| What water is to fish, that air is to us. With the continuous improvement of the level of industry, air quality is worsening. Air pollution is more serious harm to people, and it is urgent to solve the problem of. At present, the State Environmental Protection Department announced that the first row is PM2.5 in the major air pollutants, the second is the volatile organic compounds (VOCs). VOCs are the major pollution source of ozone pollution and photochemical pollution, and it is an important component of air pollution. Therefore, the detection and control of VOCs are an important way to control air pollution. Because the semiconductor gas sensor have the advantage of low cost, making simple, small size and light, etc. So that it is widely used in the field of gas sensing applications. But it also has many disadvantages, such as requires a higher operating temperature, poor selectivity, lower detection limit. These seriously hindered the application of metal oxide sensors in the field of precise detection. With the continuous progress of preparation technology and the emergence of new materials, such as nano-technology and the new appear of graphene materials in recent years. It provides the possibility for the application of semiconductor gas sensor in the field of precision measurement. Especially graphene has excellent physical and chemical properties so that it has great potential in the development of new gas sensors.This paper studied the prepared material and the gas sensing properties of noble metal/metal oxide/graphene ternary nanocomposites and analysis sensing mechanism of the ternary nanocomposites. The experimental materials of Au, Ag are selected in noble metals and SnO2 selected in metal oxides. Graphene oxide was prepared by a modified Hummers’method and then the prepared was annealed to graphene. The main experiment can be divided into four parts: The first is the preparation of graphene oxide materials used in the experiment using the modified Hummers’method. The second is the use of wet chemical method to prepare doped with different amounts of noble metal (Au, Ag)/SnO2/graphene precursor ternary composites, and under an argon atmosphere heat treatment at 300 ℃for 2 hours. The third part is the use of the prepared material for gas sensor. The fourth part prepared materials characterized by transmission electron microscopy (TEM) and energy dispersive spectrum (EDS),then the sensitive property of the sensor is tested. In the process of experiment by adjusting the amount of composite material of precious metal (Au, Ag) and gas sensing properties of materials testing to determine two ternary composites suitable amount of noble metal doped. The characterization of the materials showed Au or Ag nanoparticles present in the ternary nanocomposites. The test results of the gas sensing properties of Ag/SnO2/G ternary nanocomposites prepared by appropriate amount Ag doped. The working condition of the Ag/SnO2/G sensor is compared at different temperatures, and the optimum operating temperature of the sensor is found at 300 ℃. The synthesized ternary nanocomposites show higher sensitivity to VOCs, especially acetone. The lowest detect concentration to acetone is 0.005 ppm, and the detection range of 0.005-3000ppm, the response and recovery time is shorter. The test results of the gas sensing properties of Au/SnO2/G ternary nanocomposites prepared by appropriate amount Au doped. The ternary nanocomposites exhibited the remarkable selectivity to formaldehyde and the lowest detection concentration to formaldehyde is 0.1 ppm, and the detection range of 0.1-400ppm,and the optimum operating temperature of the sensor at 300 ℃. |
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