Surface-enhanced Raman characterization

MOLE, however, is more sensitive than ETIR (<1 samples compared to about 100 p.m ). With surface-enhanced Raman spectroscopy the Raman signal is enhanced by several orders of magnitude. This requires that the sample be absorbed on a metal surface (eg, Ag, Cu, or Au). It also yields sophisticated characterization data for the polytypes of siUcon carbide, graphite, etc. 

Surface active material, 79, 81 Surface characterization, 45, 46 Surface coverage, 37 Surface enhanced Raman scattering, 45 Surface tension, 23, 25... 

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]. 

Olson LG, Lo YS, Beebe TP Jr, Harris JM (2001) Characterization of silane-modified immobilized gold colloids as a substrate for surface-enhanced Raman spectroscopy. Anal Chem 73 4268-4276... 

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. 

The first electrodeposition of a compound superlattice appears to have been by Rajeshwar et al. [219], where layers of CdSe and ZnSe were alternately formed using codeposition in a flow system. That study was proof of concept, but resulted in a superlattice with a period significantly greater then would be expected to display quantum confinement effects. There have since been several reports of very thin superlattices formed using EC-ALE [152, 154, 163, 186], Surface enhanced Raman (SERS) was used to characterize a lattice formed from alternated layers of CdS and CdSe [163]. Photoelectrochemistry was used to characterize CdS/ZnS lattices [154, 186]. These EC-ALE formed superlattices were deposited by hand, the cycles involving manually dipping or rinsing the substrate in a sequence of solutions. 

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],... 

Since most biomolecules normally exhibit medium or low Raman cross sections, an enhancement of the signal intensity for the ability to characterize even low concentrations would be preferable. Besides the application of resonance Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS) is a promising alternative. In doing so the vicinity of molecules to rough noble metal surfaces leads to Raman enhancement factors of 106-108 and even up to 1014 leading to a single molecule detection limit [9]. 

Smejkal P, Siskova K, Vlckova B, Pfleger J, Sloufova I, Slouf M, Mojzes P (2003) Characterization and surface-enhanced Raman spectral probing of silver hydrosols prepared by two-wavelength laser ablation and fragmentation. Spectrochim Acta A 59 2321-2329... 

Plieth W, Dietz H, Anders A, Sandmann G, Meixner A, Weber M, Kneppe H (2005) Electrochemical preparation of silver and gold nanoparticles characterization by confocal and surface enhanced Raman microscopy. Surf Sci 597 119... 

Dieringer JA, McFarland AD, Shah NC, Stuart DA, Whitney AV, Yonzon CR, Young MA, Zhang XY, Van Duyne RP (2006) Surface enhanced Raman spectroscopy new materials, concepts, characterization tools, and applications. Faraday Discuss 132 9-26... 

Khoury CG, Vo-Dinh T (2008) Gold nanostars for surface-enhanced Raman scattering synthesis, characterization and optimization. J Phys Chem C 112 18849-18859... 

Premasiri WR, Moir DT, Klempner MS, Krieger N, Jones G, Ziegler LD (2005) Characterization of the surface enhanced Raman scattering (SERS) of bacteria. J Phys Chem B 109 312-320... 

Caldwell, W. B., Campbell, D. j., Chen, K. M., Herr, B. R., Mirkin, C. A., Malik, A., Durbin, M. K., Dutta, P., and Huang, K. G. A highly ordered self-assembled monolayer film of an azobenzenealkanethiol on Au(Ill) - Electrochemical properties and structural characterization by synchrotron in-plane X-ray-diffraction, atomic-force microscopy, and surface-enhanced Raman-spectroscopy. J. Am. Chem. Soc. 1995 117, 6071-6082 ... 

Substrates for surface-enhanced Raman scattering (SERS) were prepared by vapor deposition of silver directly onto the surface of porous alumina. Silver nanostructures have been characterized by SEM and UV-Vis absorption. The SERS-activity of the substrates tested with water-soluble cationic Cu-porphyrin as a probe molecule, attained the maximum when Ag mass thickness vtas approximately 60 nm. 

Surface-enhanced Raman scattering (SERS) is a powerful tool for characterization, sensing and quantitation of variety of chemical, environmental and biological analytes at trace concentrations [1]. The considerable enhancement of SERS is attributed to highly concentrated local electric fields in the structures with closely spaced noble metal nanoparticles (NPs). An engineering of novel nanostructures for SERS with advanced properties is of immediate interest for experimentalists. 

A prerequisite for the development indicated above to occur, is a parallel development in instrumentation to facilitate both physical and chemical characterization. TEM and SPM based methods will continue to play a central role in this development, since they possess the required nanometer (and subnanometer) spatial resolution. Optical spectroscopy using reflection adsorption infrared spectroscopy (RAIRS), polarization modulation infrared adsorption reflection spectroscopy (PM-IRRAS), second harmonic generation (SFIG), sum frequency generation (SFG), various in situ X-ray absorption (XAFS) and X-ray diffraction spectroscopies (XRD), and maybe also surface enhanced Raman scattering (SERS), etc., will play an important role when characterizing adsorbates on catalyst surfaces under reaction conditions. Few other methods fulfill the requirements of being able to operate over a wide pressure gap (to several atmospheres) and to be nondestructive. 

Leverette, C.L. and Dluhy, R.A. (2004) Vibrational characterization of a planar-supported model bilayer system utilizing surface-enhanced Raman scattering (SERS) and infrared reflection-absorption spectroscopy (IRRAS). Colloids and Surfaces A, 243, 157-167. 

P. Tessier, S. Christesen, K. Ong, E. Clemente, A. Lenhoff, E. Kaler and O. Velev, On-line spectroscopic characterization of sodium cyanide with nanostructured gold surface-enhanced Raman spectroscopy substrates, Appl. Spectrosc. 56, 1524 (2002). 

F. Inscore, A. Gift, P. Maksymiuk and S. Farquharson, Characterization of chemical warfare G-agent hydrolysis products by surface-enhanced Raman spectroscopy, Proc. SPIE 5585, 46 (2004). 

F. Inscore and S. Farquharson, Surface-enhanced Raman Spectroscopic characterization of sulfur mustard, half-mustard, their hydrolysis products and related mono-sulfides, J. Raman Spectros. (in preparation). 

---