Surface electromagnetic wave enhancement

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

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. 

The surface enhancement is ascribed to the occurrence of two separate effects, electromagnetic and chemical (70). The electromagnetic effect arises from small surface structures arising in the ORC that cause strong local increases of the electric fields of the excitation and scattered radiation via surface plasmon waves. The chemical effect is attributed to interactions between the adsorbed molecule and the metal surface which lead to electronic (charge-transfer) transitions between molecule and metal. The result is a res-onance-Raman-like effect. Since both effects operate only over very small distances, SERS is specific for molecules at the electrode surface. 

The electric field of the electromagnetic wave at the surface is a vectorial sum of the fields of the incident and reflected waves. Depending on the phase shift of the reflected wave, the sum gives enhancement or attenuation of the electric field. The components of the MSEFS of the IR photon at the surface in directions perpendicular and parallel to the surface (z = 0) can be calculated with the help of the following formulas [19] ... 

However, in the presence of a thin film at the air-metal interface, there is no enhancement of ( ) at the metal surface, as might be concluded based on the above consideration. The reason will be apparent if one analyzes the boundary conditions for the electromagnetic wave (1.4.7°). The continuity of the tangential components of the electric field and the perpendicular component of the electric displacement, D = eE, can be approximated for a three-phase system as [99, 101]... 

Metal nanocrystals also interact strongly with electromagnetic waves and offer remarkable properties due to the localized surface plasmon resonance (SPR) that induces, through optical excitation, very intense local electrical fields. This property can be exploited for surface-enhanced Raman spectroscopy (SERS) and SPR-based... 

Additional applications of the SPR phenomenon include using the surface plasmon electromagnetic waves to excite emission of surface-bound chromo-phores, to enhance Raman spectra (surface-enhanced Raman spectroscopy), and as surface-bound light in optical microscopy. 

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