Surface enhanced Raman scattering SERS

Raman spectroscopy has been used to examine earbon fibers [96], the effect of processing variables [97] and the effeet of various treatments [98]. Chase has described Fourier Transform Raman Speetroseopy [99]. 

The first SERS experiments were performed with electrochemically roughened electrodes and metal colloids, and many other types of suitable SERS substrates are known - e.g. metal island films, metal films over nanoparticles (see Fig. 4.58, below) or rough substrates, gratings, and sputter-deposited metal particles. 

SERS is usually restricted to specially prepared active surfaces. A broad range of other surfaces also becomes accessible to SERS spectroscopy after special preparation techniques  

For overlayer thicknesses of a few atomic or molecular layers, the supporting metal can produce surface-enhanced fields at the surface of the overlayer. Then, composition and structure of the overlayer surface can be analyzed by SERS spectroscopy [4.291]. 

According to the SERS selection rules, the spectral profile of the adsorbate is strongly dependent on the orientation of the main molecular axes with respect to the surface . Thus, SERS intensities would also provide valuable information about the molecular orientation that the adsorbate adopts once adsorbed on the metal surface. For this reason, symmetry assignments are central to the discussion of molecular orientation of adsorbed species on the surface of island or colloidal metal particles. If the molecules, i.e. N4 macrocycles, are oriented face-on the metal surface, with the N atoms face to the metal atoms, the C4 axis of the molecule and the normal to the surface are parallel thus, the most symmetric vibrational modes, that derive their intensity from the zz-component of the polarisability derivative tensor a z will be the most intense at the surface plasmon resonance frequency and to the red of that frequency. 

Most of SERS studies use the conventional Raman apparatus the signal enhancement depends on the characteristics of the surface, the nature of the adsorbate, and on the incident wavelength. Colloids and electrodes surface preparation has been largely reported  

This model also explains qualitatively some of the other experimental observations. A limited number of substrates active in SERS implies that the frequencies of localized SPs for them are in the visible spectral range commonly used for Raman spectroscopy. In addition, the imaginary part of the dielectric function for those metals is very small at the SP frequency, ensuring small losses in the substrate. As the SERS enhancement is proportional to i co)f] co ), it acquires large values only if the resonance condition with lo- 

Many techniques are used to fabricate the required nano-structures including aggregated colloidal metal sols, electrochemically roughened electrodes, evaporated and or cured metal films. 

The enhancement can even be pushed further by 3 orders of magnitude by using laser light, which s in resonance with an electronic transition of the substances. This technique is called surface enhanced resonance Raman scattering ( resonant SERS ). Applications of SERS include not only the detection of molecules, but also the investigation of the structure and function of large biomolecules as well as the analysis of chemical processes at interfaces. SERS is particularly well suited for sandwich-type immunoassays and hybridization assays. 

The SERS intensities for standard colloids or often quite weak, but can be easily enhanced by binding a strong chromophore near the surface of a metal cluster. Such labeled metal-clusters are adsorbed to a metal chip surface, preferably in a sandwich type assay. With a protein having a strong chromophore itself it can act as the label and analyte at the same time, binding the colloidal particle to the SERS active surface. In an ideal setup the protein is then sandwiched between two SERS active clusters. If the 

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Kneipp K, Wang Y, Kneipp FI, Perelman L T, Itzkan I, Dasari R R and Feld M S 1997 Single molecule detection using surface-enhanced Raman scattering (SERS) Phys. Rev. Lett. 78 1667-70... 

Surface-enhanced Raman scattering (SERS) and differential capacitance methods have been used to study the interfacial solvent structure and... 

Efrima, S. Eisenberg, H. Surface-Enhanced Raman Scattering (SERS) Physical Chemistry of Synthetic Polyelectrolytes 16... 

STM-Raman spectroscopy utilizes the effect that Raman scattering is enhanced for a molecule in the vicinity of a metal nanostructure. This enhancement effect is generally called surface-enhanced Raman scattering (SERS). When a sharp scanning probe, such as a tunneling tip for STM, is used as a metal nanostructure to enhance Raman intensity, it is called tip-enhanced Raman scattering (TERS). The concept of STM combined with Raman spectroscopy is presented in Figure 1.1. 

Surface-enhanced Raman scattering (SERS) is a candidates for resolving this issue. Since the SERS effect is observed only at metal surfaces with nanosized curvature, this technique can also be used to investigate nanoscale morphological structures of metal surfaces. It is thus worth investigating SERS under oscillatory electrodeposition conditions. The author of this chapter and coworkers recently reported that... 

Narayanan V., Begun G., Stokes D., Sutherland W., Vo-Dinh T., Normal Raman and surface-enhanced Raman scattering (SERS) spectra of some fungicides and related chemical compounds,/. Raman Spectrosc., 1992 23 281-286. 

Murphy T., Schmidt H., Kronfeldt H., Use of sol-gel techniques in the development of surface-enhanced Raman scattering (SERS) substrates suitable for in situ detection of chemicals in sea-water, Appl. Phys. B, 1999 69(2) 147-150. 

Nevertheless, there has been a renewed interest in Raman techniques in the past two decades due to the discovery of the surface-enhanced Raman scattering (SERS) effect, which results from the adsorption of molecules on specially textured metallic surfaces. This large enhancement was first... 

Kerker M., Electromagnetic Model for Surface-Enhanced Raman-Scattering (Sers) on Metal Colloids, Accounts Chem. Res. 1984 17 271-277. 

Vo-Dinh T., Stokes D.L., Griffin G.D., Volkan M., Kim U.J., Simon M.I., Surface-enhanced Raman scattering (SERS) method and instmmentation for genomics and biomedical analysis, / Raman Spectrosc. 1999 30 785-793. 

Tarabara V.V., Nabiev I.R., Feofanov A.V., Surface-enhanced Raman scattering (SERS) study of mercaptoethanol monolayer assemblies on silver citrate hydrosol. Preparation and characterization of modified hydrosol as a SERS-active substrate, Langmuir 1998 14 1092-1098. 

Measor, P. Lunt, E. J. Seballos, L. Yin, D. Zhang, J. Z. Hawkins, A. R. Schmidt, H., On chip Surface enhanced Raman scattering (SERS) detection using integrated liquid core wave guides, Appl. Phys. Lett. 2007, 90, 211107... 

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. 

Much of this research effort has been directed to the study of the fundamental basis of surface-enhanced Raman scattering (SERS), in order to understand the underlying principles. There have also been many applications of SERS to situations in which in situ vibrational... 

Surface energy, 1 505-506 Surface-enhanced Raman scattering (SERS), 16 486 21 327-328 24 12 Surface-enhanced Raman spectroscopy, silver and, 22 640... 

Surface-enhanced Raman scattering (SERS) has emerged as a powerful technique for studying species adsorbed on metal films, colloidal dispersions, and working electrodes. SERS occurs when molecules are adsorbed on certain metal surfaces, where Raman intensity enhancements of ca. 105-106 may be observed. The enhancement is primarily due to plasmon excitation at the metal surface, thus the effect is limited to Cu, Ag, and Au, and a few other metals for which surface plasmons are excited by visible radiation. 

H. Schmidt, B.H. Nguyen, P. Jens, A. Hans and K. Heinz-Detlef, Kowalewska Grazyna detection of PAHs in seawater using surface-enhanced Raman scattering (SERS), Mar. Pollut. Bull., 49(3) (2004) 229-234. 

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