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Surface-Enhanced Raman Scattering Research On Self-Assembled Monolayers At The Metal Electrodes

Posted on:2007-05-31Degree:MasterType:Thesis
Country:ChinaCandidate:H ChuFull Text:PDF
GTID:2121360185965276Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
Organised molecular assembly has become one of the most important areas of modern chemical research. Of the variety of approaches used for the formation of organized molecular assemblies, the self assembly is the one foremost important technique. The versatility of self assembled monolayer (SAM) methodology to make functional monolayers on metal surfaces has attracted considerable attention in the recent years, which can improve potential application of such layers in corrosion protection, friction, optics, microelectronics, and chemical sensors.The extension of application of SAMs calls for the deeper understanding of SAMs which requires the analytical methods with the higher sensitivity. Surface enhanced Raman spectroscopy, which has been proved to be one of the most sensitive tools to investigate SAMs, can provide more detailed information on the physicochemical property of SAMs while combined with Raman mapping technique. Based on the spectral feature along with the calculated results from quantum chemistry, we can deduce the orientation of the adsorbed molecule on metal surface. And the stability of SAMs also has been examined by in situ spectroelectrochemical methods. Furthermore, the density functional theory (DFT) presented in the thesis provides the fundamental understanding of the chemisorption of the molecules on gold and silver surface and the structure of the monlayers thus formed. The main contents in the thesis are presented as follows:(1) A combined protocol of the SERS technique with DFT calculation has been used to look into the SAMs of 6-mercaptopurine on silver surface. And it was found that the adsorption mode of 6MP SAMs changed with the pH value of the environment. 6MP was adsorbed on the silver electrode with a tilted orientation via S, N1, and N7 atoms in acid medium, while the SAMs adopted head-on adsorption modes with the S atom and the N1 atom anchoring the silver surface in alkaline medium. However, 6MP SAMs turns to the same upright orientation on the electrode through the S and N7 atoms when either acid or basic solution was removed. The results reveal the desorption potentials of 6MP SAMs under acid and alkaline conditions from the Ag electrode were at ca. -1.3V and -1.6V vs SCE, respectively. The different behaviors of 6MP SAMs on gold and silver surface also were comparatively studied(2) The adsorption modes of 4-amino-3-hydrazino-5-mercapto-1,2,4-trizole (NNST) self-assembled monolayers formed on the SERS-active silver and gold electrodes were comparatively studied using surface-enhanced Raman scattering (SERS) and the self assembling procedures were investigated by Raman mapping...
Keywords/Search Tags:Self-assembled Monolayers, Surface enhanced Raman Scattering, Raman mapping, In situ, 6-Mercaptopurine, 2-Mercaptopurine, NNST, Density functional theory
PDF Full Text Request
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