| When the remarkable achievements are made in economic construction,the problem of environment is becoming more and more serious.Nitrogen dioxide is a kind of air pollutant,the real time detection to NO2 is very necessary,and it is of great significance to environmental protection.With the development of science,technology,environmental protection and other fields,new gas sensor of high sensitive is widely followed.Compared with the traditional gas sensors,the new sensor with the characteristic of high sensitivity,small,portable,real-time analysis,facilitate batch manufacturing,etc.The researchers in many countries are attracted to graphene when it became available in 2004.As a kind of new materials,graphene has high conductivity and large specific surface area,can be generated between it and the adsorbate with strong interaction.Compared with other carbon structure,such as carbon nanotubes,graphene has smaller energy gap,which makes the noise very low,concentration of current-carrying subtle changes can cause a significant change in the conductivity.Graphene has potential for gas sensing properties,empowering it with high potential application value in the high sensitive gas sensor.The main work of this paper is as follows:1.Three common gas detection methods are researched,the advantages and disadvantages are analyzed,as well as the limitations when they are used as NO2 gas sensors.In recent years,many achievement are made on graphene NO2 gas sensors,however there are some problems need to be solved.2.The different quantization movement of NO2 molecule can be induced by the absorption of photon which wavelength is between 60 nm and 25?m.Owning to the interaction between electron energy level of NO2 molecule,the molecule can absorb photon continuously when its spectrum is in visible band,therefore phonon can affect the NO2 molecules absorbed on graphene.3.Graphene has many excellent physical properties,the special electrical property making graphene to be hot research material for NO2 gas sensor.The common methods to get graphene are studied,including their advantages and disadvantages,and the characterization methods are summarized to provide direction in the experiments.4.The basic physical properties of graphene and the electrical properties changes of graphene after it adsorbed NO2 molecules have been analyzed.The theoretically states that graphene can be used to the detection of NO2 molecules.5.Proper graphene samples are designed and made for the experiments,as well as the graphene gas-sensing properties experiment system,a small constant temperature device and smaller chamber system is designed to meet the demand of the experiments.6.The analysis and study of graphene on NO2 gas gas-sensing properties,response characteristics,response time and desorption properties have been carried out in the experiments.The response is very fast,while the recovery time is too long.Graphene is a kind of semiconductor material,with the concentration of NO2 gas increased,the resistance response of graphene is smaller.7.By changing the temperature of the graphene,the effect of temperature to the resistance,response,recovery process of graphene are studied.With the increase of temperature,both the resistance and response will also increase.In a certain temperature range,the recovery progress can be accelerated under higher temperature environment.8.The influence of illumination to graphene gas sensor is studied as well.The resistance and recovery progress will not be affected,if the light is under proper power,but the recovery time can be reduced.And with the wavelength of light increased,the recovery progress is faster.As a sensor,graphene need has the property of real-time gas adsorption and desorption,gas sensitive characteristic and response time are the key to the application as the sensor performance.The graphene gas sensitive response and desorption properties are studied with heating and illumination.And the theoretical is analyzed to explain the phenomenon.And the preliminary controlled work mode of graphene as a gas sensor is acquired. |
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