| In people’s production and livelihood, it is difficult to avoid using or emitting some gases with toxicity and flammability, such as nitric oxide, sulfur dioxide, hydrogen, carbon monoxide,methane,formaldehyde, acetone and so on. Once those gases leak out into into air, it will lead a serious threat to people’s health and life.. So, it is necessary for us to use a gas sensor to monitor the changes in atmosphere at our living and working place.The gas sensor based on oxide semiconductor has been attracting people‘s attention due to the advantages of high sensitivity, fast response, good portability and low price. The gas sensing performance of a gas sensor is usually decided by sensitivity of the used sensing material. In this paper, we intent to improve the properties of gas sensor based on semiconductor though modifying the sensing material. Here, we use some synthetic technologies to prepare Zn O nanomaterial with different morphologies, electrospunning nanofibers of p-type Ni O/n-type Zn O heterojunction and oxide semiconductor nanomaterials decorated with noble metal. Main contents include:(1) We found a new hydrothermal process to control the morphology of Zn O and prepare Zn O nanorings assisted by polyving akohol 1788(PVA-1788). And the influences caused by PVA-1788 and hot water bath pre-treatment on the morphology of Zn O were investigated. Then the trimethylamine(TMA) sensing properties were investigated. Compared with Zn O nanoplates, the Zn O nanorings markedly improved their trimethylamine(TMA) sensing properties including higher response, lower detecting limit, and better selectivity.(2) We prepared Zn O nanofibers with a diameter less than 100 nm by electrospunning method, and investigating their trimethylamine(TMA) sensing properties. The result revealed Zn O nanofibers showed an excellent TMA sensing properties, including high response(100 to 100 ppm TMA), low detecting limit(5 ppm), fast response and recovery time(less than 5 s and 13 s, respecctively) and good selectivity. In order to further improve the TMA detection capability, electrospunning nanofibers of p-type Ni O/n-type Zn O heterojunction with different content of Ni O were prepared to fabricate TMA sensors. And the effects of Ni O content on their TMA sensing properties were investigated. The results showed when the Ni O content was 4 mol%, Ni O/Zn O nanofibers showed highly enhanced TMA sensing properties, including 8 times higher response to 100 ppm TMA than that of Zn O nanofibers, the lower detecting limit down to 0.5 ppm, and excellent selectivity.(3) We fabricated the acetylene sensor based on Zn O nanorings decorated with Au nanoparticles(Au-Zn O nanorings). We successfully decorated Au nanopaticles with a size of 3 nm to 10 nm on the surface of Zn O naorings, and the sensor based on Au-Zn O nanorings, compared with the one based on Zn O nanorings, showed the enhanced acetylene sensing properties, including: a) decreasing the optimal operating temperature from 302 °C down to 255 °C, which was far lower than the ignition temperature of acetylene(305 °C) and made the sensor work more safely; b) decreasing the detectable limit to below 1 ppm; c) fast response and recovery time(less than 13 s and 5 s, respectively).(4) Due to plenty of unsaturated bonds, the facets with high surface energy usually have a high catalytic activity and strong adsoption, which is benefit for the enhancement of gas sensing properties of materials. Noble metal with a nanoscale size usually shows an excellent catalytic activity. Here, we combined the advantages of the both by preparing nanoscale Au nanoparticle-decorated Sn O2 nanocrystallines with exposed high energy facets. And the Au nanoparticle-decorated Sn O2 nanocrystallines showed highly enhanced sensing properties against acetylene and carbon monoxide.
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