| With the development of science and technology,environmental pollutions are becoming increasingly serious.Volatile organic compounds(VOCs),which are widely used in industrial production and daily life,are closely related to our life and will cause serious harm to animals and plants.Therefore,it is of great significance to accurately and effectively monitorand detect VOCs in the living environment for protecting the environment and building a safe living environment.Gas sensor is one of the convenient and effective detection methods,and the development of highly sensitive and selective sensing materials is very important.Among them,the metal oxide semiconductor such as tin dioxide has the advantages of wider band-gap,higher stability and low preparation cost,and it has application potential in the detection of VOCs.However,the pure tin dioxide-based sensors still have many problems,such as low sensitivity,low selectivity,and high operating temperature.Therefore,It is important to improve the performance of a single sensor material by the strategy of constructing heterojunction.The aim of this thesis is to improve tin dioxide's gas sensitivity to triethylamine.A series of composite materials such as the heterojunction of tin dioxide with copper oxide,graphite carbon nitride and reduction of graphene oxide have been constructed by hydrothermal methods.Moreover,adjustable synthesis of controlling morphology and the influence of the morphology and structure of tin dioxide-based materials on the gas-sensitivity of triethylamine have been studied.The main research contents and conclusions are as follows:(1)The 3D layered Cu O/Sn O2 composites were synthesized by hydrothermal method,and the Cu O/Sn O2 heterojunction was controlled by changing the contentof copper precursor.Both 3D laminated Sn O2 and Cu O/Sn O2 materials have good sensing performance for triethylamine.Among them,the Cu O/Sn O2-3 composite material has a response value of 163to 100 ppm triethylamine at 340°C,and for 1 and 5 ppm the response value of low-concentration triethylamine is 3 times and 5 times that of pure Sn O2,and has higher selectivity and stability.The results indicate that the sensing performance of tin dioxide for the detection of low concentration triethylamine can be effectively improved by adjusting the heterojunction of the composites.(2)SnO2 and g-C3N4/Sn O2 composites were synthesized by the method of first hydrothermal and then calcined.By changing the ratio of g-C3N4 and raw materials,the control of the heterojunction of g-C3N4/Sn O2 was realized,and the influence of different g-C3N4/Sn O2 heterojunction materials on the gas sensitivity of triethylamine was explored.The research results show that the n-n heterojunction composite(g-C3N4/Sn O2-5)formed at the interface of g-C3N4 and Sn O2 has a response of 23 to 100 ppm triethylamine at 240°C,which is higher than the sensitivity of pure tin dioxide material and has good stability.The gas-sensitive mechanism of g-C3N4/Sn O2 composite for detection of triethylamine is also analyzed.(3)The rGO modified 3D layered Sn O2 heterojunction materials were prepared by hydrothermal method with the assistance of phthalic acid.The r GO/Sn O2 heterojunction was regulated by changing the doping amount of r GO,and the gas sensing mechanism was analyzed.The results show that in the r GO/Sn O2 material with large specific surface area,there is a heterojunction at the interface between Sn O2 and r GO,and the material shows excellent gas sensitive property of triethylamine.Compared with the operating of pure Sn O2(240°C),the doping of Sn O2 with r GO significantly reduces the operating temperature of Sn O2 composites.At 180°C,the detection limit of the r GO/Sn O2-0.2 for triethylamine reached 358 ppb,with high selecticity.The lower operating temperature is beneficial to reduce energy consumption of the sensor,prolong the service life and improve the stability. |
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