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2 - amino -5 - mercapto- 1, 3,4 - thiadiazole assembled on a metal surface QSAR surface-enhanced Raman spectroscopy and electrochemical studies

Author: SongWei
Tutor: YangHaiFeng
School: Shanghai Normal University
Course: Analytical Chemistry
Keywords: Surface Enhanced Raman Scattering Self-assembly AC impedance AMT Phytic acid sodium salt N'-(4,6 - dimethyl- pyrimidine )-N- acyl thiourea cinnamon
CLC: O626.2
Type: Master's thesis
Year: 2009
Downloads: 82
Quote: 0
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Abstract

Surface Enhanced Raman Scattering (Surface Enhanced Raman Scattering, SERS) spectroscopy is a surface analysis technique with high sensitivity, has been widely used to study the mode of action of interfacial adsorption, the adsorption of molecular orientation and the interface state changes. Situ SERS technology is currently the most commonly used field studies of surface adsorption and interfacial reaction spectroscopy techniques, the spectroscopic methods with conventional electrochemical methods of combining electrochemical genealogy site is at the molecular level electrochemical characterization and research system, new technology, it studies the electrode surface in the orientation of adsorbed molecules and bonded species, identification of the molecular species involved in the electrochemical process and other aspects have outstanding advantages. Self-assembled monolayer (Self-assembledmonolayers, SAMs) and substrate by molecular and molecular physical and chemical effects between spontaneous constitute a class of thermodynamically stable, monolayer arrangement rule, a uniform, stacked, and low defect density and other characteristics . AC impedance is a commonly used electrochemical testing techniques, this method has wide range of frequencies, the characteristics of small perturbations on the system, is a sensitive means of detection, is to study the kinetics of electrode process, the electrode surface phenomena and solid electrolyte conductivity measurement an important tool, is now widely used in the characterization of the electrode surface modified layer. Currently, SERS has been widely used in studies of metal and metal nano-particles morphology of the substrate surface molecules, the arrangement and orientation of molecules in the monolayer film formation, forming intermolecular interactions. SERS with SAMs and electrochemical techniques have been widely used in combination with corrosion inhibitor adsorption mechanism and other aspects of performance. In this paper, metal corrosion inhibitor AMT SERS technology research on gold electrode adsorption behavior. It was found that after about 24 hours to obtain a stable self-assembled monolayer AMT. Formed at low concentrations of AMT-Au layer self-assembly ring and a mercapto group in the two sulfur atoms, the two ring nitrogen atoms and the nitrogen atom of the amino group in flat manner on the surface; at high concentrations formed under the conditions AMT-Au layer self-assembly and ultimately to two sulfur atoms and the nitrogen atom of the amino group in an inclined manner adsorbed on the electrode surface. From the home position at 7.5 × 10-4 mol L-1 formed under the conditions AMT-Au layer self-assembly in the open circuit potential in a ring and a mercapto group and the two sulfur atoms on the amino nitrogen atom in an inclined manner adsorbed on surfaces, when potential changes to-0.4V, the molecules acting on the surface is fully erect; with further potential negative shift, AMT molecule progressively with flat manner on the surface; when the applied voltage is-1.1V, the film is completely desorption. The SERS technology and electrochemical impedance and Tafel curve method in conjunction with, under different pH conditions studied AMT assembly formed in the surface layer of silver corrosion QSAR. SERS found at pH 1 conditions, the assembling layer is formed in a ring and a mercapto group the two sulfur atoms, the two ring nitrogen atoms and the nitrogen atom of the amino group in flat manner on the surface; pH 7 conditions assembling layer formed 2 sulfur atoms and two nitrogen atoms, an amino group away from the silver surface in an inclined manner with silver surface effect; pH 13 formed under the conditions AMT monomolecular layer is formed by 2 sulfur atoms and nitrogen atoms of the amino group compared with the silver surface perpendicular to the way the role. AC impedance and polarization curves of experimental results showed that under the conditions at pH 1 AMT formed monomolecular film structure has the best anti-corrosion. As a single AMT inhibitor in use will encounter pitting the same problem, this paper self-assembly technique in the use of mixed silver surface phytate / AMT composite self-assembled layer, to improve corrosion inhibitor effect of a single. The formed using SERS characterize composite layer; electrochemical impedance and Tafel curves found that the formed composite layer AMT assembly than a single layer has better corrosion performance. Additionally, this article on the use of SERS and in situ SERS silver electrode N'-(4,6 - dimethyl-pyrimidine)-N-cinnamon acylthiourea (code CAS-1) SAMs were studied. SERS found CAS-1 in the silver surface to form a stable self-assembled layer. Situ SERS experimental results show that the open circuit potential of spectral information found molecules N ^{14 , N ^{11 and N ^{16 as adsorption sites point, parallel to the benzene ring, a pyrimidine ring acting perpendicular to the silver surface compared; the applied voltage is-0.3V, the molecules N ^{14 , N ^{11 and N ^{16 as adsorption sites, benzene tilt, pyrimidine ring acting perpendicular to the silver surface; at-1.0V, the molecules with N ^{14 , N ^{16 as adsorption sites point away from the surface a benzene ring, a pyrimidine ring acting parallel to the electrode surfaces.}}}}}}}}

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