Quantitative Surface-enhanced Raman Spectroscopy Based On The Combination Of Magnetic Nanoparticles With An Advanced Calibration Model

Surface-Enhanced Raman spectroscopy (SERS) is one of the most powerful andpopular analytical techniques with single-molecule sensitivity, and therefore has greatpotential for application in various fields. However, the molecule of interest must beadsorbed onto the roughened surface of a suitable metallic substrate to achieve SERS.Therefore, the SERS effect relies heavily on the preparation of enhancing substrates.The difficulty in producing highly stable and reproducible SERS enhancing substratesrenders SERS remain a qualitative or semi-quantitative detection technique at thepresent stage. Because of their intrisic limitations and the strict requirements for thesystems under study, traditional chemometrics multivariate calibration models can’teffectively eliminate the detrimental effects caused by the variation in the physicalproperties of enhancing substrates on quantitative SERS assays. In this paper,magnetic nanoparticles combined with the advanced chemometricmethod-multiplicative effects model have been employed to mitigate the detrimentaleffects caused by the variation in the physical properties of enhancing substrates, andhence to realize accurate quantitativeSERS assays.The main work is as follows:In Chapter2, Magnetic nanoparticles (Fe3O4@Au, Fe3O4@Ag) were synthesizedby reducing HAuCl4and AgNO3on the surfaces of Fe3O4nanoparticles according toprevious reported methods with some modifications. The core-shell structures of theferromagnetic composites nanoparticles were characterized in detail by TEM, SERSand UV-vis spectroscopies.In Chapter3, Fe3O4/Au magnetic nanoparticles were combined withmultiplicative effects model to improve the accuracy and precision of quantitativeSERS assays for R6G and methyl green based on the internal standard (p-thiocresolsolution) tagging detection mode. In multiplicative effects model, a multiplicativeparameter was introduced to account for the effects caused by the heterogeneity ofmagnetic nanoparticles on SERS signals and hence realize accurate quantitativeSERSassays.In Chapter4, Multiplicative effects model incorporated with Fe3O4/Agnanoparticles modified by p-thiophenol was used in quantitative SERS analysis ofthiram in water. Experimental results demonstrated that multiplicative effects modelperformed much better than many conventional calibration models for the quantification of thiram in sanmples prepared using both ultrapure water andreal-world environmental water. Compared with previously reported methods for thedetection of thiram, the proposed method has the advantages of simplicity, sensitivityand high accuracy.