Research On The Effects Of Noble Metal Surface-decorating And Doping On Gas Sensing Properties Of Oxide Semiconductor

With the continuous development of society and technology,people pay more and more attention to the quality of life.In our daily life,there will be some toxic,hazardous,flammable and explosive gases which cause damage to environment and human health.At this time,gas sensor will play a very important role to detect the toxic gases timely.Nowadays,researchers are committed to the development of gas sensors with good gas sensing property,such as fast response and recovery and high selectivity.Among these gas sensors,metal oxide semiconductor gas sensor is one of the most important ones.It has the advantages of simple process,low cost and high gas-sensing properties.Nowadays,people use different ways to synthesize oxide semiconductor materials.However,there are some defects in the application of pure oxide semiconductor materials in gas sensors,such as low response,slow response and recovery speed and poor selectivity.Therefore,people use many methods to get better performance,such as changing material morphology,doping,surface-decorating and composite materials.In order to improve the gas sensing properties of the gas sensor,we use the noble metal to dope or surface-decorate the oxide semiconductor in this paper.And The chemical and structural characterizations of materials are performed with various techniques such as X-ray diffraction?XRD?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?and Energy Dispersive X-Ray Spectroscopy?EDX?.This paper mainly includes the following three parts:Firstly,SnO₂ nanofibers are fabricated by an electrospinning method,and Au nanoparticles are decorated on the surface of the nanofibers by a water bath and heating treatment process.Meanwhile,their formaldehyde?HCHO?sensing properties are investigated in detail.Compared with SnO₂ nanofibers,the response of Au-SnO₂ material is twice as much as that of pure SnO₂,and it has lower operating temperature and better selectivity.Secondly,Ag-doped LaFeO₃ nanofibers are synthesized by electrospinning method.We compare the gas-sensing properties of the different materials to find the best Ag doping ratio.The experimental results indicate that the sensor based on the sample Ag-La FeO3 shows excellent gas sensing properties to formaldehyde.Among these Ag-doped LaFeO₃ sensors,the response of 2 mol% Ag-doped sensor is the best.It has the response of 20 to 100 ppm HCHO and the minimum detectable concentration limit of HCHO gas can reach 5 ppm.Meanwhile,the detection process can be completed within five seconds.It also has the better selectivity.Then the mechanism of Ag doping to improve gas sensor is explained in this paper.Thirdly,SnO₂ octahedral material is synthesized by hydrothermal method and Au nanoparticles are decorated on the surface of the materials by a water bath and heating treatment process.Compared with pure SnO₂ octahedral material,Au-decorated ones have the better response,it has the response of 33 to 100 ppm acetylene?C₂H₂?and the minimum detectable concentration limit of C₂H₂ gas can reach 1 ppm.And the operating temperature of the device is greatly reduced by decorating Au nanopartiles.The material showed good gas sensing properties of acetylene.