Preparation Of Of Semiconductor Oxide-supported Nano Gold Particles And Their Gas Sensing Properties

At present,environmental issues have received wide attention from all walks of life.“Jinshan Yinshan is not as green as green mountains.”Solving environmental problems depends not only on the appeal of the humanities in protecting the environment,but also on the research of environmental protection by scientific researchers.The gas sensor is an environmental monitoring device used to detect dangerous poisonous gases.It plays a vital role in environmental protection,especially in the atmospheric environment.The gas sensor of the semiconductor metal oxide type has the advantages of low price and mature preparation method,and has become a relatively common type of sensor in the market.However,due to the characteristics of pure metals,pure metal gas sensors have the disadvantages of low monitoring response and poor selectivity,which greatly limits the application of this type of gas sensor.Therefore,it is important to seek a breakthrough point in this issue.The heterostructure structure of the metal oxide metal-metal/metal oxide loading structure is constructed.The structure,electrons and chemical effects of different metals can greatly improve the gas sensitivity of the semiconductor metal oxide to solve the above problems.In this direction,this paper mainly carried out several work:?1?Preparation of nano-Au particles by sol-gel method,selecting the optimum ratio of reducing agent to Au sol to achieve high dispersion and small particle size of Au;?2?Three kinds of semiconducting metal oxides WO_2.6,CeO₂ and TiO₂ were selected for Au particle loading.A simple and universally applicable method for preparing metal oxide powder-loaded nano-Au particles was used,and the amount of Au sol was carefully studied.The effect of stirring time and calcination temperature on the loading rate of nano-Au particles supported by metal oxide powder;?3?The loading mechanism of nano-Au particles supported on metal oxide powder was analyzed by TEM,HRTEM,HAADF-STEM and other electron microscopic characterization methods.In-situ experiment of semiconducting metal oxide CeO₂ with high oxygen vacancies;?4?The gas sensing properties of WO_x,CeO₂,TiO₂ and their loading on ethanol,formaldehyde and acetone gases were tested.Through the above work,the following conclusions are drawn:?1?Develop a simple,universal method for the successful preparation of Au nanoparticle-loaded metal oxide semiconductor material systems.The TEM results showed that the Au nanoparticles were inlaid with the metal oxide semiconductor material in a flat bottom surface,and did not fall off after 24 hours.The amount of Au sol added,the reaction time,and the calcination temperature are controlled to obtain a system having an optimum loading ratio.The method is simple,universal,easy to control,and easy to mass produce and commercialize;.?2?Successfully constructed a heterostructure system for the load and successfully improved the gas sensing properties of the metal oxide semiconductor.Through comparative experiments,it was found that the sensitivity,response/recovery time,stability and continuous detection of the metal oxide semiconductor material after loading were improved.The optimal operating temperature of the loaded purple tungsten is 240?,the highest sensitivity is 12.5,the response/recovery time is 6 s/21s;and it has good selectivity to ethanol.The optimal operating temperature of titanium oxide after loading is 320?,the highest sensitivity is 12.8,the response/recovery time is 12 s/38 s;and it has good selectivity to acetone;?3?For the first time,a two-dimensional tungsten oxide material was used for gas sensitivity testing to enhance its conductivity.And the gas-sensitive characteristics of three kinds of tungsten oxides with different degrees of oxygenation were tested for the first time.It was found that the purple oxygen oxide with the most under-oxygenity in25-400 ppm ethanol gas and 25-200 ppm formaldehyde gas has better gas sensitivity than other materials.The optimal working temperature of purple tungsten is 200?,the highest sensitivity is 7.35,the response/recovery time is 7 s/30 s,and it has good selectivity to ethanol;?4?Experiments have confirmed that the gas-sensitive properties of metal oxide semiconductor materials are related to the content of oxygen vacancies.The specific mechanism needs further study and verification.