Surface Enhanced Raman Scattering and Electrochemical Characterization of Metal Electrode-electrolyte Interfaces in Nonaqueous Systems (PHD). PDF Download
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Author: Aijin Shen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Aijin Shen
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ISBN:
Category :
Languages : en
Pages : 0
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Author: F. J. Boerio
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Category :
Languages : en
Pages : 3
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Surface-enhanced Raman scattering (SERS) is an analytical technique in which the Raman scattering cross-sections of molecules adsorbed onto the roughened surfaces of certain metals are enhanced by as much as six orders of magnitude compared to their value for normal Raman scattering. Many models have been proposed to explain SERS, but it is now considered that most of the enhancement is related to two mechanisms. The first is associated with the large electric fields that can be induced at the surfaces of metal particles having small radii of curvature. The second is associated with formation of charge-transfer complexes between the adsorbed molecules and the substrate. Enhancement due to the charge transfer mechanism is obtained only for molecules immediately adjacent to the surface, but enhancement due to electromagnetic mechanism may extend several monolayers away from the surface. Considering that normal Raman scattering by polymers is weak and that scattering by molecules adjacent to the substrate is strongly enhanced, it is evident that SERS can be used for non-destructive characterization of interfaces between polymer films and metals as long as the films are not so thick that scattering by the bulk of the film is comparable in intensity to SERS from the interface. Keywords: DD Form 1473, Nondestructive characterization, Polymer/Metal interfaces, Surface-enhanced raman scattering, SERS, Adsorption, Silver, Acrylic adhesive system.
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Category : Dissertations, Academic
Languages : en
Pages : 806
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Author: Héctor D. Abruña
Publisher:
ISBN:
Category : Electrochemistry
Languages : en
Pages : 616
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Author: Dipankar Roy
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ISBN:
Category :
Languages : en
Pages : 183
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Author: Thomas Touzalin
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Category :
Languages : en
Pages : 0
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The in situ investigation of electrochemical interfaces structures at the nanoscale is a key element in the understanding of charge and electron transfer mechanisms e.g. in the fields of energy storage or electrocatalysis. This thesis introduces the implementation of tip-enhanced Raman spectroscopy (TERS) in liquid and in electrochemical conditions enabling the nanoscale analysis of electrified solid/liquid interfaces through the strong and local electric field enhancement at gold or silver scanning tunneling microscopy (STM) probes. The ability of TERS to image inhomogeneities in the coverage density of a self-assembled monolayer (SAM) through a layer of organic solvent on gold was demonstrated. A TERS-inspired analytical tool was also developed, based on a TERS tip used simultaneously as a single-hot spot surface-enhanced Raman spectroscopy (SERS) platform and as a microelectrode (EC tip SERS). The reduction of an electroactive SAM could then be monitored by electrochemical and in situ SERS measurements. In situ electrochemical STM-TERS was also evidenced through the imaging of local variations of the electric field enhancement on peculiar sites of a gold electrode with a lateral resolution lower than 8 nm. Finally TERS also demonstrated to be efficient in investigating the structure of organic layers grafted either by electrochemical reduction or spontaneously. This work is therefore a major advance for the analysis of functionalized surfaces.
Author: M. A. Tadayyoni
Publisher:
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Category :
Languages : en
Pages : 32
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Surface-enhanced Raman (SER) spectra have been obtained at the silver-aqueous interface for nine Cr III, Co III, Ru II, and Rh III ammine or ethylenediamine complexes containing one or more thiocyanates as surface bridging groups. These complexes provide stereochemically well-defined adsorbates having at least one sulfur surface binding site but with electronic properties that differ substantially from thiocyanate itself. The dependence of the SER spectra were examined in each case over a potential range where the complexes are stable with respect to reduction or oxidation, and where the adsorbate coverage remained close to a monolayer. The adsorbate coverage could be evaluated in several cases from the faradaic charge required for one-electron reduction. SER spectra were obtained using a spectrograph-optical multichannel analyzer (OMA) as well as a conventional scanning spectrometer. This enabled the rapid reversible component of the SERS potential dependence to be separated from the irreversible signal decay associated with surface rearrangement. SERS bands due to metal ammine and internal ammine vibrations were observed in addition to those associated with internal thiocyanate and ligand-surface vibrations.
Author: M. J. Weaver
Publisher:
ISBN:
Category :
Languages : en
Pages : 26
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Surface-Enhanced Raman Scattering (SERS) obtained as a function of electrode potential for chloride, bromide, iodide, thiocyanate, azide, and cyanide adsorbed at roughened silver electrodes are compared with corresponding surface concentration-potential data extracted from differential capacitance measurements in order to examine the relation between SERS and surface coverage for these structurally simple adsorbates. After generating SERS by means of an oxidation-reduction cycle, it was found that altering the potential to a more negative value, where the adsorbate coverage fell below a monolayer, corresponded closely in most cases to the onset of a potential-dependent decay in the SERS intensity. Monitoring the potential dependence of the Raman intensity with an Optical Multi-channel Analyzer as well as with a conventional scanning spectrometer allowed a rapid reversible component of the potential dependence to be separated from an additional irreversible signal decay associated with the loss of Raman-active sites. The present results suggest that the adsorption energetics of the Raman-active surface sites do not differ substantially from those for the sites occupied by the majority of the adsorbate.
Author: Ujjal Kumar Sur
Publisher:
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Category : Science
Languages : en
Pages :
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The steady and fast development of surface and interfacial science have set up innovative openings for new diagnostic probes for analytical characterization of the adsorbates and determination of the microscopic structure of surfaces and interfaces. Regrettably Raman spectroscopy, being a weak scattering surface phenomenon, had seized no part in it, until the discovery and development of Surface Enhanced Raman Scattering (SERS) in the early 1970's that has opened up broad research fields both in the physics and chemistry of interfaces. The discovery of SERS by Fleischmann and coworkers in 1974 at the University of Southampton, United Kingdom is closely connected with the electrochemical systems. They reported an extraordinary million-fold enhancement of weak Raman signal from pyridine molecules adsorbed onto electrochemically roughened silver electrode compared to that from free molecules in liquid environment. In early 1976, Richard P. Van Duyne and David Jeanmaire at Northwestern University observed the effect and in early 1977, M. G. Albrecht and J. A. Creighton reported similar observation. This review article deals with the development of SERS research with special importance is given to the fabrication of various SERS-active substrates, mechanism of SERS effect and its various potential applications ranging from sensors to biomedical applications.
Author: James McBreen
Publisher: The Electrochemical Society
ISBN: 9781566772372
Category : Science
Languages : en
Pages : 208
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