SERRS Raman spectroscopy

The use of surface-enhanced resonance Raman spectroscopy (SERRS) as an identification tool in TLC and HPLC has been investigated in detail. The chemical structures and common names of anionic dyes employed as model compounds are depicted in Fig. 3.88. RP-HPLC separations were performed in an ODS column (100 X 3 mm i.d. particla size 5 pm). The flow rate was 0.7 ml/min and dyes were detected at 500 nm. A heated nitrogen flow (200°C, 3 bar) was employed for spraying the effluent and for evaporating the solvent. Silica and alumina TLC plates were applied as deposition substrates they were moved at a speed of 2 mm/min. Solvents A and B were ammonium acetate-acetic acid buffer (pH = 4.7) containing 25 mM tributylammonium nitrate (TBAN03) and methanol, respectively. The baseline separation of anionic dyes is illustrated in Fig. 3.89. It was established that the limits of identification of the deposited dyes were 10 - 20 ng corresponding to the injected concentrations of 5 - 10 /ig/ml. It was further stated that the combined HPLC-(TLC)-SERRS technique makes possible the safe identification of anionic dyes [150],... 

R.M. Seifar, M.A.F. Altelaar, RJ. Dijkstra, F. Ariese, U.A. Th. Brinkman and C. Gooijer, Surface-enhanced resonance Raman spectroscopy (SERRS) as an identification tool in column liquid chromatography. Anal. Chem., 72 (2000) 5718-5724. 

Certain roughened surfaces (Ag or Au colloids) exhibit another nice intensification of the Raman effect of 103 to 106 by exciting surface plasmons in the colloid particles this is surface-enhanced Raman, first seen by Fleischmann54, and explained by van Duyne.55 Combining resonance and surface-enhanced effects in surface-enhanced resonance Raman spectroscopy (SERRS), the Raman intensity can increase by factors as large as 1012, so that solutions of concentration down to 10 12 M can be detected. 

The classical Raman effect produces only very weak signals. There are two techniques which very successfully enhance this effect. The resonance Raman spectroscopy RRS is making use of the excitation of molecules in a spectral range of electronic absorption. The surface-enhanced Raman spectroscopy SERS employs the influence of small metal particles on the elementary process of Raman scattering. These two techniques may even be combined surface-enhanced resonance Raman effect SERRS. Such spectra are recorded with the same spectrometers as classical Raman spectra, although different conditions of the excitation and special sample techniques are used (Sec. 6.1). 

Since the pioneering work by Cotton et al. on heme proteins (Cotton et al., 1980), surface enhanced resonance Raman spectroscopy (SERRS), Sec. 6.1, has been used to study a large variety of biomolecules, such as retinal proteins (Nabiev et al., 1985), flavoproteins (Coperland et al., 1984 Holt and Cotton, 1987), chlorophylls (Cotton and Van Duyne, 1982 Hildebrandt and Spiro, 1988), and oxyhemoglobins (de Groot and Hesters, 1987). The advantages of this technique include low sample concentration and fluorescence quenching. The main question is whether or not the native structure and function of the molecule is preserved on the metal surface. 

Goulet, P. J. G., Pieczonka, N. P. W., and Aroca, R. F. (2005). Mapping single-molecule SERRS from Langmuir-Blodgett monolayers on nanostructured silver island films. Journal of Raman Spectroscopy 36 574-580. 

Stone N, Faulds K, Graham D, Matousek P (2010) Deep-SERRS demonstration of deep Raman spectroscopy for non-invasive detection of conjugated SERRS nanoparticles buried within 25 mm of mammalian tissue. Anal Chem 82 3969-3973... 

Fundamental questions related to the electronic configuration of the open or colored forms and the number and structures of the photomerocyanine isomers are considered on the basis of the results of continuous-wave (stationary) and time-resolved (picosecond, nanosecond, and millisecond) Raman experiments. For spironaphthoxazine photochromic compounds, the Raman spectra may be attributed to the TTC (trans-trans-cis) isomer having a dominant quinoidal electronic configuration. Surface-enhanced resonance Raman spectroscopy (SERRS) is demonstrated as a new analytical method for the study of the photodegradation process in solution for nitro-BIPS derivatives. The development of this method could lead to the identification of the photoproducts in thin polymer films or sol-gel matrices and ultimately to control of degradation. 

Trace detection and analysis of species at pico- to femtomolar concentrations using surface-enhanced resonance Raman spectroscopy (SERRS). 

