas sensor based on ZnO hollow spheres showed high sensitivity, low detection limit, excellent selectivity and low working temperature to ethanol. After loading with Au, the Au/ZnO sensor shows even higher sensitivity, faster response and recovery and lower operating temperature comparing to isolated ZnO sensor.