Preparation Of Magnetic SERS Substrate And Application In The Field Of Fast Detection For Food

The traditional analysis techniques of laboratory such as chromatography mass spectrometry,which aiming at the multi component complex system for qualitative,quantitative analysis.But long analytical period,lag analysis results,make it can not timely and effectively monitoring the status of food safety and environment.Therefore,seeking a fast,efficient and accurate food analysis method is a knotty problem in the field of food rapid detection.Surface-enhanced Raman Scattering?SERS?is a fingerprint identification technology based on scattering theory.Comparison with other testing techniques,it owns the characteristic of less sample consumption,fast testing speed,fingerprint property,and high sensitivity etc.This technology is used for ultrasensitive detection of trace substances in solvent system,especially qualitative test on-site has attracted more attention by large amount of researchers.To develop a simple and effective pretreatment method combine with SERS detection technology is the urgent analysis method in the field of fast food inspection.Magnetic material will be used to develop a high selectivity,environment friendly sample pretreatment method based on SERS technology in this study.Combination this sample pretreatment method with miniaturization of Raman spectrometer effectively,it will provide new technical means for the development of fast and efficient food testing and monitoring technology,and then escorting for the food safety.The research mainly includes the following three aspects:?1?The combination of efficient sample pretreatment and detection technology is the premise of developing rapid detection method.In order to simplify the pre-processing steps and shorten the pretreatment time,a multifunctional SERS activity substrate of magnetic graphene?Fe₃O₄@GO@Ag?is fabricated successfully via layer-by-layer assembly of silver and graphene oxide?GO?nanoparticles?NPs?on the magnetic ferroferric oxide particles.This ternary particle possesses the functions of magnetic property,SERS activity and adsorption ability simultaneously.Based on the advantages of graphene oxide,combined solid phase extraction with SERS technique for pesticide residue detection on the surface of peel and vegetables.We put forward a new method called surface magnetic solid-phase extraction?SMSPE?technique.SMSPE integrates many sample pretreatment procedures,such as analyte extraction,separation and detection,all-in-one.Combination SERS activity ternary particle of Fe₃O₄@GO@Ag and the technology of SMSPE,can realize the pesticide residue detection and the whole detection process will be finished within 20 min.?2?The ternary composite material of Fe₃O₄@GO@Ag has multi-functions of analyte extraction,enrichment,separation and detection,all-in-one.However,the ternary SERS substrate prepared via fractional step method has many limitations,for example: complex preparation process,long preparation time,high requirement on the preparation parameters.Based on the above,it is not suitable for large scale production.So we try to prepare ternary SERS substrate by one-pot method: with acetylacetone iron as a source of iron,ethylene glycol as solvent,NaAc as the reducing agent,polyethyleneimine?PEI?for electrostatic assembly agent.The effect of NaAc and AgNO₃ dosage on Fe₃O₄ and AgNPs loading on the surface of the grapheme are investigated,respectively.The experiment of technical amplification is designed in accordance with the optimizing experimental ratio.The SERS activity study of ternary SERS substrate,which prepared by one-pot method is completed.The results showed that the applied effect of ternary SERS substrate fabricated by the method of one-pot is better than fractional step.?3?Illegal cooking oil discrimination is a puzzle in the field of analytical chemistry and food safety,capsaicin is the important target molecular used to identify illegal cooking oil,the detection technology of capsaicin mainly implementation by high performance liquid chromatography-mass spectrometry?HPLC-MS?at present.This thesis based on the technology of surface enhanced resonance Raman scattering?SERRS?,using molecular derivatization,has established ultrasensitive detection methods of the exogenous target molecules: capsaicin and dihydrogen capsaicin in the cooking oil.By using special derivatization reagent,starting from the producing conditions of SERRS,which is devoted to making the maximum overlap between the maximum absorption wavelength of target molecules and excitation wavelength of composite material.Magnetic nanoparticles with magnetic aggregation function is used as SERS substrate,the ultrasensitive detection of capsaicin and dihydro-capsaicin will be realized by resonance Raman Scattering-surface enhanced Raman scattering?Surface-Enhanced Resonance Raman Scattering,SERRS?,the detection limit can reach 1.0×10-9 M.The method of SERRS provides a simple,rapid and ultrasensitive analysis method in identification cooking oil.