Construction Of Core-Shell SERS Material And Its Application In The Detection Of Pesticides And Explosives

The development of agricultural industrialization makes the production of agricultural products more and more dependent on exogenous substances such as pesticides.Trinitrotoluene(TNT)has become one of the most commonly used dangerous explosives due to its military purpose and increasingly rampant terrorist activities.The loss of these substances in the soil,water and air will cause human disease,abnormal development,and even indirectly lead to poisoning and death.Therefore,it is urgent to establish a rapid detection technology for a large number of pesticides and TNT residues in water and environment.What's more,it is more and more necessary to monitor these substances quickly and accurately,which promotes the construction of portable analysis platform.Surface enhanced Raman spectroscopy(SERS)is a super sensitive,rapid and universal analytical tool,which can detect samples without complex pretreatment process and comprehensive fingerprint information.It has a wide application prospect in environmental monitoring,biomedicine,food safety and other fields.Nano materials are usually used as SERS reinforcement substrates,and their properties,surface morphology and self structure have some influence on the reinforcement effect.In the practical application of SERS detection,one of the main obstacles is the lack of an efficient and flexible method for reproducible large-scale preparation of high stability SERS substrate.With the rapid development of modern nanotechnology,it is possible to synthesize SERS substrates with high sensitivity and repeatability on a large scale.At the same time,the combination of SERS detection technology and other traditional detection methods,as a multi-sensor detection system,can improve the sensitivity of detection,reduce the detection limit,and provide greater possibility for rapid and sensitive detection of substances.Therefore,it is of great theoretical value and practical significance to construct a new SERS substrate for rapid screening and detection of pesticide residues in seawater,as well as for rapid and sensitive detection of TNT residues by multi-sensor method.In the first chapter,the introduction part introduces the background of the subject,the significance of theoretical and practical research,the reinforcement mechanism and substrate preparation of SERS,as well as the key application fields of SERS.In the second chapter,a SERS analysis technique based on electrostatic self-assembly gel array was developed.First,the silver coated polyvinyl alcohol gel microspheres were prepared by microfluidics technology(PVA-Ag).Microgels)and a clever "Elven" SERS sensor was designed by ingeniously using electrostatic adsorption.Under the presence of charged pesticide molecules,electrostatic bonding between pesticide molecules and oppositely charged PVA-Ag Gel Microspheres occurred,and interfacial emulsification was used to realize the directional adsorption and aggregation of pesticide molecules on the surface of microspheres.This method,on the one hand,uses the electrostatic effect to assemble in situ the ordered array structure of gel microspheres.On the other hand,it can concentrate trace or trace pesticide molecules into the gap of high-density microsphere array and obtain highly sensitive and high specific SERS signals.The liquid liquid interface SERS technology can not only achieve in situ efficient enrichment and rapid screening of pesticide molecules,but also improve the sensitivity of analysis and detection,and also construct a self-assembled gel ordered array structure based on electrostatic induction,which improves the stability and repeatability of the analysis results,and makes up for the shortcomings of the traditional SERS substrate.It is worth noting that the liquid-liquid interface SERS technology can realize the on-site rapid screening and analysis of pesticide molecules in single-phase or multi-phase systems.The method can realize the on-site rapid detection of pesticide molecules without additional pretreatment devices and complex analysis steps.PVA-Ag gel microspheres have stable and ordered surface morphology and nanostructure,and can be used for batch production and continuous detection.The results show that the method has good reproducibility and reliability,so it shows great potential in the field of environmental pollutants in situ analysis and point-of-care detection.In the third chapter,a fast and sensitive TNT detection method based on colorimetric fluorescence SERS triple sensing mode is developed.In our study,cysteine was used as the stabilizer of gold nanoparticles.Cysteine was added to the newly prepared gold nanoparticles,and the surface of the gold nanoparticles was modified by cysteine by Au-S covalent bond.Addition of cysteine did not change the color and absorption spectrum of gold nanoparticles.At the same time,adding mercaptopropionic acid to Cd Se / Zn S QDs will not change the fluorescent color of QDs.When the gold nanoparticles modified with cysteine were mixed with the quantum dots modified with mercaptopropionic acid,the fluorescence quenching occurred.When TNT liquid is added to the mixture,TNT will react with cysteine to form meisenheimer complex.Meisenheimer complex is a ?-complex formed by covalent addition of nucleophilic molecules and electron deficient aromatic substrates.The color of TNT solution turns red,indicating the formation of meisenheimer complex.The formation of meisenheimer complex can also be detected by SERS.At the same time,the fluorescence recovery of the mixed solution is the principle of three sensor detection of TNT.Therefore,the new multi-sensor detection method constructed in this study can selectively detect TNT,and has low detection limit and high sensitivity,which has potential application value in food safety and environmental detection.