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Studies On Surface Enhanced Raman Scattering In Electrochemical System And Colloid-modified Electrode

Posted on:2006-11-29Degree:MasterType:Thesis
Country:ChinaCandidate:R WenFull Text:PDF
GTID:2121360152486844Subject:Optics
Abstract/Summary:PDF Full Text Request
Following the initial discovery of surface enhanced Raman scattering (SERS) from pyridine at electrochemically roughened Ag electrodes, the main SERS studies have concerned adsorption processes at molecular levels. SERS technology, using silver, gold, or other noble metals as substrates, has been a powerful and sensitive instrumental tool for obtaining detailed information of adsorbed molecules, such as the adsorption configuration of molecules and the interaction mechanism of the molecules with the surface of the substrate. It is well known that potential is an important factor influencing surface adsorption and reaction. The adsorption behavior of the adsorbate on the substrate would be greatly affected by the surface configuration of the adsorbate and the applied electrode potential in electrochemically system. At the same potential, if the surface configurations of adsorbates are different, the adsorption patterns of the adsorbates may be different though the composing of them is same. At different applied potential, the adsorption behaviors of the same adsorbates are also probably different.Employing photons as probes, Raman spectroscopy is potentially an ideal technique for studying chemical structures and physical interface phenomena. The photons with ultraviolet (UV) frequency have high energy, which could induce resonance or near resonance transitions between electron energy levels of molecules. Moreover, UV Raman can avoid the fluorescence. Due to those merits of UV Raman, we have obtained high-quality surface Raman spectra of p-hydroxybenzoic(PHBA) on roughened Au surface, which are difficult to be observed at NIR or visible excitation.In electrochemistry system, SERS effect may be restricted at some extent owing to the intrinsic experimental method. There have lots of researches center on how to modify the normally rough electrode to obtain more sensitive SERS substrate. In the present work, roughened silver electrode modified with silver nanoparticles is used asa substrate, on which high-quality SERS spectra of isonicotinic acid (PNBA) were obtained, indicating that the silver-modified silver electrode was a highly SERS-active substrate. It mainly arose from two reasons; one reason was that the roughened silver surface may probably facilitate the silver nanoparticles to aggregate uniformly and compactly on it, and the other reason was that the silver nanoparticles modified on the roughened silver surface took an important action of magnifying the surface local electric field. Moreover, using silver-modified silver electrode the high-quality SERS on the single molecular level is obtained.
Keywords/Search Tags:Surface Enhanced Raman Scattering (SERS), Ultraviolet (UV) Raman Spectroscopy, silver electrode, gold electrode, potential-dependence, silver nano-particles, modified electrode, adsorption behavior
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