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Prof. P. A. Christensen

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Updated: 28 Jan 09

 

In-situ FTIR spectroscopy: Introduction

In-situ electrochemical Fourier Transform InfraRed Spectroscopy, (FTIR), is one of several in-situ spectroscopic techniques available in the group, and has been developed and updated over a number of years. Currently, I have three dedicated systems based upon Varian FTS-7000, FTS-60 and FTS-6000 spectrometers, interfaced to dedicated electrochemical interfaces, which control both the electrochemistry in the spectroelectrochemical cell and the data collection/manipulation. For a Powerpoint presentation covering the basics of in-situ FTIR click here.

The advent of affordable, research grade FTIR spectrometers was followed by a rapid increase in the amount and diversity of in-situ electrochemical IR studies, essentially as a result of their inherently high sensitivity, and rapid spectral collection times. As well as effectively solving the sensitivity problems associated with collecting IR spectra from (sub) monolayer adsorbates through water, FTIR spectrometers facilitated the application of simple data collection and manipulation methods, and consequently greatly increased the experimental protocols that could be employed.

In essence, the routine use of FTIR spectrometers has meant that in-situ IR spectroscopic studies requiring high sensitivity, such as the study of adsorbed species, were no longer limited to the fast, reversible electrochemical systems dictated by lock-in detection techniques such as Electrochemically Modulated Infra Red Spectroscopy, (EMIRS); IR spectra could be collected during a slow linear voltammetric sweep, during a series of potential steps to higher or lower potentials, or as a function of time after a single potential step.

More recently, the advent of step-scan FTIR spectrometers have heralded a return to the study of reversible systems, but at much faster timescales, ie. on the order of ms; see the work of Osawa and colleagues( M. Osawa et. al., Langmuir, 10 (1994) 640). The operation of FTIR spectrometers, and their "Advantages" have been described in detail elsewhere, (see, for example, P. A. Christensen and A. Hamnett, Comprehensive Chemical Kinetics 29 (1989) 1, and P. R. Griffiths and J. A. de Haseth, "Fourier Transform Infrared Spectrometry"; John Wiley & Sons: New York, 1986; Vol. 83, pp 254.).

Briefly, the heart of an FTIR spectrometer is the Michaelson Interferometer, MI see fig. 1 on the next page.

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