Surface-enhanced infrared absorption SEIRA spectroscopy

The phenomenon of surface-enhanced infrared absorption (SEIRA) spectroscopy involves the intensity enhancement of vibrational bands of adsorbates that usually bond through contain carboxylic acid or thiol groups onto thin nanoparticulate metallic films that have been deposited on an appropriate substrate. SEIRA spectra obey the surface selection rule in the same way as reflection-absorption spectra of thin films on smooth metal substrates. When the metal nanoparticles become in close contact, i.e., start to exceed the percolation limit, the bands in the adsorbate spectra start to assume a dispersive shape. Unlike surface-enhanced Raman scattering, which is usually only observed with silver, gold and, albeit less frequently, copper, SEIRA is observed with most metals, including platinum and even zinc. The mechanism of SEIRA is still being discussed but the enhancement and shape of the bands is best modeled by the Bruggeman representation of effective medium theory with plasmonic mechanism pla dng a relatively minor role. At the end of this report, three applications of SEIRA, namely spectroelectrochemical measurements, the fabrication of sensors, and biochemical applications, are discussed. 

Thin film of metal clusters enable other types of surface enhancement, one of these is the surface enhanced infrared absorption (SEIRA) spectroscopy. The enhancement is an addition of electromagnetic field effects and chemical effects, therefore highly dependent on the distance to the cluster layer and on the nano-structure of the cluster layer. In fact most studies done point out that the effect is very short ranged and only applicable to the first monolayer adsorbed to the surface. Compared to standard infrared spectroscopy and Surface enhanced Raman scattering SEIRA has a remarkable signal to noise ratio and the... 

Alternatively, various analytical methods based on SPR phenomenon have been developed, including surface plasmon field-enhanced Raman scattering (SERS) [7], surface plasmon field-enhanced fluorescence spectroscopy (SPFS) [8-11], surface enhanced second harmonic generation (SHG) [12], surface enhanced infrared absorption (SEIRA) [13], surface plasmon field-enhanced diffraction spectroscopy (SPDS) [14-18], Most of these methods take advantage of the greatly enhanced electromagnetic field of surface plasmon waves, in order to excite a chromophoric molecule, e.g., a Raman molecule or a fluorescent dye. Therefore, a better sensitivity is expected. 

Furthermore, it is possible to increase the sensitivity of the IR technique, and thus the probability of detecting transient surface species characterized by (very) low absorption coefficients (such as the intermediate species present during the first steps of the polymerization reaction on the Phillips catalyst) by exploiting the surface-enhanced infrared absorption (SEIRA) effect. It is known that molecules adsorbed on metal island films or particles exhibit 10-1000 times more intense infrared absorption than would be expected from conventional measurements without the metal (253-256). The possibility of performing SEIRA spectroscopy should therefore be expected to provide an opportunity to better investigate the nature of the intermediate species, not only for ethene polymerization on Cr(II)/ Si02, but for other reactions on solid catalysts. 

Surface enhanced infrared absorption (SEIRA) has been observed in external reflection spectroscopy [185], for further details, see Sect. 5.2.5. 

Two of the many enhanced optical phenomena in surface-enhanced spectroscopy are surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA). These two phenomena and now analytical techniques can be described as a new branch of vibrational spectroscopy that deals with the spectra of molecules on specially fabricated nanostructures with the... 

Finally, it is evident that SERS should be considered from a wider perspective and comparing the performance of SERS with other techniques can always be useful. For example, fluorescence microscopy and spectroscopy are extremely sensitive and widely used techniques in many areas of the life sciences. Further development and expanding of other surface-enhanced spectroscopic techniques such as surface-enhanced infrared absorption (SEIRA), surface-enhanced fluorescence (SEF) and tip-enhanced Raman scattering (TERS) are also highly desirable. It is highly appreciable so that these techniques will help to refine information obtained by SERS in many bioanalytical, biomolecular and medical studies. 

A related effect has been described for IR spectroscopy - Surface Enhanced Infrared Absorption spectroscopy (SEIRA). However, as the enhancement factors are significantly lower than for SERS and both the required metal particle size and the activation distance between the target molecule and the particle are more than one order of magnitude smaller, no practically applicable SEIRA sensors have been demonstrated up to now. 

Surface Enhanced Infrared Absorption Spectroscopy (SEIRAS)... 

SEIRAS Surface enhanced infrared absorption spectroscopy... 

These ions undergo only weak perturbations upon adsorption. Thus, it can be difficult to discriminate species in solution, or in the diffuse doublelayer, from ions at the electrode surface [54]. Better selectivity for adsorbed electrolyte anions has been achieved through use of the surface-enhanced infrared absorption spectroscopy (SEIRAS) technique [22, 54, 89, 90]. Methods for the preparation of quasi-single crystalline thin films are enabling the study of electrolyte adsorption on structurally well-defined surface sites by SEIRAS [22, 89,... 

