| Raman scattering is a kind of inelastic scattering phenomenon,which generates scattering light,whose photon frequency is different from incident light.The main reason for it is that the frequency of the resulted scattering light is changed by molecules in substance,when the light irradiates onto the surface of substance.The difference of the frequency between incident light and scattering light is called Raman shift.According to the value of Raman shift,the structural information of the substance,including chemical bond and functional group,can be determined.Thus,the Raman spectrum,generated from Raman scattering,is usually used to judge the category of substance.The Raman spectrum of substance has the property of specificity,so it is also called "fingerprint".However,based on the reason of minimal Raman scattering cross section of molecule,the signal of common Raman scattering is pretty weak,which limits its application to some degree.Surface-enhanced Raman scattering(SERS)is the main development of Raman scattering,which mainly depends on the enhancement of scattering light signal by enhancing substrate.Enhancing substrate is commonly made of noble metal,and generally it has rough microstructure on its surface.Usually,the noble metal used to prepare substrate includes gold,silver,platinum and so on.Based on the enhancement of substrate for Raman signal,the signal intensity of substance can be enhanced more than 106 times.Compared with common Raman scattering,SERS overcomes the problem of weak signal intensity,simultaneously it has many advantages,such as rapid response,simple sampling,nondestructive detection and trace analysis.Up to now,SERS spectra technology can be widely used in many fields,including food safety,environment monitoring,chemical analysis and so on.In this article,aimed at the application of SERS spectra technology in food safety,two kinds of noble metal-based SERS substrate were prepared,including Au-based SERS substrate which has three-dimensional structure and Ag-based flexible SERS substrate,and they were applied in the detection of prohibited fish drugs in aquatic products market.By using Rhodamine 6 G(R6G)to study the SERS property of the substrates,the conclusion was confirmed that both the two substrates have excellent enhancement performance of Raman signal.Using the Au-based SERS substrate with three-dimensional structure,the detectable accuracy of R6G can reach the concentration of 10-7 M,and the enhancement factor(EF)was estimated to be 4.03 × 104,indicating the outstanding sensitivity of the substrate.Based on the Ag-based flexible SERS substrate,the determination of R6G can achieve as low as 10-8 M,the EF was calculated to be 3.29 × 105,and the RSD of the peak intensities in 100 SERS spectra was computed to be 8.479%,verifying that the substrate has not only splendid signal sensitivity but also standout uniformity.Meanwhile,on the base of the bending strain cycles and the detection of R6G,the flexible SERS substrate also has good flexibility,which is promising for it in practical application.Based on the Au-based SERS substrate,the detection of two kinds of prohibited fish drugs,involving crystal violet(CV)and malachite green(MG),can reach 10-7 M,and the quantitative logarithmic relation curve was obtained.In addition,the detection result in water for aquatic product matches the linear relation when the substrate is applied in real environment.Applying the Ag-based flexible SERS substrate,the detectable concentration of MG can achieve 10-7 M in both environment including in water for experiment and aquatic product,and the ideal logarithmic linear relation was gained.To further expend the application of the substrate,sampling on the surface of MG-dipped fish was finished,and the result is in consistent with the logarithmic linear relation,which is meaningful for the Ag-based flexible SERS substrate to further develop the practical application in real environment. |
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