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ZnO and Zn1-xMnxO Minicrystal by CVT and Temporal Process of Photoelectrons
The ZnO and Zn1-xMnxO minicrystal were synthesized by chemical vapor transport (CVT). The electron trap structure (donor level) and process on the temporal behavior of photoelectrons of materials were respectively studied by thermo-luminescence and microwave absorption dielectric spectrometry. There are two peaks in the thermo-luminescence spectra in pure ZnO, one is -183 ℃ and the other is -127 ℃, which shows two kinds of electron trap energy level produced by the intrinsic defects in ZnO;but obtain very low thermo-luminescence that only equals to ten percent of pure ZnO in Zn1-xMnxO, which shows that its intensity of electron trap is less. The studies of microwave absorption dielectric spectrometry show that conduction band photoelectrons are two-step exponential decay process in ZnO, the lifetime of rapid process is 83 ns, while slow process is 828 ns, the reason of delay is relaxation effects of electron trap to conduction band photoelectrons. The intensity of electron trap is less in Zn1-xMnxO minicrystal, the relaxation effects of conduction band photoelectrons from electron trap is little, so electrons disappeared quickly at conduction band, and the decay process of photoelectrons is only 10～20 ns....
2020-11-11 22:33:38浏览：74
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Preparation and Ethanol Sensing Properties of ZnO Nanofibers
ZnO nanofibers with an average diameter of about 90 nm were prepared by an electrospinning method combined with a calcination process.The as-electrospun nanofibers before and after calcination were characterized by means of differential thermal analysis(DTA),thermal gravimetric analysis(TGA),X-ray diffraction(XRD) and scanning electron microscopy(SEM).The fibers after calcination at 600 ℃ belong to the hexagonal wurtzite structure.The sensor based on ZnO nanofibers exhibited excellent ethanol sensing properties at 206 ℃ such as good linear dependence in the low concentration(1-100 μL/L),high response,and good selectivity.Fast response(less than 2 s)and recovery(about 16 s) were also observed in our investigations....
2020-10-22 17:35:41浏览：80
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Filter paper-templated preparation of ZnO thin films and examination of their gas-sensing properties
ZnO thin films prepared by using quantitative filter paper as a template and Zn(CHsCO2)2·2H2O ethanol precursor solution were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of sample calcination temperature, precursor concentration and filter paper types were studied, and the growth process was investigated by infra-red (IR) spectroscopy and thermogravimettic analysis/differential thermal analysis (TGA/DTA). The results show that samples soaked in a 1.5 mol/L Zn( CH3 CO2 )2.2 H2O ethanol solution and calcined at 600 ℃ yield ZnO films of uniform particle size, approximately 30, 40 and 50 nm, for fast-, medium- and slow-speed filter papers, respectively. The formaldehyde gas sensing properties of the ZnO nanoparticles were tested, showing that the material prepared from fast-speed filter paper has a higher response to 120-205 ppm formaldehyde at 400 ℃ than that prepared from medium- or slow-speed paper, which depends on the particle size....
2020-09-15 12:28:59浏览：75
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Fabrication and gas sensing property of honeycomb-like ZnO
We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerationsfabricated by direct precipitation method. X-ray diffraction (XRD), energy-disperse X-ray spectrometry (EDS), scanning electronmicroscopy (SEM) showed that the as-prepared ZnO calcined at 700℃ were micron sphere particles with honeycomb-likestructure. In the UV-vis absorbing spectrum, it was observed that there is a new additional absorption band at 260 nm, and it wasspeculated that the absorption may be caused by defects on the surface and interface of honeycomb-like ZnO. The as-productsshowed high sensitivity and short response time to sulfured hydrogen gas. These results demonstrate that honeycomb-like ZnOconglomerations are very promising materials for fabricating H2S gas sensors.2008 Chao Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved....
2020-09-15 12:28:59浏览：65
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