Cell, spectroelectrochemical spectroscopy

Vibrational spectroelectrochemical techniques, particularly Fourier transform infrared (FTIR), with the advent of less-expensive and more sensitive spectrometers, have enjoyed a great increase in popularity over the last few years. The advantages over UV-vis spectroscopy include greater specificity and enhanced information content. An IR OTTLE transmission cell with IR-transparent windows can be built by modifying a commercial liquid cell. Raman spectroscopy is also very easily carried out with an OTTLE cell, but a flow cell is more useful for SERS studies of adsorption, since the solution can be replaced without disturbing the optical alignment. 

The chaimel-flow electrode has often been employed for analytical or detection purposes as it can easily be inserted in a flow cell, but it has also found use in the investigation of the kinetics of complex electrode reactions. In addition, chaimel-flow cells are immediately compatible with spectroelectrochemical methods, such as UV/VIS and ESR spectroscopy, pennitting detection of intennediates and products of electrolytic reactions. UV-VIS and infrared measurements have, for example, been made possible by constructing the cell from optically transparent materials. 

Infrared spectroelectrochemical methods, particularly those based on Fourier transform infrared (FTIR) spectroscopy can provide structural information that UV-visible absorbance techniques do not. FTIR spectroelectrochemistry has thus been fruitful in the characterization of reactions occurring on electrode surfaces. The technique requires very thin cells to overcome solvent absorption problems. 

Figure 12.1 Schematic of the spectroelectrochemistry apparatus at the University of Dlinois. The thin-layer spectroelectrochemical cell (TLE cell) has a 25 p.m thick spacer between the electrode and window to control the electrolyte layer thickness and allow for reproducible refilbng of the gap. The broadband infrared (BBIR) and narrowband visible (NBVIS) pulses used for BB-SFG spectroscopy are generated by a femtosecond laser (see Fig. 12.3). Voltammetric and spectrometric data are acquired simultaneously.

Figure 9.12 Spectroelectrochemical cell for Fourier-transform infrared reflection absorption spectroscopy (FTIRRAS). (A) Cell components showing Teflon bar for controlling the sample path length (B) retroreflection absorption optics for use with this cell. [From I.T. Bae, X. Xing, E.B. Yeager, and D. Scherson, Anal. Chem. 61 1164 (1989). Copyright 1989 American Chemical Society.]...

Figure 9.13 Spectroelectrochemical cell for Raman spectroscopy studies using electrode emersion. (A) Top view of cell, micrometer adjusts cell path length (B) front view with 90° rotation of reference electrode position. [From J.E. Pemberton and R.L. Sobocinski, J. Electroanal. Chern. 575 157 (1991). Copyright 1991 Elsevier Sequoia S.A., Lausanne.]...

Spectroelectrochemical cells that permit redox titrations of precious biological samples, require exclusion of oxygen, and allow acquisition of data from multiple spectroscopic domains have been described. A recent example of these cell designs combines electron paramagnetic resonance spectroscopy with UV-visible absorption spectroscopy [71] for studies of flavoproteins. 

A vacuum spectroelectrochemical cell that also contains an optically transparent thin-layer electrode (OTTLE) is shown in Figures 18.16 and 18.17. The cell can function either as a spectroelectrochemical cell employing an OTTLE or as an electrochemical cell for voltammetric measurements. This low-volume cell is useful for UV/Vis spectral studies in nonaqueous solvents when the reduction product is sensitive to traces of molecular oxygen present in the solvent. The cell is physically small enough to fit inside the sample compartment of the spectrophotometer. The performance of such a cell was evaluated from visible spectroscopy and coulometry of methyl viologen in propylene carbonate [45]. 

Nuclear magnetic resonance (NMR) spectroscopy — Nuclear magnetic resonance (NMR) spectroscopy of atoms having a nonzero spin (like, e.g., H, 13C) is an extremely powerful tool in structural investigations in organic and inorganic chemistry. Beyond structural studies atoms observable with NMR can also be used as probes of their environment. Thus NMR may be employed for in situ spectroelectrochemical studies [i]. Cell designs for in situ NMR spectroscopy with electrochemical cells are scant. Because of the low sensi-... 

Figure 45. Examples of spectroelectrochemical cells for use in transmission spectroscopy (top) and internal reflectance spectroscopy (bottom). (From Ref. 281.)...

Fig. 5.15. Schematics of spectroelectrochemical cells for electroreflectance spectroscopy. Top Arrangement for measurements at various angles of incidence bottom Cell for measurement with electrodes in the dipping technique...

Figure 5 presents the experimental setup of in situ electrochemical Raman spectroscopy. The instrument for in situ Raman spectroscopic studies of electrochemical systems includes a laser as the excitation source, a Raman spectrometer, a personal computer for control of the Raman spectrometer, data acquisition and manipulation, as well as a plotter or printer for data output, a potentiostat /galvanostat and possibly a wave function generator for generation of various kinds of po-tential/current control over the electrode, and the spectroelectrochemical cell. Details of electrochemical instrumentation were given in Chapter 1.2 see this chapter for various definitions, including WE... 

One organic redox system that we have studied by transmission spectroelectrochemical measurements is chlorpromazine (CPZ) [118]. The electrochemistry and spectroscopy of CPZ have been investigated extensively over the years [22,30,179]. Figure 24A shows a cyclic voltammetric (background corrected) i-E curve for 100 gM CPZ + 10 mM HCIO4. The measurement was made in a specially designed, thin-layer electrochemical cell with a path length of 150 gm and a cell volume of 5 gL [118]. The scan... 

Fig. 5. Single beam arrangement for electroreflectance spectroscopy. L xenon lamp, FL optical filter, M monochromator, S slit, C spectroelectrochemical cell, PS potentiostat, FG function generator, OSC oscillator, HV high-voltage power supply, PM photomultiplier, FB feedback circuit, NF noise filter, LPF low-pass filter, LIA lock-in-amplifier, PC personal computer.

Flowers PA, Strickland JC (2010) Easily constructed microscale spectroelectrochemical cell. Spectroscopy Lett 43 528-533... 

Figure 14.11 Fiber optic spectroelectrochemical arrangement for electronic spectroscopy. A conventional electrochemical ceU is combined with a fiber optic spectrometer in which the optical fiber is directed in front of the working electrode at the bottom of the cell.

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