Thin Layer Electrochemical Cell Studies

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. 

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... 

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... 

This study on the immobilization of glucose oxidase and the characterization of its activity has demonstrated that a bioactive interface material may be prepared from derivatized plasma polymerized films. UV/Visible spectrophotometric analysis indicated that washed GOx-PPNVP/PEUU (2.4 cm2) had activity approximately equivalent to that of 13.4 nM GOx in 50 mM sodium acetate with a specific activity of 32.0 U/mg at pH 5.1 and room temperature. A sandwich-type thin-layer electrochemical cell was also used to qualitatively demonstrate the activity of 13.4 nM glucose oxidase under the same conditions. A quantitatively low specific activity value of 4.34 U/mg was obtained for the same enzyme solution by monitoring the hydrogen peroxide oxidation current using cyclic voltammetry. Incorporation of GOx-PPNVP/PEUU into the thin-layer allowed for the detection of immobilized enzyme activity in 0.2 M sodium phosphate (pH 5.2) at room temperature. 

Fig. 10.8 Thin-layer electrochemical cell used in SNIFTIR studies and reflection optics (a) Teflon cap (b) N2 inlet (c) glass tube (d) Teflon cell body (e) port for reference electrode (f) ceramic tube (g) Pt wire counter electrode (h) single crystal working electrode (i) hemispherical ZnSe window (k) focal plane for reflection optics (m) instrument focal plane and (n) folding mirrors (From reference 16, with permission.)...

Figure 4.6 Online coupling of an electrochemical flow cell with nanospray desorption electrospray ionization MS. (a) Scheme showing the configuration of the EC/nanospray desorption electrospray ionization MS with an electrochemical flow cell. Nanospray desorption electrospray ionization MS spectra acquired when the dopamine solution flowed through the thin-layer electrochemical cell with an applied potential of (b) 0.0 and (c) 1.5 V. (d) EIC of m/z 152 acquired when the dopamine solution flowed through the thin-layer electrochemical cell [ 175]. Reprinted with permission from Liu, R, Lanekoff, I.T., Laskin, ]., Dewald, H.D., Chen, H. (2012) Study of Electrochemical Reactions Using Nanospray Desorption Electrospray Ionization Mass Spectrometry. Anal. Chem. 84 5737-5743. Copyright (2012) American Chemical Society...

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... 

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. 

From the chemists point of view, PANI can be treated as a macromolecular polymer, lb elucidate its chemical structure, numerous spectroscopies have been employed. Vibrational spectroscopies have turned out to be most helpful. Infrared spectroscopy was initially employed ex situ (i.e., with dried samples outside the electrochemical cell) only later were adequate experimental designs developed for in situ studies with suitable thin layer electrochemical cells containing polymer-coated metal electrodes for external reflectance measurements. In many cases, IR spectroscopy is just used as a routine tool only those reports based on more intense applications are considered here [316-340]. A typical set of IR spectra of PANI exposed to an aqueous acidic electrolyte solution recorded in situ in the external reflection mode is shown in Figure 25. Interpretation of the spectra and assignment of the observed bands has been done by starting from two completely different points. In the classical approach, the polymer is treated as a collection of monomer units that show molecular connections. 

In addition to the more or less classical electroanalytical methods discussed above, the application of thin-layer electrochemical cells, spectroscopic characterization coupled with electrochemical generation, and the use of small digital computers coupled to electrochemical instru-mentation - for molten salt studies have been reported. 

Initially, a thin layer flow cell (Fig. 19) was used in this group to study the EC ALE formation of compounds [158] and in studies of electrochemical digital etching [312,313], Wei and Rajeshwar [130] used a flow cell system to deposit compound semiconductors as well, however, the major intent of that study was to form superlattices by modulating the deposition of CdSe and ZnSe. Their study appears to be the first example of the use of a flow electrodeposition system to form a compound semiconductor superlattice. 

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. 

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. 

The electrochemical cell design employed in thin-layer reflection-absorption studies is shown in Fig. 20. 

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... 

Study of the ECL based on Ru(bpy)3 revealed that luminescence intensity of monohydric alcohols decreased as alkyl chain length of the molecules increased while increase in the number of hydroxyl groups in a molecule leads to enhancement in limiinescence intensity for polyhydric alcohols [120]. Moreover, electrochemical redox potentials, PL, and relative ECL-FIA studies were described for polyamine dendrimers functionalized with electrochemiluminescent polypyridyl Ru(II) complexes, synthesized through the complexation of dendritic polypyridyl hgands to Ru(II) complexes [121]. The adaptability of the newly fabricated thin-layer electrochemical flow cell for amperometric and ECL measurements combined with FI method is demonstrated. This detection is followed by spectrophotometric detection for determination of bromide using the fabricated ceU [122]. 

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