Surface-enhanced Raman scattering potential effects

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). 

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. 

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. 

In general, Raman scattering suffers from extremely small cross sections, however, the effect literally appears in a new light, when surface enhanced Raman scattering (SERS) takes place in the local optical fields of metal nanostructures. The effect combines high structural information content and selectivity with extremely high detection sensitivity down to the single molecule level and the potential to probe nanometer scaled volumes. The second section of the book includes chapters that demonstrate the application of SERS in the biomedical field. 

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