Optically-transparent thin-layer electrochemical cell

Fig. 6. UV-visible spectra of 0.05 mM oxidized and reduced recombinant Rhodnius NP3 (a) at pH 7.5 without ligand (b) at pH 7.5 bound to NO (c) at pH 5.5 bound to NO. In each case, the spectrum of the oxidized nitrophorin is represented by a solid line and the reduced by a dashed line. Spectra were recorded in an optically transparent thin-layer electrochemical cell of approximate window thickness 0.05 mm. To obtain the fully oxidized and reduced spectra, potentials (vs Ag/AgCl) were applied until no change in optical spectrum occurred, of -1-600 and —400 mV, respectively (a), -1-200 and —400 mV, respectively (b), and 0 and -280mV, respectively (c).

Figure 9.9 Assembly of sandwich-type optically transparent thin-layer electrochemical cell, a, Glass or quartz plates b, adhesive Teflon tape spacers c, minigrid working electrode d, metal thin-film working electrode, which may be used in place of (c) e, platinum wire auxiliary electrode f, silver-silver chloride reference electrode g, sample solution h, sample cup. [Adapted with permission from T.P. DeAngelis and W.R. Heineman, J. Chem. Educ. 53 594 (1976), Copyright 1976 American Chemical Society.]...

The question of whether electrons added to a complex ion become localized or delocalized is important, not only for the type of complex mentioned above, but also for much wider ranges of complexes. For such studies the use of an OTTLE (optically transparent thin layer electrochemical) cell is most appropriate... 

While the redox titration method is potentiometric, the spectroelectrochemistry method is potentiostatic [99]. In this method, the protein solution is introduced into an optically transparent thin layer electrochemical cell. The potential of the transparent electrode is held constant until the ratio of the oxidized to reduced forms of the protein attains equilibrium, according to the Nemst equation. The oxidation-reduction state of the protein is determined by directly measuring the spectra through the tranparent electrode. In this method, as in the redox titration method, the spectral characterization of redox species is required. A series of potentials are sequentially potentiostated so that different oxidized/reduced ratios are obtained. The data is then adjusted to the Nemst equation in order to calculate the standard redox potential of the proteic species. Errors in redox potentials estimated with this method may be in the order of 3 mV. 

Heineman WR, Norris BJ, Goelz JF (1975) Measurement of enzyme H° values by optically transparent thin layer electrochemical cells. Anal Chem 47 79-84... 

OTTLE cell Optically transparent thin-layer electrochemical cell... 

Fig. I, Optically transparent thin-layer electrochemical cell shown in (A) front view and (B) side view, a, Point of suction application to change solution b. Teflon tape spacers c, microscope slides (1x3 in.) d, solution e, transparent gold minigrid electrode f, optical path g, reference and auxiliary electrodes h, solution cup. Epoxy is used to hold the cell together.

To obtain satisfactory results by the OTTLSET, the design of the optically transparent thin-layer electrochemical cell (OTTLEC) is very important. The first OTTLEC was constructed by Murray et al in 1967. Figure 1 shows the structure of this type of cell which contains a gold... 

Figure 7. Small-volume optically transparent thin layer electrochemical cell. (A) Quartz cover plate, (B) Teflon spacer, (C) gold minigrid optically transparent electrode, (D) quartz disc, (E) plastic body, (F) inlet syringe port, (G) Pt syringe needle for auxiliary electrode. Adapted from Reference (40) with permission.

Table 2. Potentiometric mediated-titration of biological molecules with optically transparent thin-layer electrochemical cell...

Application of a potential step to a simple electrode reaction system such as Ox + ne = Red gives rise to the time-dependent absorbance of the electrode reaction products. The optically transparent thin-layer electrochemical cell has been successfully used to monitor this absorbance transient from which the kinetic parameters of the electrode reaction can be determined. 

We have been able to develop OTTLE (Optically Transparent Thin-Layer Electrochemical) cells with pathlengths as low as a few... 

Bill Heineman s group developed an elegant indirect titration method in the 1970s [15], Indirect coulometric titrations and optically transparent thin-layer electrochemical cells were combined to provide a simple and quick means of making formal potential measurements on electron transfer proteins. Moreover, the amount of sample required for this measurement was quite small. This is now a routine method for measuring the formal potential of electron transfer proteins, which is used by a wide range of non-electrochemical scientists. Use of this method in our laboratory, greatly facilitated by help from the Heineman laboratory, led to our later efforts to develop direct electfochemical methods for protein and enzyme studies. 

Method Abs, chemical reduction, monitored by absorption spectroscopy CD, chemical reduction, monitored by CD spectroscopy CD/OTTLE, electrochemical reduction using an optically transparent thin layer (OTTLE) cell, monitored by CD spectroscopy CV, cyclic voltammetry EPR, chemical reduction, monitored by EPR. 

Figure 2.105 Optically transparent thin layer electrochemical (OTTLE) cell. A = PTFE cell body, B = 13 x 2 mm window, (C and E) = PTFE spacers, D = gold minigrid electrode, F = 25 mm window, G = pressure plate, H = gold working electrode contact, 1 = reference electrode compartment, J = silver wire, K = auxiliary electrode and L = solution presaturator. From Ranjith...

The optically transparent thin-layer electrochemical (or OTTLE) cell has caught on to the greatest extent for UV-vis spectroelectrochemistry (Figure l).1-3 The OTTLE also offers a way to measure both the redox potential and the n-value without requiring knowledge of the electron... 

Figure 6.6 UV-Vis spectroscopic changes during electrochemical oxidation of (16-TMC)Ru(C=C-C6H4C1-4)2 in an optically transparent thin-layer electrolysis cell (0.1 M Bu4PF6/ CH2CI2 solution). Reproduced with permission from ref 57.

The electronic absorption data for the polyaammineruthenium dinuclear complexes were obtained by spectroelectrochemical studies, using an optically transparent, thin-layer electrochemical (OTTLE) cell. It is important that the effect of electrochemical titration on the... 

Figure 1 shows the structure of an optically transparent thin-layer electrochemical (OTTLE) cell [8]. 

The species C60 (n=0,1,2,3) have been electrogenerated in 0.5M Bu 4NBF4 in CH2CI2 solution at -60°C The UV and near-IR Spectra were recorded (in the range 5000cm 1 to 50000cm ) in an Optically Transparent Thin Layer Electrochemical (OTTLE) cell. 

Haiti F, Luyten H, Nieuwcmhuis HA, Schoemaker GC (1994) A versatile ciyostated optically transparent thin-layer electrochemical (OTTLE) cell for variable-temperature UV-vis/IR spectroelectrochemical studies. Appl Spectr48 1522... 

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]. 

Figure 18.16 Vacuum electrochemical cells (A) vacuum spectroelectrochemical cell that contains an optically transparent thin-layer electrode (OTTLE) and (B) electrochemical cell assembly. [From Ref. 45, with permission.]...

To resolve the difficulties described above, spectroelectrochemistry is used for monitoring redox processes in proteins. The method combines optical and electrochemical techniques, allowing the electrochemical signals (current, charge, etc.) and spectroscopic responses (UV-VIS, IR) to be obtained simultaneously. As a result, more information about the oxidation or reduction mechanisms of redox proteins can be acquired than with traditional electrochemical methods. Among the various spectroelec-trochemical techniques, in situ UV-VIS absorption spectroelectrochemistry in an optically transparent thin-layer cell has become one of the most useful methods for studying the direct electrochemistry of redox proteins. 

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