Preparation And Gas Sensing Properties Of Inverse Opal Structural SnO₂ And WO₃

With the acceleration of industrialization,air pollution has become a serious environmental problem in today's society.The research and development of high-performance gas sensors for timely and accurate detection,analysis and early warning of hazardous gases in the environment is of great significance to the national economy and production and life.At present,the semiconductor resistive gas sensor based on metal oxide is one of the most widely studied and applied.In this thesis,in order to effectively improve the response performance of metal oxide gas sensor,WO3 and SnO2 gas sensing materials with inverse opal?IO for short?structure were designed and constructed.The purpose of this paper is to use their three-dimensional ordered porous structure to enhance the diffusion and contact reaction efficiency of gas molecules in gas sensing materials,and then improve the sensitivity and response recovery of the sensor.Through the design and control of the structure of inverse opal and the composition of gas sensing materials,the effect of inverse opal structure on the response performance of gas sensing materials was studied in detail,and the metal oxide gas sensing materials with excellent properties were obtained.The following are the main contents of the research work:1.The polystyrene?PS?microsphere emulsion with regular morphology and uniform particle size was prepared by emulsion polymerization,and the corresponding PS opal template was constructed by heating evaporation self-assembly method.Then the inverse opal structure WO₃,Pt O₂/WO₃,SnO₂and Zn O/SnO₂gas sensing materials were prepared by filling the precursor and burning the template.At the same time,pure WO₃and SnO₂nano-powders were prepared by thermal decomposition method.2.The gas sensing properties of pure WO₃,inverse opal WO₃and inverse opal Pt O₂/WO₃to acetone were studied.At the working temperature of 45?,the sensitivity of pure tungsten oxide powder to 50 ppm acetone is 9.2,the response/recovery time is 10/25 s.the sensitivity of inverse opal WO₃to 50ppm acetone is 13.8,the response/recovery time is 7/12 s.When the composite ratio of Pt⁴⁺is 0.2%?mol/mol?,the inverse opal WO₃?marked as 0.2%Pt/IO-WO₃?has the best response to 50 ppm acetone,its sensitivity is 17.3,which is almost double that of pure tungsten oxide,and the response/recovery time is 5 s and 7 s,and its speed is greatly improved.It is found that 0.2%Pt/IO-WO₃has high response to acetone gas and very fast response/recovery.3.The gas sensing properties of simple SnO₂,inverse opal SnO₂and inverse opal Zn O/SnO₂,to ethanol were studied.Among them,the optimum working temperature of simple SnO₂is 310?,the response value to 50 ppm ethanol is 12,and the response/recovery time is 19/29 s.while the optimum working temperature of inverse opal SnO₂is 198?,the response value to 50ppm ethanol is 80,and the response/recovery time is 8/19 s.When the compound ratio of Zn²⁺is 8%?mol/mol?,the inverse opal SnO₂?marked as 8%Zn O/IO-SnO₂?has the best response to ethanol of 50 ppm.The optimum operating temperature is 198?,the response value is 202,and the response/recovery time is 6/9 s.Inverse opal structure and heterojunction structure play a great role in improving the gas sensing performance.8%Zn O/IO-SnO₂not only has a response value of nearly 20 times that of simple SnO₂,but also has a very high response/recovery speed.