| Most of the traditional methods for the detection of harmful substances in food have the disadvantages of high equipment cost,time-consuming and laborious testing,tedious sample preparation,and unsuitability for on-site testing.Surface-enhanced Raman spectroscopy?SERS?is a highly sensitive analysis technique with the advantages of rapid detection and low sample consumption.With the rapid development of laser technology and nanotechnology,SERS has been widely used in food safety,environmental monitoring,biomedicine and other fields.However,in real sample detection,the overlapping of the spectral characteristic peaks of other components in a complex system will bring some difficulties to the accurate analysis of the molecules to be detected,so it is necessary to combine the separation function and the SERS detection function to avoid interference,which achieves the purpose of sensitive detection.At present,the development of a SERS composite substrate that can quickly separate/detect analyte mixtures has become one of the hotspots in SERS technology research.However,most used SERS substrates are hard substrates,which are fragile and not easy to carry,and need to use separation equipment in combination,simultaneously the prepared sol substrate is also unstable.At present,flexible SERS substrates having separation functions usually use cellulose paper as substrates,but there are disadvantages such as complex preparation processes,long analysis time,and unsatisfactory substrate stability.Therefore,the fast preparation of composite substrates with separation/SERS detection capability,their performances?uniformity,stability?,and the application in food safety testing has become the concerns of our research.The specific research contents are as follows:1.We used a method of sputtering gold on filter paper to quickly prepare a uniform and stable paper chromatography combined with SERS?PC-SERS?substrate.First,the separation ability of PC was used to realize the separation of trace bactericides?malachite green,methylene blue and crystal violet?in aquaculture water,and then detected the separated spots by SERS technology,which was proved the separation effect and sensitive detection ability of PC-SERS for mixed systems.The electromagnetic hot spots generated by the gap between the gold nanoislands on the filter paper's fiber to enhance the Raman spectrum signal and improve the detection sensitivity.Therefore,based on Au3 PC-SERS substrate,rapid separation and sensitive detection of fungicide mixtures can be achieved,and it has broad application prospects in the detection of multi-component practical systems.2.Based on the first part of the work,the uniform and stable Au3 PC-SERS substrate was used to separate and detect heavy metal ions(Cd2+,Ni2+and Cu2+)that may present in rice,which expanded the application of this SERS substrate.In this work,we first successfully separated three heavy metal ions on the 4-MBA modified Au3 PC-SERS substrate,and then added 4-MBA@Au NPs to formed the“4-MBA@Au3 PC-SERS substrate/heavy metal ion/4-MBA@Au NPs”sandwich structure,using electromagnetic coupling between metal nanoparticles in the structure to enhance the4-MBA's SERS signal that to achieve the purpose of indirect detecting Raman-inactive heavy metal ions.This method can not only eliminate the interference of multiple components,but also shortens the detection time of commonly used detection methods for heavy metal ions in complex samples.With the help of portable Raman equipment,it can be applied to the field monitoring of food quality.3.The Au3 PC-SERE substrate used in the above two works has shortcomings in the detection of electronegative substances.Therefore,in order to achieve the separation and detection of electronegative substances in the third work,the PEI solution was added to Au NPs to synthesize electropositive PEI@Au,which was adsorbed on filter paper to prepare a PEI@Au PC-SERS substrate.Electronegative pigments?lemon yellow,sunset yellow,and carmine?in carbonated beverages were realized by electrostatic adsorption.At the same time,for antibiotics with small Raman scattering cross-sectional area in milk?tobramycin and gentamicin?,the Schiff base products were generated through the carbonyl groups of amino and p-phthalaldehyde,to increase the Raman cross-sectional area of antibiotics.Results showed that those mixtures can be successfully separated and detected by combining with PC-SERS.Therefore,this method has great significance for the separation/detection applications of electronegative materials and complex systems with small Raman scattering cross-sectional areas. |
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