Research On Gas Sensors Based On Nickel Ferrite For Acetone Detection

Prolonged exposure to acetone may cause a variety of negative physiological effects,such as vomiting,cramping,coma,central nervous system anesthesia,and liver damage.In addition,medical diagnostic studies have shown higher concentrations of acetone in the exhaled air of diabetic patients than in healthy people.Therefore,in order to ensure personal safety and early diagnosis of diabetes,it is of great scientific significance to develop an efficient gas sensor to detect trace acetone.Oxide semiconductor gas sensors have been a research hotspot in the field of gas sensors due to their advantages of small size,integration and on-line detection.Due to their high catalytic activity and flexible and adjustable chemical properties,AB₂O₄spinel oxides are gradually used as sensitive materials in gas sensors.However,their detection limits,sensitivity and selectivity are difficult to meet the actual needs.In view of the above problems,this paper takes NiFe₂O₄ as the sensitive material,and improves the sensitivity to acetone and reduces the detection limit by optimizing its microstructure and permeability.The main research contents are as follows:The litchi-like NiFe₂O₄ sensitive material was successfully synthesized by solvothermal method and subsequent annealing process.The results of SEM and TEM characterization showed that the litchi NiFe₂O₄ microsphere is about 500 nm in diameter,with a rough and loose shell and a thickness of about 35 nm.The synthesized microspheres used as sensitive materials were coated on the ceramic tube and made into a side heat gas sensor to test its gas sensitivity.The test results showed that the litchi NiFe₂O₄ sensors showed a high response to 100 ppm acetone at 200℃,and the response was fast,and the sensors still showed a significant response in 1 ppm acetone atmosphere.In the cycle test,the responses of the sensors were maintained around 8.6,with a small floating range,indicating that they had good repeatability.Better acetone sensitivity is due to the shell structure providing more channels and more active sites for acetone gas molecules,which is conducive to a greater degree of contact between gas molecules and sensitive materials and further interaction to generate electron exchange,thus improving the sensor sensitivity.The porous structure NiFe₂O₄ microspheres were successfully prepared by one-step solvent-heat method combined with subsequent annealing treatment,and the lower limit of detection is expected to be further reduced by taking advantage of its micro-nano structure.The results of electron microscopy showed that the NiFe₂O₄microspheres were self-assembled by nanoparticles with a size of about 10 nm,evenly dispersed,with a rough surface and a diameter of about 150 nm.In addition,BET test results showed that the pore diameter of the material was about 8.9 nm.The porous material was fabricated into a side heat gas sensor and its gas sensitivity was tested.The porous NiFe₂O₄ gas sensors show high response,good anti-interference,fast response speed and good long-term stability to 100 ppm acetone at 250℃.Moreover,the response of the sensors in the atmosphere of 20¹00 ppm acetone showed an approximate linear increase.It is worth noting that the porous NiFe₂O₄ gas sensor still has a significant response value to 200 ppb acetone（1.3）,which is lower than the level of acetone gas exhaled in diabetic patients（1.8 ppm）.The excellent acetone sensitivity is attributed to the catalytic performance of NiFe₂O₄ material and its porous structure,which provides a convenient channel and reaction field for gas diffusion and reaction,increases the utilization rate of the sensitive body,and thus improves the sensitivity and detection limit.