A study of the surface Raman spectra of triphenylmethane dyes on colloidal silver.
Item
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Title
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A study of the surface Raman spectra of triphenylmethane dyes on colloidal silver.
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Identifier
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AAI9108162
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identifier
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9108162
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Creator
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Persaud, Indira Vedawatee.
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Contributor
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Adviser: William E. L. Grossman
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Date
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1990
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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 usefulness of Surface Enhanced Raman Scattering (SERS) as a viable analytical technique has been explored in this study. This investigation was carried out by a study of the structural changes that some of the triphenylmethane dyes undergo when complexed to a silver surface. An assessment of the solution and surface vibrational spectra has led to the conclusion that the dye molecules are most likely lying parallel to the sol surface and adopting C{dollar}\sb3{dollar} symmetry. It is not evident that a new surface complex is formed when these dyes are adsorbed onto the silver surface, but there is evidence for interactions between the Ag sol and the dyes. Very few changes are noted for the N-phenyl stretching mode; most of the vibrational changes are localized at the C{dollar}\sp+{dollar}-C bonds; hence we have concluded that the central carbonium ion is the major center of interaction.;The utility of SERS as a quantitative tool has been also examined. The SERS intensity of the analyte peaks were measured relative to the O-H stretching band of water and corrected for absorption. A linear calibration curve over a wide concentration range is not observed. SERS intensities were found to be independent of the concentration from 5 {dollar}\times{dollar} 10{dollar}\sp{lcub}-7{rcub}{dollar}M to 5 {dollar}\times{dollar} 10{dollar}\sp{lcub}-5{rcub}{dollar}M. The intensity of the dye peaks in the surface Raman spectra were found to be dependent on a number of factors including the sol's age. It would appear that some degree of aggregation is necessary before a surface Raman spectrum could be observed at concentrations {dollar}\leq{dollar}10{dollar}\sp{lcub}-6{rcub}{dollar}M for crystal violet and pararosaniline. A limit of detection of 5 {dollar}\times{dollar} 10{dollar}\sp{lcub}-8{rcub}{dollar}M was obtained for all of the three dyes studied.;Surface enhancement factors have been estimated by a comparison of the relative Raman cross-section of the dyes in solution and adsorbed on the sol. After correcting for absorption and for the number of molecules actually lying on the sol's surface (assuming monolayer coverage), enhancement factors ranging from 10{dollar}\sp5{dollar}-10{dollar}\sp6{dollar} were obtained.
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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.