Over recent years, internal reflectance infrared studies have tended to concentrate on the study of relatively thick films of conducting polymers or layers, (see, for example, the work of Pham and coworkers [49, 50], or Kvarn-strom, Nauer, Neugebauer and coworkers [51-54]) in which sensitivity was not a particular problem, or on the semiconductor-electrolyte interface, (see the work of Chazalviel and coworkers [35, 40, 41]), in which the SPP excitation approach is not appropriate. However, interest has focused again on this phenomenon with the surface-enhanced infrared absorption spectroscopy (SEIRAS) studies of Osawa and coworkers [19, 26, 27, 46, 55, 56], who have combined the application of the Kretschmann configuration with step-scan FTIR spectroscopy to study fast, reversible electrochemical processes on timescales down to microseconds [26, 46, 57-60]. 

Osawa, M. (1997). Dynamic processes in electrochemical reactions studied by surface-enhanced infrared absorption spectroscopy (SEIRAS). Bull. Chem. Soc. Jpn 70, 2861. 

SERS (Surface Enhanced Raman Scattering) and, more recently, SEIRA (Surface Enhanced Infrared Absorption) spectroscopies have rapidly expanded their field of applications. These techniques are based on the use of noble metal nanoparticles (NPs) supporting Localized Surface Plasmons (LSP). They are extremely attractive due to unique high sensitivity and their potential for molecule-specific sensing technologies utilizing vibrational signatures 1,2). 

Okada, T, Satou, H. emd Yuasa, (20(B) M. Effects of Additives on Oxygen Reduction Kinetics at the Interface between Platinum and Perfluorinated lonomer. Langmuir 19, 2325-2332 Osawa, M. (1997) Dynamic Processes in Electrochemiceil Reactions Studied by Surface-Enhanced Infrared Absorption Spectroscopy (SEIRAS). Bull. Chem. Soc. Jpn. 70, 2681-2880 Shiroishi, H., Ayato, Y, Kunimatsu, K. and Okada, T. (2004) Effect of Additives on Electrochemical Reduction of Oxygen in the Presence of Methanol. Chemistry Lett. 33,792-793 Shiroishi, H., Ayato, Y., Okada, T. and Kunimatsu, K. (2(X)5) Mechanism of Selective Oxygen Reduction on Platinum by 2-2 -Bipyridine in the Presence of Methanol. Langmuir 21, 3037-3043... 

Leverette, C.L, Jacobs, S.A., Shanmukh, S., Chaney, S.B Dluhy, R.A. and Zhao, Y,-P, (2006) Aligned silver nanorod arrays as substrates for surface-enhanced infrared absorption spectroscopy (SEIRA). Applied Spectroscopy, 60, 906-13. 

Figure 6.16 Attenuated total reflection surface enhanced infrared reflection absorption spectroscopy (ATR-SEIRAS) spectra for the oxidation of 0.1 M HCOOH in 0.5 M H2SO4 on a polycrystaUine electrode. The bands at 2055 -2075 and 1800-1850 cm are assigned to linear- and bridge-bonded CO, whereas the band at 1323 cm corresponds to adsorbed formate. (Reproduced from Samjeske et al. [2006].)...

Recently, Shao et al. proposed superoxide (O2) formation as the first step of the ORR on Pt films in alkaline solution (NaC104 with pH=ll) by analyzing spectral data of surface-enhanced infrared reflection absorption spectroscopy with attenuated total reflection (ATR-SEIRAS). This was fuller supported by Zhang and Anderson, who performed DFT cluster calculations for the ORR on Pt(lll), Pt(lOO), and umeconstracted Pt(llO). They... 

We have organized the work herein as follows In Sect. 2 we will discuss briefly two typical electrochemical substrates, Au(l 11) and Au(lOO) in 0.05 M H2SO4, employing in-situ scanning tunnehng microscopy (STM) and surface-enhanced infrared refiection/absorption spectroscopy (ATR-SEIRAS). Self-assembled physisorbed adlayers of various hydrogen-bonded carboxyhc acids will be described in Sect. 3. Then we will focus on selected properties of chemisorbed self-assembled aromatic adlayers based on experiments with... 

The structure and orientation of water molecules on quasi single-crystalline Au(lll -20 nm) thin film electrodes in contact with aqueous sulfuric acid solution were studied by surface-enhanced infrared reflection absorption spectroscopy employing an ATR configuration (ATR-SEIRAS) [22,31]. The spectrum of interfacial water is strongly dependent on electrode potential, ionic strength and pH. Figure 4A shows a series of SEIRA spectra recorded within the potential range of an ideally polarizable Au(lll) electrode in... 

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