Techniques for SERS

To obtain surface enhanced Raman spectra from adsorbates, special sample techniques are required to produce surface roughness or small clusters either isolated in solution or as powders at surfaces. Several techniques have been described in detail in the literature (see for example Cooney et al., 1982 Cotton, 1988). 

In the following we discuss shortly only a few of the most common types of substrates. For details we refer to the reviews cited above or to original papers published in journals. 

In order to investigate molecules adsorbed at the solid-liquid interface roughened electrode surfaces or metal colloids in solution (sols) are prepared. For investigations of the solid-gas or solid-vapour interface several methods are available to produce metal island films on SERS-active substrates. 

Electrodes. The first observations of SERS were made from species on silver electrodes. An essential prerequisite for a strong SERS signal from molecules adsorbed on the electrode, surface roughness, is obtained by running electrochemical oxidation-reduction cycles (ORC) (Chang and Laube, 1984 Koglin and Sequaris, 1986 Roth et al., 1993). During the oxidation half cycle a metal salt, usually a halide, is formed at the electrode surface  

When reduced, the liberated metal does not redeposit uniformly over the electrode surface, but instead forms clusters of the metal at the surface  

---

Here, the use of FPro systems as a temporary protection technique for Ser-, Thr-, or Cys-containing peptides proved to strongly improve the yields and purity of otherwise difficult sequences as shown by a steadily increasing number of comparative studies [156-162,168-181]. Most notably, the use of C2 dimethyl substituted FPro building blocks [168-172] results in the formation of a cis-amide bond in the regular peptide backbone ( kink conformation ), thus preventing jS-sheet... 

An extraordinarily simple and low-cost analytical technique for SERS dmg detection using Ag NPs printed onto paper by a commercial inkjet printer is illustrated in Fig. 4.6 (Yu and White 2013). Ink was formed by standard... 

Hei.ser, T., 1990. Amino acid chromatography The best technique for. student 2hs,. Journal of Chemical Education 67 964-966. 

Snyder, A. R Electrospray A popular ionization technique for mass spectrometry. ACS Symp. Ser. 1996, 619,1-20. 

Gibson, B. W. Phillips, N. J. John, C. M. Melaugh, W. Lipooligosaccharides in pathogenic Haemophilus and Neisseria species—Mass spectrometric techniques for identification and characterization. ACS Sympo. Ser. 1994,541,185-202. 

Whilst SERS represents a potentially extremely sensitive technique for the study of adsorbed species in electrochemistry and an enormous number of... 

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. 

The extremely small cross sections for conventional Raman scattering, typically 10 111 to 10-25 cm2/molecule has in the past precluded the use of this technique for single-molecule detection and identification. Until recently, optical trace detection with single molecule sensitivity has been achieved mainly using laser-induced fluorescence [14], The fluorescence method provides ultrahigh sensitivity, but the amount of molecular information, particularly at room temperature, is very limited. Therefore, about 50 years after the discovery of the Raman effect, the novel phenomenon of dramatic Raman signal enhancement from molecules assembled on metallic nanostructures, known as surface-enhanced Raman spectroscopy or SERS, has led to ultrasensitive single-molecule detection. 

Chubb, J.N., and Butterworth, G.J., Instrumentation and techniques for monitoring and assessing electrostatic ignition hazards, Inst. Phys. Conf. Ser. No. 48, p. 88, 1979. 

Surface-Enhanced Raman Spectroscopy (SERS) SERS is a technique for increasing the sensitivity of a Raman instrument. This module explores its application to the detection of chemicals indicative of brain injury. 

Verity PG, Smetacek V (1996) Organism life cycles, predation, and the structure of marine pelagic ecosystems. Mar Ecol Prog Ser 130 277-293 Vos P, Hogers R, Bleeker M, Reijans M, Vandelee T, Hornes M, Frijters A, Pot J, Peleman J, Kuiper M, Zabeau M (1995) AFLP—a new technique for DNA fingerprinting. Nucleic Acids Res 23 4407-4414... 

Snyder AP (1995) Electrospray a popular ionization technique for mass spectrometry. In Snyder AP (1995) (ed) Biochemical and biotechnological applications of electrospray ionization mass spectrometry. Acs Symp Ser, vol 619, p 1... 

Kogelschatz U (1993) UV Production in Dielectric Barrier Discharges for Pollution Control, in Penetrante BM, Schultheis S E (eds.) Non-thermal Plasma Techniques for Pollution Control, NATO ASI Ser. G 34, Part B 339-353. 

Christen.sen PA, Hamnett A (1989) In-situ infrared studies of the electrode-electrolyte interface. In Compton RG, Hamnett A (eds) New Techniques for the Study of Electrodes and their Reactions. Elsevier. Amsterdam Oxford New York, p 1 Christie DA, McCreery RL (1990) Appl Spectrosc 44 1229 Chu CW, Gao L, Chen F, Huang ZJ, Meng RL (1993) Nature 365 326 Chu HT et al (1979) Adv Chem Ser 174 87 Chung Y, Ziegler LD (1988) J Chem Phys 88 7287... 

Electrochemical Interfaces Modern Techniques for in-situ Interface Characterisation, H.D. Abrufta, E., VCH, New York, (1991). (X-ray, SERS, nonlinear optics, IR Mdssbauer, etc.)... 

We have shown that SERS-encoded particles have been established as a solid and reliable analytical technique for the detection in extremely low amounts of a wide variety of bioanalytes. SERS-encoded particles for indirect detection and labeling can be implemented on chip or even inside living cells, tissues, or a variety of microorganisms. 

Cicada Wings for SERS and a Simple Lithographic Technique for Replicating Their Nanostructure... 

The optical fibers were loaded in an array of up to 40 fibers each placed in an individual U-shaped groove cut into an aluminum block, shown in Fig. 4.13. This technique allowed multiple fibers to be imprinted with the cicada wing mould in a simple and rapid manner that was not critically reliant upon alignment. The resolution obtained with this method was better than 15 nm, producing bidirectional optical fiber prober for SERS with enhancement factors only slightly less than those obtained from the original structures on the cicada wings. 

High levels of SERS activity can be expected if nanoparticle substrates were prepared by colloidal chemical methods because colloidal particles tend to aggregation, thus forming the narrow interparticle spacings needed for plasmon coupling. A traditional technique for the preparation of silver colloids is the sol formation according to Lee et al. [17]. 

---