Study On Preparation And Properties Of Gas Sensor Based On Iron Oxide Nanomaterials

With the improvement of technology and people’s safety awareness,gas sensors play an increasingly important role in environmental protection,industrial safety supervision,smart home and medical care.Among them,the conductivity gas sensor based on semiconductor metal oxide,as the most widely used sensor,has the advantages of low cost and outstanding gas sensing detection performance.Fe₂O₃ semiconductor nanomaterials have excellent characteristics such as high conductivity and high catalytic activity,as well as high research value,making them stand out among many metal oxides in the field of gas sensors.In this project,iron oxide-based gas-sensitive materials and gas sensors are mainly studied.The main research work of this thesis is as follows:（1）γ-Fe₂O₃ with typical high response to ethanol andα-Fe₂O₃ nanomaterials with high response to acetone were prepared by solvothermal method and hydrothermal method combined with orthogonal test method,respectively.The two Fe₂O₃ materials synthesized by the optimal experimental protocol were explored and analyzed by SEM and XRD characterization methods,and it was found that they were composed of spheroid and rod nanoparticles with good dispersion,respectively,and the crystal structures were verified to beαandγtypes,respectively.The gas sensitive performance test of Fe₂O₃ materials was carried out,and the gas sensor based onγ-Fe₂O₃ nanospheres showed high selectivity and high response to ethanol at an operating temperature of 260°C.Theα-Fe₂O₃ nanorod gas sensor exhibits excellent gas sensing performance of acetone at 240°C.（2）Based on the prepared pureγ-Fe₂O₃ nanospheres,Au-loadedγ-Fe₂O₃ gas sensing materials were prepared by amino acid synthesis to improve the gas sensing performance of the sensor.Different characterization methods were used to explore the microstructure and other information of product materials.Through many gas sensitive test experiments,the sensing performance of pureγ-Fe₂O₃ and Au-loadedγ-Fe₂O₃ materials on ethanol was compared and analyzed.The results show that the gas sensitivity performance ofγ-Fe₂O₃nanospheres to ethanol after loading Au particles is significantly improved,and the sensor based on the composite shows a lower operating temperature（200°C）and a higher response value of 56.7.According to the mechanism analysis,the electronic and chemical sensitization effects of Au nanoparticles are the main reasons for improving gas sensing performance.（3）Based on the prepared pureα-Fe₂O₃ nanorod gas sensing materials,Zn O/α-Fe₂O₃heterojunction composites were prepared by solvothermal method to improve the gas sensitivity performance of the sensor to acetone.The effective binding ofα-Fe₂O₃ to Zn O particles was confirmed by characterization methods.The results of gas sensing experiments show that compared with pure Zn O andα-Fe₂O₃,the gas sensor based on Zn O/α-Fe₂O₃（S-2）shows better gas sensing performance for acetone,and has a higher response value（62.8/100ppm）and a faster response/recovery time（4s/10s）for acetone at 220°C.According to the mechanism analysis,the unique structure of Zn O/α-Fe₂O₃（S-2）material and the n-n heterojunction effect enhance the gas sensitivity performance of the sensor to acetone.（4）Bythermal ethanol sensor and acetone sensor were prepared based on the synthetic Au-loadedγ-Fe₂O₃ and Zn O/α-Fe₂O₃ high-performance composite nanomaterials,and the gas monitoring device was designed and manufactured with these two gas sensors as the core components and their functions were tested.Starting from the overall architecture of the gas monitoring device,the hardware circuit and software system design of the device are introduced in detail,and the physical production of the device and the construction of the experimental environment are completed.The prepared monitoring device and the ION handheld VOC gas detector on the market jointly detected the concentration of ethanol and acetone,and the results were compared and analyzed,which verified the good reliability and practical application potential of the gas monitoring device designed in this paper.