Study On Preparation And Acetone Sensing Properties Of The Mesoporous NiFe₂O₄

The preparation of materials with excellent acetone gas sensitivity is conducive to environmental monitoring and early diagnosis of diabetes.In recent years,the application of Ni Fe₂O₄（NFO）with a spinel structure as a gas-sensitive material has received extensive attention.Adjusting the pore structure of materials and precious metal modification are effective approaches to further improve sensitivity,selectivity and stability.In this paper,mesoporous NFO was prepared by the template method and the template-free method to optimize the sensing properties to acetone detection.The sensing performances of the material was greatly improved by adjusting the microscopic morphology,pore structure of the mesoporous NFO,as well as the noble metals functionalization.Furthermore,the sensing mechanism to acetone detection was discussed in details.The main contents of this paper are as follows:（1）Synthesis of mesoporous NFO by template to acetone detectionSBA-15 and P123 were used as hard and soft templates to successfully synthesize ordered and disordered mesoporous NFO,and their gas sensing properties were studied.More active sites and channels for gas reaction are provided due to the unique mesoporous structure and large specific surface area,thus the gas sensors based on the as-prepared NFO exhibits high sensitivity,lower detection limit,fast recovery and response,excellent selectivity and stability.Especially,the mesoporous NFO synthesized by the soft template shows a disordered mesoporous structure,leading to easy conducive for gas molecule diffusion.At a working temperature of 210 ^oC,the response value to 200 ppm acetone is57.A good linear relationship between response and acetone concentration is observed in the range of 1 ppm to 200 ppm.（2）Template-free synthesis of mesoporous NFO for acetone detectionUsing NTA as the chelating agent,the mesoporous NFO nanorods were successfully prepared by the hydrothermal method combined with the subsequent heat treatment process.It is found that the amounts of NTA in precursor play an important role on morphology,specific surface area and sensing properties of the products.In particular,the NFO possesses a larger specific surface area of 197.1 m~2/g when the amount of NTA is 3 mmol.At the optimal working temperature of 200 ^oC,the response value to 200 ppm of acetone reaches 64.The analysis believes that the high sensitivity is not only due to the large specific surface area,but the small particles dispersed in the material provide more channels for gas diffusion.The sensing properties are further improved by Pt functionalization mesoporous NFO,which shows 1.6 times response than that of pure NFO and much faster response recovery time,which is attributed to the excellent catalysis of the Pt nanoparticles.In short,the preparation routes for mesoporous NFO,the strategies for pore structure control and the influence on the detection of trace acetone gas have been studied.These findings will open a new window for the research of mesoporous nickel ferrite and the improvement of sensing properties.