Raman Spectroscopy of Biomolecules at Electrode Surfaces

One of the problems of SEES is that it is relatively easy to achieve but difficult to control. This has led, and continues to lead, to publications that claim to have new surfaces that show SEES but which in reality offer no advantage over existing roughened surfaces, or publications that claim insight into the mechanism of the phenomenon but which are in fact readily explained within the basis of current understanding of SEES [6]. As a consequence a vast and somewhat confusing literature has built up around the subject over the past 30 years and this is a 

Advances in Electrochemical Science and Engineering. Edited by Richard C. Alkire, Dieter M. Kolb, and Jacek Lipkowski 

The intensity for a transihon from an initial state i to a final state f is given by [21, 22] 

SERS and Surfece-Enhanced Resonant Raman Spectroscopy 

In contrast electromagnetic enhancement [6] relies on the intensification of the local electromagnetic field at the metal surface and the interaction of this localized electromagnetic field with the molecules close to, but not necessarily directly in contact with or chemisorbed at, the metal surface. The electromagnetic enhancement is of longer range than the chemical enhancement decaying over a distance of the order of 50 to 100 nm. 

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It is appropriate to conclude this part of the chapter, before going on to review the literature on SE(R)RS of biomolecules at electrode surfaces, by briefly describing tip-enhanced Raman spectroscopy (TERS) since this rapidly developing technique offers the potential for studies at molecular resolution. In TERS a metal nanoparticle or metalized tip (usually Ag or Au) with an apex diameter of about 25 nm is illuminated by a laser as it is scanned across the surface (Figure 6.14). The tip is used to locally amplify and confine the electromagnetic field, in effect creating a local hotspot which can be scanned across the surface. The first examples of this approach were reported in 2000 [193-195]. Since then the approach has been... 

With the extremely high enhancement of the Raman scattering signals in the immediate vicinity of the charged metal-surface (electrode, Ag colloidal particles, activated nano-TLC plates) it is possible to identify the adsorbed parts of the methylated guanine derivatives and to study their configuration at very low concentrations. These results demonstrate new possibilities of Raman-spectroscopy to obtain high resolution vibrational spectra of adsorbed biomolecules. 

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