Application Of SnO₂ Semiconductor Gas Sensor On Rapid Detection Of Food Safety Hazards

"Hunger breeds discontentment,fresh to the first",food security is the foundation of human health.Today,the problem of food and clothing has been basically solved in our country,the food safety hazards may cause human health hazards are increasingly concerned.There are kinds of harmful factors in food,it can be divided into biological hazard,chemical hazard,physical hazard and other hazards.Among there,the most important harmful factors are microbial contamination and chemical hazards.As one of the four most common pathogens in food,L.Monocytogenes can grow and multiply in 4 ?,which is the main pathogen of human health in chilled food.In addition,Sulfur dioxide as one of the food additives,food safety accidents caused by abuse use of sulfur dioxide,also brings serious challenges to food quality and safety,human life safety.In order to solve these potential threats,establishment of effective food safety detection technology has become very important in the food industry.Metal oxide semiconductor gas sensor as a product of the development of science and technology,because of its advantages of simple preparation,low price,light weight and long service life,has been widely used in industrial production,environmental monitoring and other fields of human life,on the detection of flammable and explosive,toxic and harmful gases has been revealed fast,sensitive and efficient detection effect.Therefore,this study is to develop a semiconductor gas sensor for rapid and sensitive detection of L.Monocytogenes in milk and sulfur residue in tremell based on target gas 3-hydroxy-2-butanone and sulfur dioxide using gas sensing properties of SnO₂ nanoflower sensitive material.The aim of this study is to provide a simple,affordable,efficient and rapid detection technology for food safety.The main contents and results of this study are as follows:1.Synthesis of semiconductor metal oxide gas sensing materials and fabrication of1.Synthesis of semiconductor metal oxide gas sensing materials and fabrication of sensorsIn this chapter,three kinds of morphologies materials,SnO₂ nanoparticles,SnO₂ nanorods and SnO₂ nanoflowers,were successfully prepared by a simple,green and effective sol-gel and solvothermal method.The crystal structure and morphology of the prepared samples were analyzed by XRD,TEM and N2 adsorption desorption.The results show that the three samples prepared in this study are single SnO₂ phase with high crystallinity and purity.The SnO₂ nanoflower has a large pore structure and specific surface area,and its average pore size and specific surface area are 17.55,20.46,55.07 m2/g and 2.99,18.47,8.9 nm.2.Rapid detection of L.Monocytogenes in milk base on SnO₂ nanoflower gas sensorIn this chapter,the gas sensing properties of the sensor for 3-hydroxy-2-butanone standard gas and its effect on the detection of L.Monocytogenes in TSB medium and milk were analyzed.The results show that the sensor exhibited high response,quick response–recovery kinetics,and good repeatability for 3-hydroxy 2-butanone.Furthermore,the response showed a good linear relationship with the concentration of L.Monocytogenes,the linear regression equation was lg?S-1?= 0.1983 lg?C?-0.4725?R2 = 0.9901?,the detection limit up to 10 CFU/m L.This approach can be finished within a few times and requires no extensive sample preparation shows potential for future development as a rapid method for the detection of L.Monocytogenes in food.As the characteristic volatile metabolites produced by microorganisms during growth are not the same,and we can prepare Sensitive materials which according to the characteristic volatile metabolites.Therefore,this method can be used for other food pathogens detection.3.Rapid detection of sulfur dioxide residues in tremella based on SnO₂ nanoflower gas sensorIn this chapter established a sensitive gas sensor based on SnO₂ nanoflower for rapid detection of sulfites residue in tremella with sulfur dioxide as the detection marker.Infrared spectra was applied to delineate chemical profile variances of tremella through sulfur fumigation.Furthermore,the sensor performance of the as-prepared material for sulfur dioxide calibration gases were analyzed.Finally,a quantitative model to predict contents of sulfites residue was established based on SnO₂ nanoflower sensor.The results indicated that the main residue sulphur has been combust into hydrosulfite remained in tremella.The sensor exhibited high response,quick response–recovery kinetics,and good repeatability for sulfur dioxide,Response and recovery time are within 7 S,16 s.A good linear relationship was observed between the response of the sensor and the concentration of sulfite with a linear regression equation,lg?S-1?= 0.8563 lg?C?+0.02955?R2 = 0.9905?.This approach showed well potential to provide a simple,low-cost and sensitive method for rapid detection of sulfites residue in food.