Time-resolved surface enhanced Raman scattering studies of surface photochemistry and electrochemistry.
Item
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Title
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Time-resolved surface enhanced Raman scattering studies of surface photochemistry and electrochemistry.
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Identifier
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AAI9605690
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identifier
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9605690
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Creator
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Zhang, Wei.
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Contributor
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Co-Advisers: Ronald L. Birke | John R. Lombardi
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Date
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1995
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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 | Chemistry, Physical | Chemistry, Organic
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Abstract
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Applications of time resolved surface enhanced Raman scattering (TRSERS) techniques for the study of surface photochemistry and electrochemistry were demonstrated.;As an example of TRSERS applications in surface photochemistry studies, direct photoinduced charge transfer from adsorbed flavin mononucleotide (FMN) to a Ag electrode was observed by TRSERS and complementary experiments. Two short lived photoproduct radical ion intermediates with life time of 775ns and 1.5{dollar}\mu{dollar}s were observed and confirmed as enol-keto forms of a photo-oxidized FMN monocation radical by TRSERS of FMN and deuterated FMN with the help of normal mode calculations. New mechanisms of photo-induced charge transfer between FMN and a Ag electrode and for the photogalvanic effect on a dye modified electrode were proposed as a result of the experiments.;As an example of TRSERS applications in an electrochemical study, p-Nitrobenzoic acid (PNBA) was studied by TRSERS following the application of a double potential step to a Ag electrode. The spectral bands of three stable intermediate products, p-nitrosobenzoate, hydroxylamine, and azoxy compounds were observed. In addition, the transient bands of an unstable intermediate were seen at 996, 1233, and 1580cm{dollar}\sp{lcub}-1{rcub}{dollar} with a life time of about 70ms during the oxidation process of the hydroxylamine compound which itself is generated electrochemically by a 200ms potential pulse. We suggest these bands represent the p-nitrosobenzoate free radical anion intermediate formed during the oxidation of the hydroxylamine compound.;In addition, three redox states of FMN and interactions of FMN with a Ag electrode were studied by SERS, UV/Vis absorption spectrophotomerty and normal mode calculations. The adsorption site and orientation of FMN on a Ag electrode were found depending on the Ag electrode surface potential. The SERS spectrum of FMN hydroquinone was reported for the first time.
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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.
