Research On Acetone Gas Sensors Based On LaFeO₃ Micro/Nanostructure Materials

Acetone,as a good solvent and raw material,has been widely used in organic synthesis in modern industry.But acetone is also very easy to volatilize into toxic and irritant acetone vapor,which will explode if mixed with air.In addition,acetone is also a breath marker,which can be used to detect diseases such as diabetes and halitosis.Therefore,the detection of acetone with sensors is of great significance in industrial production,environmental monitoring,toxic gas leakage and disease diagnosis.Oxide semiconductor gas sensors have the advantages of small size,high speed and low cost compared with other detection methods.But how to create gas sensors with high sensitivity,high selectivity,fast response and high stability is still the primary challenge.According to the widely accepted theory,the main factors that affect the performance of oxide semiconductor gas sensors are the receptor function,the transducer function and the utility factor of the sensing body,which are closely related to the microstructures of sensing materials.Thus,it is a simple and effective method to improve the gas sensing properties of the materials by using structural advantages.As a typical perovskite composite oxide semiconductor,the research of LaFeO₃ gas sensing characteristics has also been a hot topic in the field of oxide semiconductor gas sensors.In this paper,template-free hydrothermal routes were used to prepare LaFeO₃ with different microstructures.Taking advantage of their structural advantages,the surface adsorption and diffusion of acetone gas molecules can be increased,so as to achieve the purpose of"enhance sensing performance".The main research contents are as follows:1.A simple hydrothermal reaction with a subsequent annealing process was used to prepare porous LaFe O₃ spheres.According to a series of characterization results,the diameters of the porous spheres are about 0.5¹?m,the average pore size is about32 nm and the pore volume is 0.09 cm³g^-1.The gas sensing properties of the gas sensor based on porous LaFeO₃ spheres were tested.The results revealed that LaFeO₃porous spheres showed high sensitivity and fast response to acetone at the optimum working temperature of 225?.In addition,in a one-month stability test,the response values of the gas sensor were floating at 12.7,which shows that the sensor has good stability.The porous structure is beneficial to the reaction and diffusion of gas molecules,thus enhancing the gas sensing properties of the material.2.A facile hydrothermal route with the subsequent annealing and chemical etching process to the synthesis of yolk-shell LaFeO₃ microspheres without any template is described.The evolution process of yolk-shell structure was observed by transmission electron microscopy?TEM?.Based on that,the formation mechanism was proposed.Indirect-heated gas sensor devices were fabricated from the as-prepared samples,and their gas sensing properties were tested for response to various reducing gases.The test results showed that the yolk-shell LaFeO₃microspheres had higher sensitivity than the other two structures.At the optimum working temperature of 225?,the yolk-shell LaFeO₃ microspheres also showed good selectivity and outstanding response and recovery characteristics,and the detection limit could be as low as 1 ppm.In addition,the response values were almost stable during the 30 days'test.The excellent acetone gas sensing properties of the yolk-shell microspheres benefit from their unique structure.The large specific surface area can provide more active sites,which is conducive to the adsorption and reaction of acetone.Meanwhile,the good permeability can also enhance the utilization rate of the sensing body.