Investigation On The Two-Dimension Metal Sulfide Nanostructures Based Gas Sensors At Low Temperature

Due to its large specific surface area and controllable electronic properties,twodimensional metal sulfides have shown unlimited application potential in the field of gas sensing,and become a new hot material for research in ths field.Although the metal sulfide gas sensor overcomes the problem of high working temperature of the traditional metal oxide gas sensor,it still has the problems of slow response/recovery rate and difficulty in detecting at room temperature.Therefore,This paper focuses on n-type metal sulfide SnS2 as the main body of the research,and replaces the traditional thermal excitation mode with light radiation to solve the problem that SnS2 sensitive materials are difficult to detect gas at room temperature;The enhancement characteristics of light radiation on gas sensitivity of p-type metal sulfide WS2 at room temperature were investigated,and a self-powered light-assisted gas sensor was developed.The gas sensing performance of metal sulfide SnS2 was improved by using homotype heterojunction and noble metal doping modification.On the basis of experiments,combined with the first-principles density functional theory,a two-dimensional gas adsorption model of metal sulfide SnS2 and precious metal/metal sulfide was constructed,and the gassensitive adsorption mechanism of metal sulfide and its composites was expounded.The specific research contents are as follows:1.Investigate the effect of optical radiation as an external excitation source to enhance the gas-sensitivity properties of two different conductivity types of metal sulfides.Taking n-type metal sulfide as the main research subject,a systematic comparison of the effects of two different external excitation sources,optical radiation and thermal excitation,on the gassensitive performance of metal sulfide.The gas sensitivity enhancement characteristics of metal sulfides under different wavelengths and different light radiation intensities were further explored,and the sensing mechanism of the light-excited gas sensor was elaborated on this basis,which solved the difficulty of SnS2 to realize gas detection at room temperature.Based on the experiment and combined with density functional theory,the intrinsic SnS2 and S-hole SnS2 adsorption models were established.The gas-sensitive adsorption mechanism of metal sulfide was explored on the theoretical calculation.The concept of TENGs was applied to develop the self-powered light-assisted gas sensors by using p-type metal sulfide WS2 as the matrix material.The sensor's gas-sensing test data shows tha the incident light at 365 nm not only improves the characteristics of the metal sulfide itself,but also may promote the electronic transition of NH3 molecules to the surface of the material,which is beneficial to the improvement of gas sensing performance of WS2-based sensor.2.Inveatigate the effect of heterojunction composite materials on the improvement of gassensitive performance of metal sulfide sensitive materials.The in-situ oxidation method was used to modify the metal oxide SnO2 nanoparticles on the surface of the two dimensional metal sulfide SnS2 to prepare n-n-type SnO2/SnS2 homo-heterojunction composite materials,and explore the influence of the number of interface bonds on the gas-sensing properties of composite materials under the different oxidation time and the oxidation temperature preparation conditions,.On the basis of experiments,the enhancement mechanism of the gassensitivity of metal sulfides with the same type and heterogeneous structure was explained.3.Investigate the effect of nobel metal doping on the improvement of gas-sensitive performance of metal sulfide sensitive materials.Based on the synergistic effect of the"electronic sensitization" and "chemical sensitization" of noble metal nanoparticles,a one-step reduction method was used to prepare noble metal/metal sulfide,which overcomes the shortcomings of low response recovery rate of metal sulfide gas-sensitive materials.Based on density functional theory,a new calculation model of noble metal/metal sulfide(Au/SnS2)adsorption system is proposed,which provides a favorable theoretical support for the gassensitive adsorption mechanism of noble metal doped metal sulfide.