Pyrolitic graphite electrodes

Figure 34 Cyclic voltammograms recorded at a pyrolitic graphite electrode in an aqueous solution (pH 7) containing (a) [(r -CsHs)Fe(rf-C5H4COOH)] (0.5 mM) and D-glucose (50 mM) (b) after the addition of glucose oxidase (10.9 nM). Scan rate 0.001 Vs 1...

Figure 7 Cyclic voltammograms of cytochrome c recorded at different types of pyrolitic graphite electrodes. Also shown are the relative ESCA spectral patterns which show the 0/C ratio in the different treated electrode material (a scale enlargement (x3) is shown for the Ojs peak)...

Figure 8 Cyclic voltammograms of cytochrome c recorded at an edge-oriented pyrolitic graphite electrode. In the absence (a) and in the presence (b) of [Cr(NH3)6]3 +...

Figure 15 Cyclic voltammogram recorded in a aqueous solution (pH= 7) of a cytochrome P450cam-DMPC thin film at a basal plane pyrolitic graphite electrode. Scan rate 0.1 V s l...

Figure 22 Cyclic voltammograms recorded in aqueous solutions of Rieske fragments from (a) bci complex glassy carbon working electrode pH 7.2 (b) (recombinant) biphenyldioxygenase (basal) pyrolitic graphite working electrode (in the presence of the positively charged additive neomycin) pH 7.0. Scan rate 0.01 V s ...

Since rusticyanin is positively charged (p/=9.1), its electrochemical response should be tested at negatively charged electrodes (namely, edge-plane pyrolitic graphite or glassy carbon electrodes). As a matter of fact, no positive response is obtained at a carbon paste electrode, but in the presence of a promoter such as 4,4/-bipyridyl a sufficiently resolved cyclic voltammetric response is obtained, Figure 37.67... 

Cyclic voltammogram recorded at a pyrolitic graphite electrode in an aqueous solution (pH 6.0) of Zucchini mavicyanin. Scan rate 0.02 V s J... 

Concerning the substrate, practically any material can be used to form a modified electrode, although the most used are gold, silver, platinum, mercury, and carbon (in its different variants, like glassy carbon, Highly Oriented Pyrolitic Graphite (HOPG), or Boron-Doped Diamond (BDD) electrodes [39]). 

Gold nanoparticles have been used to immobilize micro-peroxidase 11,46 tyrosinase,47 and hemoglobin48 to construct amperometric sensors, while silver nanoparticles have been used to enhance electron transfer of cytochrome c and myoglobin onto pyrolitic graphite electrodes.49 The use of semiconductor and oxide nanoparticles has also been reported, such as horseradish peroxidase (HRP) on TiC>2 nanoparticles,50 as well as Fe304 and MnC>4 nanoparticles to immobilize and facilitate direct electron transfer.51... 

Figure 4.39 Schematic representations of the various types of electrode surfaces for which protein voltammetry is commonly observed (a) a metal electrode modified with an XY SAM (b) a metal oxide electrode (c) an electrode modified with a surfactant layer in which protein molecules are embedded (d) a pyrolitic graphite edge electrode, often used in conjunction with mobile co-adsorbates such as aminocyclitols. Reprinted from Uectrochim. Acta, 45, F.A. Armstrong and G.S. Wilson, Recent developments in faradaic bioelectrochemistry, 2623-2645, Copyright (2000), with permission from Elsevier Science...

Detection of trichloroacetic acid via dechlorination to its di- and mono-chloroderivatives was also studied on a pyrolitic graphite electrode modified by Hb immobilized in poly-3-hydrobutyrate membrane (Ma et al. 2005). 

Compton et al. [40] proposed the immobilization of MWCNTs on basal plane pyrolitic graphite electrodes by abrasively attaching CNTs on the electrode siuface by gently rubbing a polished electrode on a filter paper containing 2 mg MWCNTs for 1 min. 

Luo et al. [43] proposed an electrode prepared by intercalation of CNTs in a pyrolitic graphite electrode previously polished with emery paper and alumina slurries and sonicated with water. It was performed by grounding the dry graphite electrode on a weighing paper containing a suitable amount of CNTs powder to intercalate them on the graphite smface by mechanical force and adsorption. 

Collman, and co-workers (346-352) also demonstrated that pyrolitic graphite electrodes modified with cofacial bis(porphyrinato cobalt) complex (CoFTF4) can promote the four-electron reduction of O2 to H2O. According to the proposed model, the dioxygen molecule is activated by the simultaneous coordination to two cobalt porphyrin sites, but electronic factors and/or the lack of electrons can also limit the four-electron process. 

FIGURE 7.15 CVs for4-chloro-2-nitrophenyl-derivatized carbon powder immobilized on basal plane pyrolitic graphite electrode in contact with 0.10 M HCl aqueous solution. The potential scan rate, 50 mV/sec. 

Moore, R.R., Banks, C.E., and Compton, R.G. (2004) Basal plane pyrolitic graphite modified electrodes comparison of carbon nanotubes and graphite powder as electrocatalysts. Arud. Chem., 76 (10), 2677 — 2682. 

As an example aiming at giving an idea of what can be made, in one of the first reports on electrocatalysis at a chemically modified electrode, a pyrolitic graphite electrode was treated by radio frequency plasma in oxygen, with subsequent attachment of benzidine to this treated graphite. The species on the surface catalizes ascorbic acid oxidation, which was, at that time, a new entry , though very popular in the rest of the story. .. [14]. 

For electrochemical and surface analytical investigations, the VOx-NTs were attached to pyrolitic graphite electrodes with the help of chitosan acting as binder. 

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