Surface-enhanced Raman scattering SERS effect

Nevertheless, there has been a renewed interest in Raman techniques in the past two decades due to the discovery of the surface-enhanced Raman scattering (SERS) effect, which results from the adsorption of molecules on specially textured metallic surfaces. This large enhancement was first... 

The metallic nanocrystals are remarkable due to their localized surface plasmon resonance (SPR) phenomenon, that is, the excitation of surface plasma by light. It ensures these nanocrystals to be color based sensors (Homola et al., 1999 Kelly et al., 2003). The metallic nanocrystals could also sensitize the Raman signals from their adsorbed organic molecules. This surface enhanced Raman scattering (SERS) effect potentially raises the detection sensitivity to single molecule level (Kneipp et al., 1997 Nie and Emery, 1997). 

Raman spectroscopy is not particularly surface sensitive but a surface enhanced Raman scattering (SERS) effect is observed on some metals (copper, gold, silver, nickel etc). On an appropriately prepared (roughened) surface or on metal colloids the surface coverage of molecules can be measured by Raman spectroscopy with high sensitivity. 

The Ag experiments are important since it is particularly feasible to detect and characterize adsorbed species by the Surface-Enhanced Raman Scattering (SERS) effect. Studies have indicated [56-58] that strong irreversible adsorption of cytochrome c occurs at Ag and that, for the less stable Fe(III) state, this is accompanied by a change in conformation. Direct evidence for this came from the spectroscopically determined reduction potential for the adsorbed protein, which showed a large negative shift, and detection of vibrations associated with non-native forms. 

STM-Raman spectroscopy utilizes the effect that Raman scattering is enhanced for a molecule in the vicinity of a metal nanostructure. This enhancement effect is generally called surface-enhanced Raman scattering (SERS). When a sharp scanning probe, such as a tunneling tip for STM, is used as a metal nanostructure to enhance Raman intensity, it is called tip-enhanced Raman scattering (TERS). The concept of STM combined with Raman spectroscopy is presented in Figure 1.1. 

Surface-enhanced Raman scattering (SERS) is a candidates for resolving this issue. Since the SERS effect is observed only at metal surfaces with nanosized curvature, this technique can also be used to investigate nanoscale morphological structures of metal surfaces. It is thus worth investigating SERS under oscillatory electrodeposition conditions. The author of this chapter and coworkers recently reported that... 

The combination of surface enhanced Raman scattering (SERS) and infrared reflection absorption spectroscopy (IRRAS) provides an effective in-situ approach for studying the electrode-electrolyte interface. The extreme sensitivity to surface species of SERS is well known. By using polarization modulation of the infrared beam for IRRAS, the complete band shape is obtained without modulating the electrode potential. 

Surface-enhanced Raman scattering (SERS) has emerged as a powerful technique for studying species adsorbed on metal films, colloidal dispersions, and working electrodes. SERS occurs when molecules are adsorbed on certain metal surfaces, where Raman intensity enhancements of ca. 105-106 may be observed. The enhancement is primarily due to plasmon excitation at the metal surface, thus the effect is limited to Cu, Ag, and Au, and a few other metals for which surface plasmons are excited by visible radiation. 

As for Raman spectroscopy one may expect resonance Raman effect and/or surface-enhanced Raman scattering (SERS). By using these effects, the Raman spectrum of a monolayer film may be enhanced by 103-106. Resonance Raman spectroscopy is useful for exploring the electronic structure of monolayers with a chromophore and SERS technique is applied to study structure, orientation, and interactions of monolayers on a silver or gold surface. 

Watanabe T, Yanagihara N, Honda K, Pettinger B, Moerl L (1983) Effects of underpotentially deposited T1 and Pb submonolayers on the surface-enhanced Raman-scattering (SERS) from pyridine at Ag electrodes. Chem Phys Lett 96(6) 649-655... 

Etchegoin PG, Galloway C, Le Ru EC (2006) Polarization-dependent effects in surface-enhanced Raman scattering (SERS). Phys Chem Chem Phys 8(22) 2624—2628... 

SIERA Surface-enhanced infrared absorption As in the case of surface-enhanced Raman scattering (SERS), molecules adsorbed on metal island films or particles exhibit intense infrared absorption several folds higher than what one would expect from conventional measurements without the metal. This effect is referred to as surface-enhanced infrared absorption (SEIRA). 

This effect is known as surface enhanced Raman scattering (SERS) [10-12]. The SERS effect has been widely investigated for various molecules adsorbed on rough metallic surfaces or on metallic clusters in colloids. Reviews on this topic can be found in Refs. [12-15]. The enhancement of normally Raman-active modes is a consequence of the enhancement of the electric field of the incoming and scattered radiation in the vicinity of a rough metal film upon coupling with the dipolar plasmon resonances in the metal clusters. This enhancement affects molecules located up to even 10 nm away from the metal surface [11, 12]. The enhancement factors are essentially determined by the electronic properties of the metal and by the morphology of the metal film. 

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