The IR spectra of [Ni(R2Me4[18]aneN10)]2+, where R = Me, Et, Pr, benzyl, confirm that all 4 a-di-imine nitrogen atoms are coordinated to Ni.247 SERRS data have been obtained for Ni(P), where P = OEP, TPP, adsorbed on electrochemical interfaces. For Ni(OEP), adsorption appeared to be edge-on, with mem-carbons closest to the surface.248 Raman spectroscopy was used to follow pH-influenced metal-ion coordination changes in NiHb.249 The complexes (49), where M = Pd, Pt, have vC=N at 1647 cm-1 (Pd) or 1639 cm-1 (Pt).250... 

A further resonant contribution to the enhancement is possible when the molecule has an electronic transition in resonance, or dose to resonance, with the exciting laser so that one obtains surface-enhanced resonant Raman scattering or surface-enhanced resonant Raman spectroscopy (SERRS). In these circumstances the resonant enhancement typically contributes an additional factor of between 100 and 1000 to the intensity of the signal and this makes SERRS a particularly attractive approach for analytical apphcations because of its extremely high sensitivity. 

Developments in Raman spectroscopy, with applications for colorants, have included resonance Raman, surface enhanced Raman spectroscopy (SERS), surface enhanced resonance Raman spectroscopy (SERRS) and near-infrared Fourier transform Raman spectroscopy (NIR-FT-Raman), with the latter technique discussed in the next section. 

SERRS Surface-enhanced resonance Raman spectroscopy... 

Because of such complications, the surface-enhanced resonance Raman spectroscopy (SERRS) was developed. As it exploits the best features of both the SERS and the RRE, the resulting enhancement of the Raman signal intensity can be as high as 10 ". Additionally, SERRS spectra resemble regular RRE spectra, which make the former much easier to interpret. 

SURFACE-ENHANCED RESONANCE RAMAN SPECTROSCOPY (SERRS)... 

Silver-overlayer SERRS also has been used to study in situ the redox reactions of methyl viologen (MV) adsorbed on to a p-type InP SC electrode [42]. These experiments are related to earlier time-resolved resonance Raman spectroscopy (TR3S) work on electron transfer reactions at the surfaces of photoexcited semiconductor colloids (TiOa and CdS) involving... 

SERRS Surface Enhanced Resonance Raman Spectroscopy... 

Surface Enhanced Raman Scattering of Biomolecules Table 5. Resonance Raman spectroscopy of biological chromophores (SERRS studies are underlined)... 

In a study of phenazine adsorbed on a silver electrode that employed both SERS and SEHRS, the electroreduction product of phenazine and the reduction intermediates could be identified [499]. In a comparative study with SERRS and resonantly enhanced hyper-Raman spectroscopy SERHRS, several dyes adsorbed on a roughened silver electrode were investigated [500]. According to the results, the efficiency... 

These spectra were obtained with a smooth, polished surface. Thus no surface enhancement was effective. The molecules under investigation can alternatively be deposited onto roughened surfaces and the obtained spectra show a combination of surface and resonance enhancement. The method is called surface enhanced resonance Raman spectroscopy (SERRS). 

RAS Raman spectroscopy [also NR(S)], see also DESERS,SERRS, SERS, SRS, SRRS, SUERS... 

NOj(N02/N204) gas and the effect of gas adsorption was monitored using visible and infrared spectroscopy the high sensitivity surface-enhanced resonance-Raman spectroscopy (SERRS) allowed to observe the reversible chemical absorption of NO2 on a monomolecular LB layer of PrPc2 and PrPc. ... 

Figures 5-7 contain examples of use of oxides for Enhanced Raman Spectroscopy using unconventional substrates. Scandium (II) oxide and tin (IV) oxides were used as proof of concept experiment. Oxides used are semiconductors and in these cases signal enhancement was significant. The ERS spectra obtained using oxides to enhance Raman signals are quite different than ordinary SERS or Surface Enhanced Resonance Scattering (SERRS).

While the redox chemistry of metal- and flavin-based cofactors may be readily detected by voltammetry, that associated with thiol-disulfides and amino acids is not. It is also important to be aware that voltammetry by itself provides no direct insight into the chemical identity of the redox couple. This can be overcome by using electrodes that allow for simultaneous spectroscopic and voltammetric analysis of adsorbed proteins. Examples include Ag electrodes that allow for surface-enhanced resonance Raman spectroscopy (SERRS) and mesoporous nanocrystalline Sn02 electrodes that allow for electronic absorption or magnetic circular dichro-ism spectroscopies [3]. Another consideration is the need for a redox center to be positioned within ca. 14 A of the electrode, and so the surface of the protein, for facile interfacial electron exchange. As a consequence, proteins with only buried redox centers are not routinely addressed by direct electrochemical methods. 

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