Research On Metal Oxide Gas Sensor Based On Prussian Blue

In recent years,due to the urgent needs of air quality monitoring,industrial production emission monitoring,toxic gas monitoring,medical diagnosis,the research of gas sensors has received extensive attention.Among them,metal oxide semiconductor resistance gas sensors have been one of the mainstream research directions in the field due to their low cost,high sensitivity,good reliability and easy operation.Sensitive materials are the foundation and core of gas sensors.The gas sensing properties of the sensor are closely related to the morphology,microstructure and chemical composition of the material.At present,many studies are devoted to the development of new methods and techniques to obtain higher performance sensitive materials.Studies have shown that the preparation of metal oxides using metal-organic frameworks(MOFs)as precursors can effectively control the parameters such as morphology and microscopic composition,and then optimize the gas sensing properties of the materials.Based on the simple structure and easy regulation of Prussian Blue(PB),this paper prepares Fe2O3 and its composites as precursors.In the early stage,the influence of the conversion temperature on the gas sensing performance of the oxide was studied on the basis of the flower-like Prussian blue.Then the Prussian blue of the cubic and spherical morphology was designed and prepared,and the gas-sensitive behavior was studied.Finally,for the first time,by constructing a heterojunction structure with Cu4O3,the working temperature of the material is lowered,and the sensitivity and selectivity of the material are greatly improved.The main research contents include:The nanoflower-like Prussian blue was obtained by hydrothermal method at 80 ? by the control of surfactant N-N dimethylformamide(DMF),which was calcined at 350? and 550? respectively.Two kinds of gas sensitive materials,Fe2O3-350 and Fe2O3-550,were obtained,and the difference of gas sensing behavior between the two materials was studied.Studies have shown that the materials obtained at both temperatures can maintain the morphology of the original material well and exhibit a multi-stage structure.Gas sensitivity tests found that Fe2O3 obtained at higher temperatures(550?)has better gas sensitivity.The optimum operating temperature for both is 200?.However,the response of Fe2O3-550 to 5 ppm hydrogen sulfide(H2S)was 12.83,which was significantly greater than Fe2O3-350(7.54 response to 5 ppm H2S).The response-recovery time of both is at the minute level,the response time is 4.95 and 4.88 minutes,and the recovery time is 18.28 and 16.59 minutes.Selective testing of different gases showed that Fe2O3-550 has good selectivity properties.At the same time,the material is able to maintain good working stability over a wide range of relative humidity fluctuations.Subsequent tests found that Fe2O3-550 also performed well at the ppb level and exhibited a linear response relationship indicating the ability to quantitatively detect ppb levels.In addition,Fe2O3-550 has a good performance in terms of repeatability and reproducibility.Prussian blue with two different morphologies of nanospheres and nanocubics was obtained by the synthesis temperature(80?,140?)and the control of surfactants.After heat treatment at 550?,two kinds of Fe2O3 were obtained to maintain their original morphology,and the sensor device was prepared as a sensitive material.Through the self-made gas sensitivity test system test,it was found that the optimum working temperature of the two materials was 200?,and the response to 5 ppm of H2S was 30.8 and 22.2,respectively.The response time was 2.44 and 1.85 minutes,respectively,and the recovery time was 6.09 and 9.1 minutes.Compared with the aforementioned materials,there has been a great improvement.And both topographical materials have good selectivity.Especially for the interference of water molecules,it shows strong tolerance,and it works well even under high humidity conditions.Both materials show excellent monitoring of ppb concentration H2S and have quantitative detection conditions.At the same time,it has excellent performance in terms of repeatability and long-term stability.Overall,it is better than the current domestic and intermational reports based on the detection performance of pure phase Fe2O3 sensor for H2S.The nanocubic Prussian blue was selected as the research object,and the composite material Cu4O3/Fe2O3 with heterojunction structure was constructed by hydrothermal method combined with copper acetate.Four materials(0,1:10,1:15,1:20)were prepared according to the ratio of Cu:Fe,and the gas sensor was prepared and tested for systemic gas sensitivity.Studies have shown that the material has the best gas sensitivity when Fe:Cu is 1:15.Compared with the gas-sensitive material prepared above,the working temperature of the material is reduced to 100?,and at the same time its response to 2 ppm H2S reaches 59.23,and the sensitivity is greatly improved compared with the pure phase Fe2O3.Moreover,it has more excellent selection performance,and does not substantially respond to 100 ppm of acetone,ammonia gas,sulfur dioxide,and the like.At the same time,the material still maintains good performance at the ppb concentration level and has the ability to detect low concentrations of H2S.