Applications Of Multiplicative Effects Model To Quantitative Surface-Enhanced Raman Spectroscopy

Surface-Enhanced Raman spectroscopy(SERS) has great application potential in various fields because of its advantages of simple sample pre-treatment, excellent molecular specificity, and exquisite sensitivity, etc. However, the molecule of interest must be adsorbed onto a suitable roughened metal surface of substrate to achieve SERS signals. The SERS signal of analyte molecules depends on not only the analyte concentration but also the physical property of enhancing substrate, the intensity and alignment/focusing of laser excitation source. Therefore, the relationship between the SERS signal of a sample and the concentration of the target chemical species in the sample does not follow the commonly used linear model. The rather complexed relationship between the SERS signals and the concentration of the target chemical species renders the SERS technique to be a qualitative or semi-quantitative technique.Recently, Chen, et al. proposed an advanced mulplicative effects model for quantitative surface-enhanced Raman spectroscopy(MEMSERS). The MEMSERS model provides a theoretical basis for the development of quantitative SERS techniques for complex systems. This thesis has attemped to combine SERS technique with MEMSERS model to achieve accuate quantitative SERS analysis for several complex systems. The main contents are as follows:In Chapter 2, With Au nanoparticles as SERS enhancing substrate and p-thiocresol as internal standard, accurate quantitative analysis of captopril in tablet and blood plasma samples was achieved by surface-enhanced Raman spectroscopy in combination with the multiplicative effects model. The values of limit of detection and limit of quantification were 0.149 and 0.451 ?M, respectively. The recovery rates were in the range of 94.3% to 109.8%, which were comparable to the results of LC-MS/MS. These experimental results fully demonstrated the practical applicability of the MEMSERS model in quantitative SERS analysis of complex syatems.In Chapter 3, When reacting with H+, the molecular structure of4-mercaptopyridine(4-MPY) shows significant changes, which results in perceptible changes in its SERS spectrum. Based on the above characteristic of 4-MPY and the MEMSERS model, a generalized ratiometric indictor based SERS technique was developed, and successfully applied to the detection of p H value of an analog cellular system.In Chapter 4, Methylene blue and alizarin red can be strongly absorbed onto the surface of graphene oxide(GO). Moreover, the SERS spectrum of Graphene possesses two disctinct and relatively stronge peaks at 1336 and 1598 cm-1, respectively, which can serve as internal standards in quantitative SERS assays. With GO/Ag composite nanoparticles as SERS enhancing substrates, the quantitative analysis of methylene blue and alizarin red was realized by the combination of SERS technique with the MEMSERS model.