Preparation Of Core-shell SERS Substrates And Their Application In Detection Contraband Pigments In Food

With the widely use of the synthetic pigments in the food industry, food safety incidentscaused by adding pigments illegally in food occur repeatedly. So rapid detection of pigmentsin food gradually been in a hot research.Because of the excellent performance in Surfaceenhanced raman scattering (SERS), core-shell nanoparticles are often used as SERS activesubstate. And this SERS technology with core-shell nanoparticles is sensitive, convenience,fast and undamaged, which has been applied to the field of biomedicine, catalysis science,environmental protection broadly. Furthermore, the application of this technology is graduallyincreasing in food safety. In this study, this technology is used to detect the common yellowand blue pigments which are always used illegally and the methods are established for rapidscreening of basic orange II, acid orange II and brilliant blue, respectively.First of all，the two substrates was prepared and the SERS effect of the two subsrates wasoptimized.The SiO2@Au core-shell nanoparticles was synthesized using the method ofSt ber and seed growth method. Three different shell thickness of the Au shell on thesubstrates was studied to obtain better SERS effect.50nm Au nanoshells was acquired and itwas proved to have the best SERS effect. In order to enrich the SERS substrates, expand theapplication of SERS technology and optimize the experimental steps, we synthesized themagnetic Fe3O4@Au core-shell nanoparticles and good magnetic was used for the rapidseparation and dispersion in the preparation process. Three kinds of substrate prepared bydifferent reducing agent was studied to get better SERS effect. The Fe3O4@Au core-shellnanoparticles prepared by formaldehyde performed the best SERS effect.Secondly, the SERS effect of the two substrates was studied and five pigments weredetected by SERS method with the two substrates. And the detection conditions wereoptimized. It was found that the SiO2@Au was suitable for detection basic orange II and theFe3O4@Au was suitable for detection acid orange II and brilliant blue. Then, Thecharacteristic peaks of the three pigments molecules were assigned according to thecomparison of the theoretical raman vibrations and the experimental raman vibrations. Thecharacteristic peaks of basic orange II was997,1171cm-1, the characteristic peaks of acidorange and blue respectively990,1620and1160,1612cm-1. What’s more, the testing systemcomposed by the SERS substrate and pigments were optimized respectively. Methods wereestablished to detect three kinds of pigments based on the two substrates. The detection limitof basic orange II, acid orange and blue were0.1,1and0.5μ g/ml, respectively.Finally, the three pigments in food samples were detected by SERS method. Accordingto the characteristic peaks of brilliant blue, the brilliant blue was found in wine. The pigmentsin the other food were extracted by adding standard pigments which were mixed inaccordance with the real food samples. And the results of SERS verified by HPLC-UVmethod, showed the SERS method can be used for qualitative detection of basic orange II,acid orange II, brilliant blue, and it is expected to be used for rapid screening of prohibitedpigments in food.