Surface-enhanced Raman Spectroscopy Study Research Articles

Surface Enhanced Raman Spectroscopy Study of the Galvanostatic Reduction of the Passive Film on Iron

Surface enhanced Raman (SER) spectra were acquired continuously with time during the galvanostatic reductive dissolution of the passive film grown on iron in borate buffer (pH 8.4) by anodic polarization at one of three different potentials, +1000, +600, and 0 mV (SCE). Complementary measurements of the SER spectra of the passive film were made during the formation of the film by galvanostatic anodic polarization. The results indicate that the passive film consists of a layered structure with at least two components. The inner layer is most likely and the outer layer is primarily an Fe(III) species with an SER spectrum that is characterized by an intense, broad peak centered in the range . The outer layer may also contain that is associated with an SER spectroscopy peak at . © 1999 The Electrochemical Society. All rights reserved.

Surface-enhanced hyper-Raman spectroscopy (SEHRS) and surface-enhanced Raman spectroscopy (SERS) studies of pyrazine and pyridine adsorbed on silver electrodes

Both surface-enhanced hyper-Raman spectroscopy (SEHRS) and surface-enhanced Raman spectroscopy (SERS) spectra of pyrazine and pyridine adsorbed on silver electrode surfaces were obtained at different potentials. Although there is a relaxation of the symmetry selection rule to a certain extent, it is demonstrated experimentally here that the SEHR spectrum for a centrosymmetric molecule (pyrazine) shows some new vibrational bands and significant relative intensity changes compared with its SER spectrum. By contrast, the SEHR spectrum for a non-centrosymmetric molecule (pyridine) resembles its SER spectrum and shows the absence of new vibrational bands. Our results also show that SEHRS is more sensitive to the interaction between the adsorbate and the substrate than SERS.

Extending surface-enhanced Raman spectroscopic studies on water at gold electrodes

Surface-enhanced Raman scattering (SERS) of water molecules from gold electrodes is reported for the first time. The metal substrate effect on the SERS active water is investigated by comparison of gold with silver in 3 M KCl. The SERS spectra of water recorded at various electrode potentials are significantly different for the two metals. The SERS active surface structure of gold is much more stable and there may exist two types of the surface structure for gold at 0.3 and −0.3 V, respectively. The results indicate that the electromagnetic (EM) and chemical enhancement mechanisms operate simultaneously.

Surface-enhanced resonance Raman spectroscopic studies of the PbII complex of 1-(2-pyridylazo)-2-naphthol adsorbed on Ag Sol

The resonance Raman (RR) and surface-enhanced resonance Raman (SERRS) spectra of the PbII complex of 1-(2-pyridylazo)-2-naphthol, Pb(PAN)2, are reported and assigned, and the nature of the adsorbed species determined. There is clear evidence for chemisorption of Pb(PAN2) on silver, which gives rise to substantial alteration of the Raman spectrum. Comparison of the variation of Raman intensities with excitation wavelengths for the RR and SERRS spectra indicates that there is a contribution to the surface-enhancement from both the chemical and electromagnetic SERS mechanisms. The dependence of the Raman spectrum on Pb(PAN)2 concentration and co-adsorbed Cl– is investigated. There is a linear relationship between adsorbate concentration and SERRS intensity, enabling the technique to be used for the quantitative determination of Pb(PAN)2 down to ca. 1 ppb.

Waveguide Surface-Enhanced Resonance Raman Spectroscopy of Ru(bpy)32+

Surface-enhanced resonance Raman spectroscopy (SERRS) has been successfully combined with an optical waveguide in this Ru(bpy) 3 2+ /silver sol/PVA study in which detection of ∼40 pg of Ru(bpy) 3 2+ has been achieved. These results demonstrate that waveguide SERRS is a promising technique for the study of surface species and of interactions between a host matrix and embedded guest molecules. The waveguide SERRS technique described in this work is the first reported surface-enhanced Raman spectroscopy (SERS) study of an adsorbate trapped in a polymer matrix

Surface-enhanced Raman spectroscopic studies on structural dynamics of coadsorption of thiourea and ClO 4− at Ag electrodes

