| With the development of the social economy,the use of natural resources by humans has become stronger,and the environmental problems have become more and more serious.Some toxic and poisonous gases are released to the atmosphere and cause acid rain,greenhouse effect,smog,etc.The warnings of harsh environmental phenomena remind people that it is important to protect the atmospheric environment.At the same time,in our daily lives,a number of safety issues such as gas emissions,food fermentation,acidification of drinks and so on can not be ignored.Therefore,the research and development of convenient sensor devices is very important,which is also a topic that must be crossed the development of science and technology today.Among various oxide semiconductors,SnO2,as an important n-type oxide semiconductor,has been widely used for gas sensor because of its good chemical and thermal stability,high sensing response,low cost,safe,and simple synthesis route.However,low selectivity,poor stability and high operating temperature are the main drawbacks of these conventional and simplex SnO2,which hinder their practical applications in monitoring toxic gases.Therefore,the optimization of SnO2 structure and composition is the extensively used strategies to achieve high gas sensing properties.Thus,in the present study,three kinds of SnO2 sensing material,namely,SnO2 microflowers,NiO-SnO2 microflowers and Co3O4-SnO2 microflowers were prepared by a one-step hydrothermal method.Their formaldehyde and trimethylamine(TMA)gas sensing properties were thoroughly investigated.According to a series of research,more useful information and understanding of SnO2 sensing material for a high performance gas sensor can be provided.The main research contents are as follows:1.SnO2 microflowers were synthesized by a one-step hydrothermal method.The gas sensing properties for formaldehyde were investigated.The results showed that SnO2 microflowers with diameter of 1-2 ?m are composed of many 10-20 nm nanosheets,which packed with each other.The optimal operating temperature was 200?,at which the sensitivity was 10.6.Moreover,it also showed rapid response and recovery times,good reproducibility and stability,and good selectivity,indicating potential application for fabricating high performance sensors.2.NiO-SnO2 heterojunction microflowers assembled with thin porous nanosheets were successfully synthesized through a facile one-step hydrothermal route.The results showed that NiO-SnO2 microflower sensor displayed the higher response at a lower operating temperature region compared to pure SnO2 microflower sensor.Meanwhile,introducing NiO obviously reduced operating temperature.Especially,the 5mol%NiO-SnO2 microflowers showed the higher responses,quick response-recovery characteristics and long-term cycling stability.The enhanced sensing properties were probably attributed to the formation of p-n heterojunctions at interface and the catalytic effect of NiO,which significantly enlarges surface depletion region and increases potential barrier.3.Co3O4-SnO2 heterojunction microflowers assembled with thin porous nanosheets were prepared via an one-step hydrothermal technique.The TMA gas sensing properties were studied.The results show that the sensor made of 5mol%Co3O4-SnO2 flower structure has a response of 9.3 to 5 ppm TMA at 175?,it was 2.9 times higher than pure SnO2 sensor and 7.2 times higher than pure Co3O4 sensor.The performance of the sensor may be attributed to the formation of p-n heterojunction and Co3O4 catalysis at the interface. |
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