Surface-enhanced IR absorption

Miki A, Ye S, Osawa M. 2002. Surface-enhanced IR absorption on platinum nanoparticles an apphcation to real-time moititoring of electrocatalytic reactions. Chem Commun (14) 1500-1501. 

LC-IR using surface-enhanced IR absorption spectroscopy (SEIRAS) was recently designed in order to develop a highly sensitive and rapid analysis method for polymer additives [506]. The method, which consists of spraying the LC eluents on to a metal film of Ag on a BaF2 substrate, allows an enhancement factor of about 90. 

Comparison of AIREs with the Phenomenon of Surface-Enhanced IR Absorption (SEIRA)... 

Due to the surface sensitivity surface enhanced fluorescence has become particularly popular in the characterisation of thin molecular films, such as Langmuir-Blodgett films and self-assembled biomembranes. Two surface enhanced spectroscopic techniques (surface enhanced IR absorption, SEIRA, and surface enhanced fluorescence, SEF) were recently applied to the study of biomembrane systems by the group of Reiner Salzer [323]. With SEIRA, specific fingerprints of biomolecules could be obtained with a tenfold IR intensity enhancement With SEF signal enhancement factors greater than 100 were obtained. The enhancement factor was very dependent on the properties and structure of the metal clusters used. With the two techniques biomembranes formed from vesicles with embedded nicotinic acetylchoHne receptors were spectroscopically characterized. 

Enhancement of absorption bands in the IR spectra of ultrathin films in the presence of discontinnons (islandlike) nnder- and ovemanolayers of Ag and An was discovered by Hartstein et al. [356] in the early 1980s. Although these researchers believed that they observed an increase in the vCH band intensities for p-nitro-benzoic acid (p-NBA), benzoic acid, and 4-pyridine-COOH films, it was recently shown [350] that the spectra reported are in actual fact due to fully saturated hydrocarbons (possibly vacuum pump oil). In any case, this discovery has stimulated various research activities and led to the development of surface-enhanced IR absorption (SEIRA) spectroscopy. To date, the SEIRA phenomenon has been exploited in chemical [357] and biochemical IR sensors (see [357-360] and literature therein), in studying electrode-electrolyte interfaces [171, 361-365], and in LB films and SAMs [364, 366-370]. Other metals that demonstrate this effect are In [371] and Cu, Pd, Sn, and Pt [372-375]. The metal films can be prepared by conventional metal deposition procedures such as condensation of small amounts of metal vapor on the substrate, spin coating of a colloidal solution, electrochemical [388], or reactive deposition [299] (see also Section 4.10.2). 

A new in situ Fourier transform IR (Fl lR) method, surface-enhanced IR absorption spectroscopy (SEIRAS Osawa 1997), was employed that could observe the surface of the platinum electrode on a silicon prism while electrochemically polarizing it in... 

Fig. 7 Surface-enhanced IR absorption spectroscopy spectra of platinum on silicon in 0.1 mol dm" HCIO at various potentials under N. (dotted line), in 0.1 mol dm" CH5OH + Ommol dm" bpy (dashed line), in Omol dm" CH OH + 0.1 mmol dm" bpy (line), in 0.1 mol dm" CH3OH + 0.1 mmol dm" bpy. Left OH stretching band, right HOH bending band, formate and perchlorate bands. (Reproduced from Shiroishi et al. 2003, copyright the American Chemical Society)...

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