Investigation On Preparation And Sensing Mechanism Of Gas Sensors Based On Two-dimensional Tellurene

The demand for high-performance gas sensors in environmental protection,industrial manufacturing and medical health,etc.is increasingly urgent.Since graphene was prepared by mechanical exfoliation for the first time,two-dimensional(2D)materials are considered as ideal gas sensing materials due to their large surface volume ratio and rich surface active sites.However,some inherent disadvantages of the intrinsic2 D materials,such as the semi-metallic properties of graphene,the more point defects and low carrier mobility of MoS2,the environmental instability of black phosphorus and the wide band-gap characteristics of h-BN,make them not an ideal gas sensing material for gas detection.In this thesis,the gas sensing performance of a new 2D material,tellurene,is explored from the micro-mechanism,and a low-cost and high-performance NO2 sensor based on tellurene is obtained through experiments.The research results are mainly summarized as follows:(1)Firstly,gas sensing mechanism of 2D tellurene for detecting SF6 decomposition components(HF,SOF2,SO2,SO2F2 and H2S)is studied by means of first-principles calculations.The nearest atomic distances between tellurene and gas molecules and the electronic local function(ELF)of the adsorption system indicate that there is a physical interaction between 2D tellurene and gas molecules.The calculated adsorption energy and charge transfer reveal that tellurene exhibits weak adsorption interaction to SO2F2,HF and H2 S molecules,while showing moderate adsorption energy(-0.382 eV and-0.352 eV)and obvious charge transfer(-0.158 e and-0.093 e)to SO2 and SOF2 molecules.Meanwhile,the calculated density of state(DOS)and charge density difference(CDD)indicate that the electrical properties of the whole system have changed significantly after SO2 and SOF2 molecules adsorption.These phenomena indicate that 2D tellurene has an important application potential to the detection of SF6 decomposition for the insulation and stability in high-voltage insulation equipment.(2)In addition,first-principles calculations method is performed to study the feasibility of tellurene detecting NO2 gas in the air environment.The calculated Bader charge transfers and CDD reveal that the interface electrons of NO2 / tellurene system transfer from tellurene to NO2 molecule.When NO2 is adsorbed on 2D tellurene,the hole density of tellurene increases significantly.Also,the band structure is split after tellurene adsorbing NO2:spin-up and spin-down band gaps both obviously get narrower.Meanwhile,the calculated ELF visually screens that there is no overlap of electron localization between 2D tellurene and NO2 molecule,indicating a physical adsorption interaction.These results provide a sensing mechanism explanation for the preparation of a new generation of NO2 gas sensor.(3)Finally,the nano-sized tellurene thin films are fabricated by liquid phase exfoliation method and is characterized by AFM,TEM,HRTEM and Raman analysis,etc.The results of gas sensing test indicate that the tellurene sensor possesses a significant response of 264.3% at 150 ppb of NO2 concentration and an ultra-low theoretical detection limit of 0.214 ppb for NO2 detection.In addition,the tellurene sensor can achieve rapid response and complete recovery at ppb level of NO2 concentration.Meanwhile,the tellurene sensor exhibits excellent stability when the temperature is up to 100 ?.These excellent performances reveal that tellurene sensor can detect NO2 rapidly and efficiently in complex atmosphere.