Surface plasmon wave Raman spectroscopy

In order to make meaningful physical measurements on monolayer and multilayer L-B films, it is essential that the films be characterized to determine the molecular structure, unformity of the film and layer-to-layer structural correlation. To probe the molecular structure, our research group has utilized a variety of spectroscopic techniques such as u.v.-visible spectroscopy, ATR-IR, wave-guide Raman, surface-plasmon wave Raman spectroscopy and inelastic electron tunneling. The spectroscopic techniques... 

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. 

In these sensors, the intrinsic absorption of the analyte is measured directly. No indicator chemistry is involved. Thus, it is more a kind of remote spectroscopy, except that the instrument comes to the sample (rather than the sample to the instrument or cuvette). Numerous geometries have been designed for plain fiber chemical sensors, all kinds of spectroscopies (from IR to mid-IR and visible to the UV from Raman to light scatter, and from fluorescence and phosphorescence intensity to the respective decay times) have been exploited, and more sophisticated methods including evanescent wave spectroscopy and surface plasmon resonance have been applied. 

A number of methods are available for the characterization and examination of SAMs as well as for the observation of the reactions with the immobilized biomolecules. Only some of these methods are mentioned briefly here. These include surface plasmon resonance (SPR) [46], quartz crystal microbalance (QCM) [47,48], ellipsometry [12,49], contact angle measurement [50], infrared spectroscopy (FT-IR) [51,52], Raman spectroscopy [53], scanning tunneling microscopy (STM) [54], atomic force microscopy (AFM) [55,56], sum frequency spectroscopy. X-ray photoelectron spectroscopy (XPS) [57, 58], surface acoustic wave and acoustic plate mode devices, confocal imaging and optical microscopy, low-angle X-ray reflectometry, electrochemical methods [59] and Raster electron microscopy [60]. 

If one includes the employment of evanescent light waves in spectroscopic studies in the near-field area. Knoll and coworkers are among the first who reported on near-field Raman spectroscopy , though this approach was termed at that time (the early 1990s) as surface plasmon field-enhanced Raman spectroscopy and microscopy [104],... 

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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