Study On Gas Sensing And Photoelectric Properties Of Molybdenum-Based Compounds

In the past two decades,with the development of economy,the whole world is suffering from different crises,such as water crisis,power crisis,energy crisis and environmental crisis.In order to solve these crises and meet the current environmental monitoring needs of the world,we need not only afforestation,but also future development.Based on photodetectors and gas sensors,they are sensors used to detect gas components in the environment.They can detect harmful substances in the air and convert them into electrical signals,which can be recorded in a computer to achieve accurate detection of pollutants in the environment.Therefore,it is crucial to prepare excellent photodetectors and gas sensors.The performance of devices is usually evaluated using parameters,which are determined by the structure of the device and more importantly,by the detection material.Molybdenum based compound materials have attracted widespread attention due to their excellent conductivity,stable structure,simple preparation,and low cost.Molybdenum sulfide（Mo S₂）has a small band gap（1.2 e V-1.9e V）and a wide spectral absorption range,so it is an excellent material for preparing photodetectors.Mo O₃ has been widely used in gas sensing field because of its high stability,broadband gap and special lamellar structure.So this article,Mo S₂ nanotubes and Mo O₃ powders using template and grinding methods,and assembled into photodetectors and gas sensors to study their corresponding photoelectric and gas sensing properties.The content is as follows;In this paper,ordered PVP nanowires were first prepared by electrospinning,and then molybdenum sulfide was deposited by Pulsed laser deposition（PLD）to form one-dimensional ordered PVP/Mo S₂ nanocomposites with core-shell structure.The deposition process controls its time to form Mo S₂ layers of different thickness.Then,annealing at 350℃was conducted in a tubular furnace under nitrogen atmosphere to remove PVP and form Mo S₂ nanotubes.Finally,a Mo S₂ nanotube photodetector was fabricated using interdigital electrodes,and its photoelectric performance was tested using Giselli 2612B testing software.The results showed that the device made of ordered Mo S₂ nanotubes exhibited good detection efficiency and quantum efficiency for visible light at 405 nm wavelength.The lamellar Mo O₃ crystal was prepared by thermal evaporation method,and the size of Mo O₃ was reduced by cutting and grinding.It was found that the color of the sample would change with the change of grinding time,Therefore,change the grinding time（0.5 h,1 h,2 h）to determine its excellent performance.In order to eliminate the impact of moisture in the air on it,choose to grind it for 2 h in an argon filled and oxygen free environment,and analyze its morphology,specific surface area,and defects through a series of characterization.Finally,gas sensitivity tests were conducted on different samples,and it was found that Mo O₃ had the best selectivity for ethanol gas,and the samples ground for 1 h had higher sensitivity.Therefore,the mechanism of ethanol gas sensitivity was discussed and the changes in gas response with defect concentration and specific surface area were studied.