Development Of Semiconductor Metal Oxide Gas Sensor And Application In Meat Freshness Detection

With the improvement of living standards,people have higher requirements for meat freshness,which leads to the research of various meat freshness detection and evaluation equipment.Based on the high-performance gas sensor,a fast and nondestructive small gas detection system is established to detect the freshness of meat in different environments,which can significantly improve the safety of meat consumption for consumers.Aiming at the detection of characteristic gases（including NO₂ and H₂S）released by meat during storage,a gas sensor with high response is developed in this paper.A set of convenient and miniaturized meat freshness detection system is constructed to realize the rapid and nondestructive detection and evaluation of freshness in the process of meat storage.The main research contents of this paper are as follows:（1）Cu O-Co₃O₄ nanospheres with hierarchical structure were prepared by hydrothermal method and high-temperature sintering.By adjusting the synthesis ratio of Cu and Co,the hierarchical structure induced the enrichment of lattice oxygen,so as to improve its gas sensing characteristics for NO₂ gas.At the optimum operating temperature of 160℃,the response of Cu O-Co₃O₄ nanosphere to 10 ppm NO₂ gas is 37.86%,and it shows good repeatability,low detection limit（200 ppb）and short response recovery time（158 s and 738 s,respectively）.In addition,the sensor has good selectivity for interfering gases such as CO,H₂S,NH₃,ethanol,toluene and xylene.The way to improve the sensitivity of materials by inducing the enrichment of lattice oxygen through hierarchical structure could provide a new idea for the preparation of high-performance gas sensing materials.（2）Cu O/Ni O composites doped with Ti O₂ quantum dots were synthesized under the condition of alternating electromagnetic field.The doping of quantum dots increases the adsorption sites on the surface of the material,which makes the material have good gas sensing characteristics for H₂S gas.Under the optimum operating temperature of 180℃,the response to10 ppm H₂S gas is 57.14%,the lower detection limit is 100 ppb,and it shows good selectivity for H₂S gas.（3）Cu O/Ni O composites derived from MOFs were synthesized by low-temperature precursor hydrothermal method and high-temperature sintering for H₂S detection.The composite has good gas sensing characteristics for H₂S gas at room temperature and low-temperature environment（4℃and-18℃）.Under the optimum operating temperature of 180℃,the response to 50 ppb H₂S gas could reach 106%.At the same time,the composite has high selectivity,its response time and recovery time are 115 s and 251 s respectively,and the lower detection limit is 1 ppb.Low temperature precursor hydrothermal method could obtain more active adsorption sites through the morphology and structure of MOFs derivatives,which has good guiding significance for improving the gas sensing characteristics of materials.（4）By improving the packaging process of the sensor,a planar gas sensor was fabricated on the basis of the synthesized sensitive composites.The sensor was used to detect meat samples（pork and fish）,test and analyze the volatile gas produced in the process of meat deterioration,and study the change of meat freshness with storage time in different environments.In addition,by introducing the signal conditioning circuit,a set of miniaturized and portable meat freshness detection system is constructed,a fast,efficient and nondestructive meat freshness detection scheme based on semiconductor metal oxide gas sensor is designed.