Surface-enhanced Raman spectroscopy electromagnetic enhancement

Alternatively, various analytical methods based on SPR phenomenon have been developed, including surface plasmon field-enhanced Raman scattering (SERS) [7], surface plasmon field-enhanced fluorescence spectroscopy (SPFS) [8-11], surface enhanced second harmonic generation (SHG) [12], surface enhanced infrared absorption (SEIRA) [13], surface plasmon field-enhanced diffraction spectroscopy (SPDS) [14-18], Most of these methods take advantage of the greatly enhanced electromagnetic field of surface plasmon waves, in order to excite a chromophoric molecule, e.g., a Raman molecule or a fluorescent dye. Therefore, a better sensitivity is expected. 

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... 

SEMPA Scanning Electron Microscopy with Polarisation Analysis, 37 SERS Surface Enhanced Raman Scattering, 32 SEW Surface Electromagnetic Waves Spectroscopy, 40 SEXAFS Surface EXAFS, 49... 

The application of the ATR method in Raman spectroscopy provides a unique way to study essentially mirrorlike polished metals, in particular single crystalline surfaces. The ATR method is used to excite surface plasmon polaritons (SPPs) effectively at the smooth metal surface, to improve the sensitivity in Raman spectroscopy by electromagnetic field enhancement [19]. The enhancement of the ATR configuration, as shown in Figs. 8(d and e), with respect to the normal external reflection geometry spans one to three orders, depending on the electrodes and their crystallographic orientations. 

Surface-enhanced Raman spectroscopy (SERS) is based on the amplification of the Raman effect - the inelastic scattering of light at molecules - at nanostructured metal surfaces. If light is scattered at molecules, a dipole moment H is induced to the molecule by an incident electromagnetic field E as described in Eq. 1. Here, oc represents the polarizability of the molecule - a measure to what extent the electric field E is able to disturb the electron density of a molecule out of its equilibrium configuration ... 

Surface-Enhanced Raman Spectroscopy, Fig. 3 Schematic scheme of processes appearing for the electromagnetic cmhancement mechanism... 

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