Surface Enhanced Raman electromagnetic field enhancement

M. (2006) Ahgned silver nanorod arrays for surface-enhanced Raman scattering. Nanotechnology, 17, 2(>70-2(>74, (b) Lu, Y, Liu, G.L., Kim, J., Mejia, Y.X. and Lee, L.P. (2005) Nanophotonic crescent moon structures with sharp edge for ultrasensitive biomolecular detection by local electromagnetic field enhancement effect Nano Letters, 5, 119-124 ... 

Duyne and co-workers estimated enhancement factors on the order of 105 to 106 for pyridine on rough silver electrodes. The value was obtained from a comparison between surface-enhanced and normal bulk Raman signals from pyridine by taking into account the different number of molecules on the electrode and in solution. The size of the enhancement was found to correlate with the electrode roughness, indicating that enhancement occurs via a strong electromagnetic field. On the other hand, the dependence of the... 

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. 

As a result, several schemes including cavity-enhanced Raman [6], photonic crystal-enhanced Raman [7], surface-enhanced Raman [8], etc., have been put forward in an attempt to increase the electromagnetic field strength for excitation. Among them, surface-enhanced Raman scattering (SERS), by far, is one of... 

At this point, it is important to clarify what is meant by the enhancement factor before discussing hot spots further. Typically, the enhancement factor is calculated as the ratio of the detected Raman signal under SERS conditions compared to the signal obtained under normal conditions, for equal numbers of active molecules and surface area exposed to the laser beam. This value is proportional to the intensity of the local electromagnetic field ( ) to the fourth power, i.e., jEj which results from the enhancement of both the incident and emitted photons [15]. Throughout the rest of the chapter, the enhancement factor that is quoted refers to this the enhancement of SERS intensity, rather than that associated with the local electromagnetic field unless otherwise stated. 

The electromagnetic nature of surface-enhanced Raman scattering (SERS) and plasmon-enhanced fluorescence (PEF) involves resonant excitations of localized plasmons (LPs) in the near-field of nanosized noble metal particles or films, coupling them with surrounding scatterers and detection of their secondary emission in the far field. Employment of these plasmonic phenomena are proposed, for example, as a new approach to increase brightness of heavily labeled macromolecules [1]. 

C. D. Keating K. K. Kovaleski M. J. Natan, Heightened electromagnetic fields between metal nanoparticles Surface enhanced Raman scattering from metal-cytochrome c-metal sandwiches. /. Phys. Chem. B 1998,... 

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... 

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