Electrochemical thin-layer

Gregory WB, Norton ML, Stickney JL (1990) Thin-layer electrochemical studies of the underpotential deposition of cadmium and tellurium on polycrystalline Au, Pt and Cu electrodes. J Electroanal Chem 293 85-101... 

Colletti LP, Teklay D, Stickney JL (1994) Thin-layer electrochemical studies of the oxidative underpotential deposition of sulfur and its application to the electrochemical atomic layer epitaxy deposition of CdS. J Electroanal Chem 369 145-152... 

Colleti LP, Thomas S, WUmer EM, Stickney JL (1997) Thin layer electrochemical studies of ZnS, ZnSe, and ZnTe formation by Electrochemical Atomic Layer Epitaxy (ECALE). Mater Res Soc Symp Proc 451 235. 

Hagans P, Homa A, Yeager E. 1979. In situ LEED-Auger-thin layer electrochemical studies of the underpotential deposition of Pb on Au single-crystals. J Electrochem Soc 126 (3) C147. 

Weber, S. G., The dependence of current on flow rate in thin-layer electrochemical detectors used in liquid chromatography. A clarification, /. Electroanal. Chem., 145, 1, 1983. 

The major applications of the OTTLE cell are (i) to obtain spectra of electrogenerated species and thence to obtain the extinction coefficients of its major absorption bands, and (ii) to determine the standard redox potential of a reversible couple. The latter experiment relies on the thin-layer electrochemical characteristics of the cell. Thus, for the couple ... 

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 starting potentials for most atomic layers, in this group, were obtained by studies of the voltammetry for an element on a Au electrode [130, 144-146], usually using a thin-layer electrochemical cell (TLEC) (Figure 13) [147, 148]. UPD potentials on Au are not expected to be optimal for growth of a compound however, they are generally a good start. 

Fig. 13. Schematic diagram of a thin layer electrochemical cell (TLEC).

FIG. 6. Diagram of thin-layer electrochemical cell (TLEC) (A) TLEC in conjunction with electrochemical H-cell (B) enlarged diagram showing pinhole region. (Erom Ref. 161.)... 

Square-wave voltammetiy apphed to experiments with a thin-layer electrochemical cell is a valuable analytical tool for determination of small amounts of analytes [46,154-157], e.g., the determination of drugs and species with biological activity [158]. Over the past decades, SWV has been frequently applied to study physiologically active compounds embedded in a thin-film that is imposed on an electrode snrface [78,159]. Moreover, a graphite electrode modified with a thin-film... 

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).

An operational definition of thin-layer electrochemistry is that area of electrochemical endeavor in which special advantage is taken of restricting the diffii-sional field of electroactive species and products. Typically, the solution under study is confined to a well-defined layer, less than 0.2 mm thick, trapped between an electrode and an inert barrier, between two electrodes, or between two inert barriers with an electrode between. Diffusion under this restricted condition has been described in Chapter 2 (Sec. II.C). Solution trapped in a porous-bed electrode will have qualitatively similar electrochemical properties however, geometric complexities make this configuration less useful for analytical purposes. The variety of electrical excitation signals applicable to thin-layer electrochemical work is large. Three reviews of the subject have appeared [28-30]. 

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.]...

Figure 11.9 Basic configuration for the specular reflectance thin-layer electrochemical cell. [From Ref. 4, with permission. Copyright 1970 American Chemical Society.]...

A. Yildiz, P. T. Kissinger, and C. N. Reilley, Anal. Chem. 40 1018 (1968). (A host of intriguing thin-layer cell applications are suggested, including the possibility of thin-layer electrochemical detectors for liquid chromatography, realized several years later by Kissinger and Adams.)... 

Figure 27.4 Five geometries for thin-layer electrochemical cells. Relative placement of the working (W), reference (R), and auxiliary (A) electrodes is shown.

Figure 27.7 Radial-flow thin-layer electrochemical cell for microbore chromatography.

HPLC-based electrochemical detection (HPLC-ECD) is very sensitive for those compounds that can be oxidized or reduced at low voltage potentials. Spectrophotometric-based HPLC techniques (UV absorption, fluorescence) measure a physical property of the molecule. Electrochemical detection, however, measures a compound by actually changing it chemically. The electrochemical detector (ECD) is becoming increasingly important for the determination of very small amounts of phenolics, for it provides enhanced sensitivity and selectivity. It has been applied in the detection of phenolic compounds in beer (28-30), wine (31), beverages (32), and olive oils (33). This procedure involves the separation of sample constituents by liquid chromatography prior to their oxidation at a glassy carbon electrode in a thin-layer electrochemical cell. 

The electronic tongue system based on flow injection analysis (FIA) with two amperometric detectors was set up. The FLA apparatus consisted of a Jasco (Tokyo, Japan) model 880 PU pump and two EG G Princeton Applied Research (Princeton, NJ, USA) Model 400 thin-layer electrochemical detector connected in series. Each detector was equipped with a working electrode (a dual glassy carbon electrode and a gold... 

Deng, H., and Van Berkel, G. J. (1999). A thin-layer electrochemical flow cell coupled online with electrospray-mass spectrometry for the study of biological redox reactions. 

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... 

Plasma polymerized N-vinyl-2-pyrrolidone films were deposited onto a poly(etherurethaneurea). Active sites for the immobilization were obtained via reduction with sodium borohydride followed by activation with l-cyano-4-dimethyl-aminopyridinium tetrafluoroborate. A colorometric activity determination indicated that 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. Using cyclic voltammetry of gold in thin-layer electrochemical cells, the specific activity of 13.4 nM glucose oxidase in 0.2 M aqueous sodium phosphate, pH 5.2, was calculated to be 4.34 U/mg at room temperature. Under the same experimental conditions, qualitative detection of the activity of a modified film was demonstrated by placing it inside the thin-layer cell. 

Thin-layer Studies. The thin-layer electrochemical system was developed to address the lack of sensitivity of a preliminary bulk amperometric activity assay (77). The first set of thin-layer studies was taken to characterize the thin-layer cells in soluble enzyme solutions and to determine if there were any interferences to the detection of hydrogen peroxide. Preliminary thin-layer studies (23) indicated that the oxidation of hydrogen peroxide could be detected at approximately 1080 mV with only minimal interference from the oxidation of glucose by gold. The addition of chloride ion to the solution further suppressed the glucose electrooxidation interference. 

Figure 1. Thin-layer electrochemical detector ( (A) auxiliary electrode (R) reference electrode (W) working electrode)...

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