Bioactive Small Molecules Interacting With The Metal Surface Raman Spectroscopy

The confocal laser Raman microspectroscope has high spatial resolution and sensitivity as well as SERS can provide the information at molecular level. In addition, self-assembled monolayers (SAMs) technique can present a uniform and order molecular array as a well defining mode for surface study. In this thesis, the three methods mentioned above, were employed together to observe the mechanism and phenomenon of surface process. The main contents of this thesis include the following parts: L-alanine is applied widely and the one important amino acid to build up proteins. Based on the results of quantum chemistry calculation and the mechanism of SERS, it suggests that L-alanine acid molecules anchor on the silver surface through carboxyl and nitrogen atoms since the signals were mainly due to the carboxyl and the nitrogen of L-alanine acid.N-acetyl-alanine as an N-acyl amino acid provides multiple possible adsorption ways at the surface. And the monolayers of N-acetyl-alanine at the metallic surface could be served as a biocompatible functional interface to construct biosensors. The Raman and surface-enhanced Raman scattering (SERS) spectra for N-acetyl-alanine self-assembled onto the silver surface were recorded under different pH media. Assignments of the obtained spectra were performed by the density functional theory (DFT) calculations at BLYP/6-311G method. Based on SERS producing mechanism, the adsorption fashions of N-acetyl-alanine at the silver surfaces were deduced that the fully protonated N-acetyl-alanine adsorbed on the silver surface via the imine group together with the carboxylate group, while it anchored onto the surface through not both the imine and the carboxylate groups and also the amide group after completely deprotonated in the basic solution.Sulfanilamides are the first effective chemotherapeutic agents to be employed systemically for the prevention and cure of bacterial infections in humans. Furthermore, sulfa drugs and their complexes have many applications, such as diuretic, antiglaucoma or antiepileptic drugs, among others. After the electrochemically roughened silver surface, SERS spectra of sulfanilamide SAMs on the metal surface were obtained. The electrochemical and in situ spectroelectrochemical methods are used to investigate the relationships of structure-properties and examine the stability of monolayers. The electrode potential was varied between -1.5 and 0 V in steps of 0.1 V. According to the obtained SERS spectra, it is found that, the changes of the peaks are almost related to the vibrational modes of the benzene ring. With the potential moved more negative, the molecule is much closer to the silver surface. As the potential shifting to further negative values, the molecule became away from the silver surface and detached from the silver surface at -1.5 V.