SURFACE ENHANCED RAMAN SPECTROSCOPY FROM ELECTRODE/SOLUTION INTERFACE (PHOTOCHEMISTRY, SURFACTANT, ENHANCEMENT).
Item
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Title
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SURFACE ENHANCED RAMAN SPECTROSCOPY FROM ELECTRODE/SOLUTION INTERFACE (PHOTOCHEMISTRY, SURFACTANT, ENHANCEMENT).
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Identifier
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AAI8708324
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identifier
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8708324
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Creator
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SUN, SONGCHENG.
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Contributor
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Ronald L. Birke | John R. Lombardi
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Analytical
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Abstract
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The application of the technique of surface enhanced Raman spectroscopy (SERS) to the study of electrode/solution interfaces is described. We have observed that pyridinium is not directly adsorbed on a Ag electrode surface, rather, it forms an ion pair with a specifically adsorbed chloride anion. We have measured the pH at the outer-Helmholtz plane based on the relative SERS intensity of pyridinium and pyridine, and found that the surface pH is much different from the bulk solution pH. It is a function of chloride concentration and electrode potential.;The interaction of a Ag electrode surface with different types of surfactants has been determined with the SERS technique. The strength of the interaction is found to be different depending on the charge types of the head groups. A head-on orientation is found for all types of surfactants when the potential is on the positive side of -0.8 V vs. SCE, but a reversed orientation is formed when the potential is on the negative side of -0.8 V. The change of the hydrophilic properties of the Ag electrode and an additional enhancement at negative potentials is considered due to the formation of a layer of hydrogen film.;The adsorption behavior of methyl viologen has been studied on a Ag surface by both SERS and cyclic voltammetry. The adsorption peak can be well separated from diffusion peaks in cyclic voltammetry by choosing proper conditions. The surface coverage is measured and the SERS enhancement factor is calculated based on the adsorption current of methyl viologen.;Finally, a surface induced photochemical reduction of p-nitrobenzoate is observed on both Ag island films and electrode/solution interfaces by SERS measurements. Our observations indicate that the chemical reactions which occur on the SERS activated surface is not due to a laser heating effect. The photolysis rate is studied as a function of the photon flux of excitation, the excitation frequency of the laser light and the electrode potential. A charge transfer mechanism, similar to the same mechanism for SERS, can be employed to interpret the enhancement of the photochemistry on roughened metal surfaces.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
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Program
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Chemistry