Time-resolved surface-enhanced Raman spectroscopy (TRSERS) and potential-averaged surface-enhanced Raman spectroscopy (PASERS) have been combined with the potential step method to study thiourea (TU) and ClO 4− coadsorbed at Ag electrodes. The SERS intensity—time profiles show that when a potential step is applied, the response rate of the SERS intensity depends significantly on the stepping direction. The slow surface process may involve a rearrangement of the coadsorbed layer which has two distinct structures at the two potentials stepped. Furthermore, the intensities of different SERS bands for the adsorbed TU have surprisingly different response rates to the potential step. This reveals that for detailed structural dynamic studies of some complicated electrosorption process it may be necessary to focus individually on various groups (or intramolecular bondings) of the adsorbate rather than considering the whole adsorbate as rigid, as is usually done.

Characterization of alkali-metal sols in diethyl ether. Visible extinction and surface-enhanced Raman spectra

Colloidal suspensions of Na, K, Rb, and Cs have been prepared in diethyl ether. The visible extinction spectra of each are compared with results of theoretical Mie-scattering spectra, calculated using a variety of optical constant data sets. Comparison of the experimental extinction spectra to the theoretical spectra demonstrates that fresh sols of Na, K and Rb contain small metal particles with diameters suitable for surface-enhanced Raman (SER) spectroscopic studies. Fresh Cs colloids, reported for the first time, show signs of particle aggregation in long strings. Raman spectra of Na, K and Rb colloids are presented in the region between 150 and 700 cm −1. We find that Na colloids display two broad SER features at 290 and 530 cm −1, K colloids display two SER features at 220 and 480 cm −1, and Rb colloids display one band at 215 cm −1. The lower-frequency bands for Na and K sols and the 215 cm −1 band of Rb sols may be due to lattice modes of amorphous alkali-metal hydroxides on the metal surfaces. The two higher-frequency bands at 480 and 530 cm −1 remain unassigned.

A comparative study of the inhibition effects of benzotriazole and 6-aniline-1,3,5-triazine-2,4-dithiol monosodium salt on the corrosion of copper by potentiodynamic polarization, AC impedance and surface-enhanced Raman spectroscopic techniques

The inhibition effects of benzotriazole (BTA) and 6-aniline-1,3,5-triazine-2,4-dithiol (ATD) monosodium salt on copper corrosion have been studied by the potentiodynamic polarization, AC impedance and surface-enhanced Raman spectroscopic techniques. The polarization resistance R p increases with the concentration of either BTA or ATD. From the plots of the phase shift θ versus logarithm of the frequency, it is found that θ is close to 90° after the copper electrode is immersed for a long period of time in BTA-containing solution which indicates the behavior of an ideal capacitor. In ATD-containing solutions, θ is close to 45 ° which shows the appearance of a Warburg impedance for a diffusion process. Surface-enhanced Raman spectroscopic studies of the competitive adsorption of BTA and ATD on copper surfaces indicate that BTA adsorbs better than ATD. Based on these results, it is concluded that the inhibition action of BTA is better than that of ATD.

A surface enhanced Raman spectroscopy study of the corrosion-inhibiting properties of benzimidazole and benzotriazole on copper

Surface enhanced Raman spectra of benzimidazole and benzotriazole on copper have been obtained. A characteristic imidazole ring stretching mode located near 780 cm{sup {minus}1} shows splitting in the benzotriazole-copper surface comlex. This splitting is not observed in benzimidazole. The spectrum of benzotriazole is interpreted as two distinct benzotriazole species on the surface. On the basis of this information a new structure for benzimidazole and benzotriazole on copper surfaces is proposed.

Functional activity of hemoglobins adsorbed on colloidal silver: a surface-enhanced resonance Raman spectroscopy study

Functional activity of hemoglobins adsorbed on colloidal silver: a surface-enhanced resonance Raman spectroscopy study

The chromophore-binding site of bacteriorhodopsin. Resonance Raman and surface-enhanced resonance Raman spectroscopy and quantum chemical study

Surface-enhanced Raman spectra of membrane protein, located in native mem brane, bacteriorhodopsin, adsorbed by silver electrodes and hydrosols have been obtained for the first time. The distance between the retinal Schiff’s base and the external side of purple membrane of Halobacteriim halobiim was shown to be 6–9 A.