【作者】 沈佳彬；

【导师】 朱永恒；

【作者基本信息】 上海海洋大学 ， 食品工程， 2022， 硕士

【摘要】 海鲜鱼类富含微量氨基酸和不饱和脂肪酸,有利于增强人体免疫系统、维持生命代谢途径以及预防神经疾病。随着人民群众对于高质量生活水平的追求,市场对于高品质海鲜鱼类的需求量正日益增加。但是,变质海鲜不仅失去了其原有的营养价值,还会因食材腐败变质、致病菌增生等情况引起发烧、头晕、腹泻等症状,严重危害人们的健康。近年来,食用变质过期海鲜造成的食品安全事件影响恶劣,大大降低了品牌的大众信誉,严重危害了人民群众的生命安全。因此,判断海鲜鱼类的新鲜度和质量对于确保食品安全是至关重要的。三甲胺(TMA)作为氧化三甲胺降解的产物,是传统致癌物(亚硝基胺)的前体物质,也是海鲜鱼类腐败的特征性气体之一。因此,建立现场、准确、无损的检测海鲜鱼类TMA含量食品安全技术对于人们评估海鲜鱼类的质量品质以及保护人们身体健康具有重要意义。基于金属氧化物半导体材料的气体传感器因其易于制造、灵敏度高等优点在检测微量挥发性有机化合物的领域中备受关注。其中,氧化铁材料作为一种环境友好,自身稳定的n型半导体(Eg=2.1 e V),因其具有独特的物理化学性质而广泛应用于多种领域,包括气体传感器。但是,纯氧化铁作为气敏材料存在自身电阻高、工作温度高等缺点,优化材料的形貌和结构可以提高传感器响应性能。本论文通过控制氧化铁材料形貌、掺杂增敏剂和复合其他金属氧化物材料制备出了形貌结构多样、双金属纳米颗粒修饰和复合二氧化锡(Sn O2)的氧化铁(Fe2O3)纳米材料,并进一步研究了上述的气敏材料对于三甲胺气体敏感特性的影响,讨论了相应的气敏机理以及不同优化方式带来的相关增敏机理,最后将制备的气体传感器应用于鱼类实际样品的新鲜度检测中,以期为现场快速、便携、无损检测海鲜鱼类新鲜度提供坚实的理论依据和新的检测方法。本论文的主要研究如下:1、基于不同形貌Fe2O3立方体的制备及其在鲫鱼新鲜度检测中的应用。本章利用水热法合成布鲁斯蓝,通过控制离子交换反应时间,制备出实心、核壳和中空立方体形貌的Fe2O3。中空立方体展现出最佳的三甲胺气敏性能,基于该材料的传感器在最佳工作温度(230°C)下,对200 ppm三甲胺的响应为6.3,响应恢复时间分别为14/91 s。此外,基于Fe2O3中空立方体的传感器对鲫鱼在常温储存条件下的新鲜度变化进行测试,并基于以上结果为接下来的实验提供参考。最后,本章讨论了以上三种气敏材料对三甲胺气体的传感机理。2、基于Au@Pt/Fe2O3中空立方体的气体传感器快速高效检测大黄鱼中的三甲胺含量。基于第二章的Fe2O3中空立方体材料,通过油胺还原法合成Au@Pt双金属颗粒,再利用浸渍超声处理合成Au@Pt合金掺杂量分别为0.5 wt%、1.0 wt%、1.5wt%、2.0 wt%和4.0 wt%的Au@Pt/Fe2O3纳米中空立方体材料,同时也制备了单金属修饰的Au/Fe2O3和Pt/Fe2O3纳米材料用于比较研究。从气敏测试结果可知,Au@Pt合金可以显著提高Fe2O3纳米中空立方体对三甲胺的气敏性能。气敏性能增强的主要原因可能是由于材料的中空结构提供了更多的活性位点,同时Au、Pt金属元素的化学增敏作用以及双金属Au@Pt的协同增敏作用。其中,基于1.0 wt%Au@Pt/Fe2O3中空立方体材料的传感器在最佳工作温度150°C下表现出优秀的气敏性能,对100 ppm三甲胺的响应高达32,响应时间缩短为5 s,对低浓度1 ppm三甲胺也具有较好的响应(Ra/Rg=2.1)。此外,使用Au@Pt/Fe2O3传感器对大黄鱼在不同储存时间、储存温度下的新鲜度进行测试,测试结果经气相色谱-质谱联用技术进行验证,提高了该气体传感器应用于实际样品的检测的可能性。最后,对Au@Pt/Fe2O3纳米中空立方体气敏材料对三甲胺测试的传感机理进行了深入的讨论和分析。3、基于Au@Pd/Fe2O3-Sn O2中空复合立方体的气体传感器快速高效检测石斑鱼中的三甲胺含量。本章同第二章利用水热法合成布鲁斯蓝,在锡酸钾溶液环境中进行离子交换反应,制备出中空立方体结构的Fe2O3-Sn O2复合材料;然后通过原位还原法合成Au@Pd合金掺杂浓度分别为0.5 wt%、1.0 wt%、1.5 wt%、2.0 wt%的Au@Pd/Fe2O3-Sn O2中空复合立方体材料,同时也制备了纯Fe2O3、纯Sn O2、Fe2O3-Sn O2、Au/Fe2O3-Sn O2和Pd/Fe2O3-Sn O2纳米中空立方体材料用于比较研究。根据气敏测试结果,Au@Pd/Fe2O3-Sn O2复合材料可以显著提高Fe2O3立方体对三甲胺的气敏性能,这可能归功于Fe2O3和Sn O2表面形成的n-n异质结结构和Au、Pd金属元素的增敏作用以及双金属Au@Pd的协同增敏作用。其中,基于1.5 wt%Au@Pd/Fe2O3-Sn O2中空复合立方体材料的传感器在最佳工作温度210°C下表现出优秀的气敏性能,对100 ppm三甲胺的响应为72,响应恢复时间为4/59 s,对低浓度1 ppm三甲胺也具有较好的响应(响应值为3.1),检测限低至0.5 ppm。此外,Au@Pd/Fe2O3-Sn O2中空复合立方体传感器对石斑鱼在不同储存时间、储存温度下的新鲜度进行测试,测试结果经气相色谱-质谱联用技术进行验证。最后,Au@Pd/Fe2O3-Sn O2纳米中空复合立方体气敏材料对三甲胺测试的传感机理也进行了深入的讨论和分析。更多还原

【Abstract】 Seafood fish is rich in trace amino acids and unsaturated fatty acids,which are beneficial for strengthening the human immune system,maintaining the metabolic pathways of life and preventing neurological diseases.With the people’s pursuit of high-quality living standards,the demand for seafood and fish in China’s market and even the global market is increasing.However,spoiled seafood not only loses its original nutritional value,but also causes fever,dizziness,diarrhea and other symptoms due to spoilage of ingredients and proliferation of pathogenic bacteria,which seriously endangers people’s health.In recent years,the consumption of spoiled and expired seafood caused by food safety incidents have a bad impact,greatly reducing the public reputation of the brand and