| As a kind of gas sensor, Zn O has a brilliant prospect due to direct band-gap and large exciton binding energy. In recent decades, 3D Zn O nanostructures have exhibited better gas sensing property than 1/2D Zn O nanostructures. So, by changing the experimental parameters, Zn O nanostructures with different dimensions have been successfully fabricated and controlled via an environment-friendly, low cost and power-consumption hydrothermal method. The effects of experimental parameters on the synthesis of the Zn O morphologies have been investigated, and the growth mechanisms of the Zn O nanomaterials have been simulated briefly. Moreover, the gas sensing property of the Zn O with different morphologies have been measured, and their gas sensing mechanisms have been analyzed respectively. The results and significance in the thesis are as follows.The Six kinds of Zn O morphologies with 1/2 dimensions have been successfully synthesized by an easy hydrothermal way. These Zn O morphologies are hexagonal nanorods, nanosheets, nanodiamonds, the sealed nanotubes, nanoparticles and nanorods. According to the experimental parameters and characterization, the Zn O nanodiamonds have been formed due to the negative C6H5O73- and the long reaction time. Besides, the constituent and structure of the growth units changed with adding the Na F and HMT. Then, the sealed Zn O nanotubes have been produced. When measured the gas sensing property, the Zn O hexagonal nanorods, nanosheets, nanodiamonds, the sealed nanotubes, nanoparticles and nanorods have the sensitivities of 4.8(100 ppm)、6.1(100 ppm)、7.5(100 ppm)、4.1(30 ppm)、2.212(10 ppm)' 4.131(10 ppm). Zn O nanodiamonds present the excellent gas sensing property among these morphologies, which have theoretically and practically significant effect on the synthesis of the sensors prepared with1/2D Zn O nanomaterials. Additionally, the radial Zn O nanoflowers, which have been assembled by 1D nanorods, have been fabricated after changing the experimental parameters. The flower-like Zn O nanostructures perform the sensitivity of 7.397 at the low concentration(10 ppm) of ethanol gas. 3D Zn O nanoflowers assembled with nanorods show better gas sensing property than the as-synthesized 1/2D Zn O nanostructure, which means that 3D Zn O nanomaterials have a more possibility to be applied in the industry.3D cake-like and flower-like Zn O nanostructures have been successfully prepared by the double surfactants assisted hydrothermal method. For Zn O nanocakes, sample Ⅲ, sampleⅡand sampleⅠhave the sensitivities of 10.9、9.1、8.5 to the 50 ppm of ethanol gas. For nanosheets assembled Zn O nanoflowers, the single-crystalline mesoporous nanosheets have been formed due to escaping of O2 reacted from H2O2 in the reaction solution, and the single-crystalline nanosheet overlaid each other to form the radial Zn O nanoflowers with large space driven by the HMT. Because of the existence of mesopore, nanosheet and space, the special surface area of Zn O nanoflowers come up to 36.866m2/g. Furthermore, the nanoflowers based sensor has a sensitivity of 35.2 to the 250 ppm of ethanol at the heating current of 160 ppm. So, the mesoporous nanosheets assembled Zn O nanoflowers have a potential application in sensor.The novel sunflower-like Zn O nanostructures, which comprise six triangle-like nanostructures and one sphere-like nanostructure, have been firstly synthesized. And, the average diameters of the triangle-like and sphere-like nanostructures are 500 nm and 800 nm, respectively. Based on the characterizations, the triangle-like nanostructure is single crystalline with the family of crystal face {001}, and mainly grows along six symmetric parallel planes, namely, ±(011-0), ±(101-0) and ±(11-00). Sunflower-like nanoflowers are self-assembled by one sphere-like and six triangle-like nanostructures due to the effect of C6H5O73- and the Zn-terminated +(0001). The sensitivity and response and recovery time of Zn O nanoflowers are 8,5s and 49.5, respectively at the 50 ppm NH3. Moreover, when the low concentration of NH3 is 10 ppm, the Zn O nanoflowers have the sensitivity of 25.7 and the response and recovery time of 11,5s,which suggests that the sunflower-like Zn O nanostructures reveal the superior NH3 sensing property, rapid NH3 response and recovery, high stability and large significance in industry. |
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