Spectroscopy SERS

AC Impedance spectroscopy, 237 Auger electron spectroscopy, AES, 254 High resolution electron energy loss spectroscopy, HREELS, 43, 69 Infrared spectroscopy, IRS, 39, 69 Surface enhanced Raman spectroscopy, SERS, 256... 

The physical methods mostly require ultra high vacuum conditions having the disadvantage of not being applicable directly to solvent swollen films, but recent developments of in situ measurements in SIMS X-ray diffraction surface enhanced Raman spectroscopy (SERS) and scanning electrochemical tunneling microscopy... 

Well-defined CdS/CdSe superlattices have been formed by means of ECALE [74]. In these structures the CdS component - and not CdSe - suffered from substantial crystallographic strain as was evidenced by surface-enhanced Raman spectroscopy (SERS) - a valuable tool for characterizing the superlattice phonons in electrochemical or other ambient environments. Torimoto et al. reported quantum confinement in superlattices of ZnS/CdS grown by ECALE [75]. 

In most work on electrochemical systems, use is made of two effects that greatly enhance the Raman signals. One is resonance Raman spectroscopy (RRS), wherein the excitation wavelength corresponds to an electronic transition in an adsorbed molecule on an electrode surface. The other effect is surface-enhanced Raman spectroscopy (SERS), which occurs on certain surfaces, such as electrochemically roughened silver and gold. This effect, discovered by Fleischmann et al. (1974), yields enhancements of 10 to 10 . The vast majority of publications on Raman studies of electrochemical systems use SERS. The limitations of SERS are that it occurs on only a few metals and the mechanism of the enhancement is not understood. There is speculation that only a small part of the surface is involved in the effect. There is a very good review of SERS (Pemberton, 1991). 

Pettinger, B., Philpott, M. R. and Gordon, J. G. (1981) Contribution of specifically adsorbed ions, water, and impurities to the surface enhanced Raman spectroscopy (SERS) of Ag electrodes. 

Surface Enhanced Raman Spectroscopy (SERS), 176, 184, 194 Surface X-Ray Scattering (SXS), 247-248... 

Generally, it is most likely that metal NPs are stabilized by the aggregates of the non-functionalized imidazolium ILs rather than by the isolated ions. In addition, the interaction between ILs and the metal NPs have been evidenced by X-ray photoelectron spectroscopy (XPS), small-angle X-ray scattering (SAXS), isotope labeling, and surface-enhanced Raman spectroscopy (SERS) techniques. 

Fortunately, in favorable cases enhancement mechanisms operate which increase the signal from the interface by a factor of 105 — 106, so that spectra of good quality can be observed - hence the name surface-enhanced Raman spectroscopy (SERS). However, these mechanisms seem to operate only on metals with broad free-electron-like bands, in particular on the sp metals copper, silver and gold. Furthermore, the electrodes must be roughened on a microscopic scale. These conditions severely limit the applicability of Raman spectroscopy to electrochemical interfaces. Nevertheless, SERS is a fascinating phenomenon, and though not universally applicable, it can yield valuable information on many interesting systems, and its usefulness is expected to increase as instrumentation and preparation techniques improve. 

Some characteristics of, and comparisons between, surface-enhanced Raman spectroscopy (SERS) and infrared reflection-absorption spectroscopy (IRRAS) for examining reactive as well as stable electrochemical adsorbates are illustrated by means of selected recent results from our laboratory. The differences in vibrational selection rules for surface Raman and infrared spectroscopy are discussed for the case of azide adsorbed on silver, and used to distinguish between "flat" and "end-on" surface orientations. Vibrational band intensity-coverage relationships are briefly considered for some other systems that are unlikely to involve coverage-induced reorientation. 

Surface-enhanced Raman spectroscopy (SERS) has also been employed to characterize metal catalyst surfaces [103], The low sensitivity and severe conditions required for the signal enhancement have limited the use of this technique [104], but some interesting work has been published over the years in this area, including studies on model liquid-solid interfaces [105],... 

Surface-enhanced Raman spectroscopy (SERS) has been widely used to study the interaction of solvent molecules with the electrode surface, including orientation at the interface. The first observation of the Raman... 

Cation radicals of several metallated TPP and OEP complexes were reported to have unique IR active ring modes (21. These absorptions were observed in the region 1250-1290 cm for TPP complexes and 1520-1570 cm for OEP complexes. IR and raman active modes have also been observed for several different reduced oxygen species adsorbed on various metal substrates. Observations of the adsorption of oxygen on silver by surface enhanced raman spectroscopy (SERS) 22), show superoxide molecules (O2) have a frequency of 1053 cm, and peroxide (0 ) of 697 cm. This same study reported additional peaks were observed at 815 cm and 1286... 

In surface-enhanced Raman spectroscopy (SERS) samples are adsorbed onto microscopically roughened metal surfaces. Spectra are the intensities and frequencies of scattered radiation originating from a sample that has been irradiated with a monochromatic source such as a laser. SERS spectra are of molecules that are less than 50 A from the surface. 

Ever since Albrecht and Creighton [85], and Jenmarie and van Duyne [86], observed that the Raman cross-section for pyridine absorbed on a roughened silver electrode was larger than that in solution by six orders of magnitude, surface enhanced Raman spectroscopy (SERS) has steadily gained ground in analytical instrumentation. The sensitivity of this technique... 

Raman spectroscopy (SERS) technique was also employed [27]. 

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