seriously endangering the lives of the people.Therefore,judging the freshness and quality of seafood fish is essential to ensure food safety.Trimethylamine（TMA）,as a product of oxidized trimethylamine degradation,is a precursor substance of the traditional carcinogen（nitrosamines）and one of the characteristic gases of seafood fish spoilage.Therefore,the establishment of on-site,accurate and nondestructive food safety techniques for the detection of TMA content in seafood fish is important for people to assess the quality of seafood fish and to protect their health.Gas sensors based on metal oxide semiconductor materials have attracted much attention in the field of detection of trace volatile organic compounds due to their ease of fabrication and high sensitivity.Among them,iron oxide material（Fe₂O₃）,as an environmentally friendly and self-stable n-type semiconductor（E_g=2.1 e V）,is widely used in various fields,including gas sensors,because of its unique physicochemical properties.However,pure Fe₂O₃as a gas-sensitive material has the disadvantages of high self-resistance and high operating temperature,and optimizing the morphology and structure of the material can improve the sensor response performance.In this paper,Fe₂O₃nanomaterials with various morphological structures,bimetallic nanoparticle modification and tin dioxide（Sn O₂）compound were prepared by controlling the morphology of Fe₂O₃,doping sensitizers and compounding other metal oxide materials,and further investigated the effects of the above gas-sensitive materials on the sensitive properties of TMA gas,and discussed the corresponding gas-sensitive mechanisms and the related sensitization mechanisms brought by different optimization methods.The corresponding gas-sensitive mechanisms brought by different optimization methods were discussed,and finally the prepared gas sensors were applied to the freshness detection of actual fish samples,in order to provide a solid theoretical basis and a new detection method for the rapid,portable and nondestructive detection of seafood fish freshness in the field.The main research of this paper is as follows:1.Preparation of Fe₂O₃nanocubes（NCs）based on different morphologies and their application in the freshness detection of Carassius auratus.In this chapter,Fe₂O₃with solid,nucleoshell and hollow cube morphology was prepared by controlled ion exchange reaction time using hydrothermal synthesis of Bruce blue.The hollow cube exhibited the best gas-sensitive performance for TMA,and the response of the sensor based on this material was 6.3 for 200 ppm TMA at the optimum operating temperature（230℃）with response recovery times of 14/91 s.In addition,the Fe₂O₃hollow cube based sensor was tested for the freshness variation of Carassius auratus under ambient storage conditions and based on the above results for the next experiments.Finally,this chapter discusses the sensing mechanism of the above three gas-sensitive materials for TMA gas.2.Bimetallic Au@Pt nanocrystal sensitization mesoporous Fe₂O₃hollow nanocubes for highly sensitive and rapid detection of