| The report of the 19 th National Congress of the Communist Party of China has clearly put forward “implementing the strategy of food safety so that the people can eat safely”.Although some laboratory detection technologies can meet the requirements of precise detection,the sample pretreatment procedure is complex and time-consuming,which makes it difficult to monitor the food safety status in time.Rapid detection technology can make up for its shortcomings,and gradually become a pop technology of food safety detection and inspection.Surface enhanced Raman spectroscopy(SERS)is a new rapid detection method.Its spectral band is narrow and it is not easy to overlap.It can provide the information of material composition and molecular structure.However,the detection system is limited.On the one hand,SERS active nanostructures are usually fixed on the surface of solid substrate,and the hot spot structure is fixed.On the other hand,it is difficult to quantify the SERS signal.And many tests need to be carried out in a suitable liquid system or solid/liquid interface.Therefore,in this paper,the general strategy for the preparation of liquid-interfacial enhanced Raman detection platform(LERP)is first obtained.Then,the relationship between the controllability of self-healing nanoarray structure and the sensitivity of SERS on the LERP is explored,to provide theoretical basis and experimental data support for optimizing the LERP.Through the calibration of solvents,we have obtained statistically significant SERS signals and realized quantitative SERS detection.By using organic reagents as extractants,we have achieved rapid separation and detection of sample components in food.Based on this,the method system of in-situ real-time tracking of molecular reaction process by LERP is preliminarily explored.Inspired by enzyme labeling instrument,we have combine LERP with microporous accessory or microfluidic technology to promote the development of SERS to multi-channel quantitative technology.This technology is as simple and sensitive as enzyme labeling instrument or spectrophotometer,which provides a new way for the detection of food hazards.The results are as follows:1.Aiming at the bottleneck of traditional solid/gas interface or sol particle SERS detection method,the self-assembly of GNPs on liquid/liquid interface(LLI)was designed,and the LERP with superior SERS performance was successfully constructed.By controlling the dynamic tunable and self-healing characteristics of the nanoarrays,the LERP was optimized.Using the characteristic peak of organic reagent as IS,the ability of continuous IS to correct the fluctuation of SERS signal caused by nanoparticle sols,temperature,excitation volume,laser focusing and sample microenvironment was investigated.The platform can be used not only for multicomponent detection,but also for multiphase in-situ detection,and successfully applied to the detection of trace pollutant malachite green(MG)in fish meat.The detection limit(LOD)was 20 n M.2.Generally speaking,only analytes close to the surface of nanoparticles can be detected effectively in SERS.Therefore,how to make nonadsorptive molecules close to the surface is always a key scientific problem in SERS analysis.The organic(O)phase in the LERP provides a hydrophobic environment for nonadsorptive molecules,such as polycyclic aromatic hydrocarbons(PAHs),close to the interfacial plasmonic nanoarrays,to achieve their trace detection.Finite difference time domain(FDTD)simulation shows that the LERP has dualphase accessible asymmetric hotspots,and the electromagnetic field enhancement of chloroform(CHCl3)phase is about four times that of water(W)phase.We speculated that the enhanced electromagnetic field and hydrophobic environment provided by CHCl3 are two important factors for the successful detection of four PAHs.In addition,we also explored the competitive SERS signal changes of adsorptive and adsorptive molecules,adsorptive and nonadsorptive molecules,nonadsorptive and nonadsorptive molecules on the liquid-interfacial enhanced Raman detection platform.The LERP has successfully realized the detection of a variety of PAHs in edible oil,and their LOD were 10 ppb.3.The LERP can be stable in p H=1-14,so it has potential application in monitoring chemical reaction process.The classical molecular reaction,the photocatalytic oxidation of 4-Nitrothiophenol(PNTP)and 4-Aminothiophenol(PATP)by sodium borohydride(Na BH4)were selected to evaluate the monitoring effect of the LERP on the chemical reaction process.The results showed that when p H=1-4,PNTP was directly reduced to PATP.When p H=5-8,PNTP was reduced to DMAB and then to PATP.When p H=9-14,DMAB and PATP coexist all the time.At this time,when Na BH4 is stopped and the interfacial plasmonic nanoarray are continuously irradiated by laser,PATP can be converted into DMAB.Among them,the selfhealing property of the platform ensures the full mixing of various reactants and improves the reaction efficiency.In addition,GNPs with larger particle size was successfully used as catalyst for the first time.This is the first time to study the effect of different p H values on the reduction of PNTP by Na BH4 using the interfacial plasmonic nanoarray,which provides a new idea for tracking the molecular reaction process in food in real time.4.In order to further improve the detection flux of samples,we developed a new on-line plasmonic capsule microfluidic(PCM)technology by combining the LERP with microfluidic technology(PCM-LERP).The excellent water in oil(O/W)characteristics of plasmonic capsule ensure less surface pollution of internal channel and avoid cross contamination between different capsules.Five analytes in different capsules can be detected continuously in one minute,while the detection of dual-analyte and triple-analyte in one capsule shows excellent sensitivity even when the concentration of analyte is two orders of magnitude different.In recent years,new drugs such as hemp chocolate,hemp pastry,hemp candy,jelly,fairy water,fashionable drinks and other food and beverage are emerging,which pose a serious threat to public security and human health.Taking methamphetamine(MA)as an example,the organic phase(CHCl3)was used as the extractant to realize the effective separation and enrichment of MA.Using PCA algorithm,the platform can easily realize the automatic classification of trace MA,and its concentration can be reduced to ppm level.PCM combines with portable Raman devices to realize the fast analysis of multi sample,multi-channel and high-throughput target molecules in complex media.5.Combining LERP with microporous accessories,a simple but more sensitive multichannel quantitative measurement technology is designed(M-A-LERP).The interfacial plasmonic nanoarrays can be stored in a hydrophilic container and in the state of O/W,such as quartz microporous accessory.Instead,it can be stored in a hydrophobic container and in a water in oil(W/O)state,such as a polystyrene(PS)microporous accessory.The results show that the interfacial plasmonic nanoarray has good stability and environmental protection in the quartz microporous accessory.When the laser incident from the bottom of the quartz microplate,the fluctuation of the interfacial plasmonic nanoarray is avoided and the SERS performance is superior.The system can provide 12 samples of high-speed and high-throughput analysis in less than 10 minutes,and has excellent signal reproducibility.Our system shows high-resolution dual and triple analyte detection,which fully retains the signal and Raman characteristics of a single analyte in the mixture.At the same time,the microporous accessory isolated interfacial plasmonic nanoarray prevents contamination between each other and allows accurate quantification of samples.At last,thiram(TAM)was tested.The LOD of TAM was 10 ppb and 100 ppb on apple peel and orange peel,respectively.This provides a great possibility for onsite sensing and a new way for high-performance analysis of SERS. |
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