pseudosciaena crocea freshness at low temperature.Based on the Fe₂O₃hollow NCs material in Chapter 2,it was synthesized Au@Pt bimetallic particles by oil amine reduction and ultrasonic impregnation method,the Au@Pt alloy modification concentrations were 0.5 wt%,1.0 wt%,1.5 wt%,2.0 wt%and 4.0 wt%,respectively.Au/Fe₂O₃and Pt/Fe₂O₃NCs materials were also prepared for comparative study.According to the gas sensing test results,The Au@Pt alloy can significantly improve the gas sensing performance of Fe₂O₃hollow NCs to TMA.The main reason for the enhancement of gas sensing performance may be that the hollow structure of the material provides more active sites,the chemical sensitization of Au and Pt metal elements and bimetallic Au@Pt synergy.Of which,1.0 wt%Au@Pt/Fe₂O₃hollow NCs material shows excellent gas sensing performance at the optimal working temperature of 150℃.The response to 100 ppm TMA is as high as 32,and the response time is shortened to 5s.It also has a good response to low concentration of 1 ppm TMA（response value is 2.1）.In addition,the freshness of pseudosciaena crocea was tested by Au@Pt/Fe₂O₃sensor under different storage time and storage temperature.The test results were verified by gas chromatography-mass spectrometry（GC-MS）,which provides a great possibility for the application of gas sensor in the detection of actual samples.Lastly,the sensing mechanism of Au@Pt/Fe₂O₃hollow NCs gas sensing material for trimethylamine test is also deeply discussed and analyzed.3.Bimetallic Au@Pd nanocrystal sensitization mesoporous Fe₂O₃-Sn O₂hollow nanocubes for highly sensitive and rapid detection of grouper freshness.In this chapter,Bruce blue was synthesized by hydrothermal method,and Fe₂O₃-Sn O₂nanocomposites with hollow cubic structure were prepared by full ion exchange reaction in potassium stannate solution;Then it was synthesized by in-situ reduction Au@Pd.The alloy modification concentrations were 0.5 wt%,1.0 wt%,1.5wt%and 2.0 wt%Au@Pd,respectively.At the same time,pure Fe₂O₃,pure Sn O₂,Fe₂O₃-Sn O₂,Au/Fe₂O₃-Sn O₂and Pd/Fe₂O₃-Sn O₂hollow NCs materials were also prepared for comparative study.According to the gas sensing test results,the Au@Pd/Fe₂O₃-Sn O₂composite can improve the gas sensing performance of Fe₂O₃NCs to TMA,which may be due to the n-n heterojunction structure formed on the surface of Fe₂O₃and Sn O₂,the sensitization of Au and Pd metal elements and bimetallic metals Au@Pd synergy.Of which,1.5 wt%Au@Pd/Fe₂O₃-Sn O₂hollow NCs material shows excellent gas sensing performance at the optimal working temperature of 210℃.The response to 100 ppm TMA is 72,the response recovery time is 4/59s,it also has a good response to low concentration of 1 ppm TMA（response value is 3.1）,and the detection limit is as low as 0.5 ppm.In addition,the freshness of grouper under different storage time and storage temperature was tested by Au@Pd/Fe₂O₃-Sn O₂sensor,and the test results were verified by gas chromatography-mass spectrometry（GC-MS）.Finally,the sensing mechanism of Au@Pd/Fe₂O₃-Sn O₂material for TMA test is also deeply discussed and analyzed.更多还原