Basal plane pyrolytic graphite

The presence of redox catalysts in the electrode coatings is not essential in the c s cited alx)ve because the entrapped redox species are of sufficient quantity to provide redox conductivity. However, the presence of an additional redox catalyst may be useful to support redox conductivity or when specific chemical redox catalysis is used. An excellent example of the latter is an analytical electrode for the low level detection of alkylating agents using a vitamin 8,2 epoxy polymer on basal plane pyrolytic graphite The preconcentration step involves irreversible oxidative addition of R-X to the Co complex (see Scheme 8, Sect. 4.4). The detection by reductive voltammetry, in a two electron step, releases R that can be protonated in the medium. Simultaneously the original Co complex is restored and the electrode can be re-used. Reproducible relations between preconcentration times as well as R-X concentrations in the test solutions and voltammetric peak currents were established. The detection limit for methyl iodide is in the submicromolar range. 

A. Salimi, R.G. Compton, and R. Hallaj, Glucose biosensor prepared by glucose oxidase encapsulated sol-gel and carbon-nanotube-modified basal plane pyrolytic graphite electrode. Anal. Biochem. 333, 49— 56 (2004). 

R.R. Moore, C.E. Banks, and R.G. Compton, Basal plane pyrolytic graphite modified electrodes comparison of carbon nanotubes and graphite powder as electrocatalysts. Anal. Chem. 76, 2677—2682... 

Fig. 2.51 Forward and reverse square-wave voltammograms of myoglobin-didodecyldimethyl-ammonium bromide films on a basal plane pyrolytic graphite eleetrodes at 200 Hz frequency, 10 mV step height, and different pulse heights. Points are experimental data, and lines are best fits by nonlinear regression onto the Mareus model. Baekground eurrents are ineluded in experimental and eomputed data. T = 37.0 0.2 °C, and the supporting eleetrolyte is 20 mmol/L pH 6.0 phthalate buffer +180 mmol/L NaCl (reprinted from [78] with permission)...

This method involves electrochemical deposition of the MPc onto CNT-modified electrode surface by repetitive cycling in a concentrated MPc solution (1 mM) within a specific potential window. The first cyclic voltammetric scan is usually similar to subsequent scans, indicating the formation of monomeric species only. Ozoemena et al [11] found that on certain occasions, as reported recently [11] during the electro-deposition of CoTAPc onto a basal plane pyrolytic graphite electrode (BPPGE) pre-modified with SWCNT, both cathodic and anodic waves may decrease continually and then stabilizes at a certain scan (a process known as electrochemical adsorption or simply called electrosorption ). 

Clay/ionic liquid modified electrodes Sun investigated the use of Hb/clay/IL composite MEs for the electrocatalytic detection of HjOj, TCA, and nitrite [43]. The IL [C4CiIm][PFg] (2 mL) was stirred with bentonite clay (1 mg) for 1 h after which 1 mg of Hb was dispersed into the mixture. A volume of this dispersion was then cast onto a freshly polished basal plane pyrolytic graphite (BPPG) electrode. UV-Vis studies revealed the position of the Hb Soret band to be 410 and 412 nm for dry and buffer-immersed films, respectively. This is consistent with a near-native environment surrounding the heme within Hb in the Hb/clay/... 

Bond AM, Marken F, Hill E, Compton RG, Hiigel H (1997) The electrochemical reduction of indigo dissolved in organic solvents and as a solid mechanically attached to a basal plane pyrolytic graphite electrode immersed in aqueous electrolyte solution. J Chem Soc Perkin Trans 2 1735-1742. 

Kano K, Uno B (1993) Surface-redox reaction mechanism of quinones adsorbed on basal-plane pyrolytic graphite electrodes. Anal Chem 58 2009-2012. 

Finally in this section it is worth noting that the oxidative coupling of phenols may be extended to form interesting polymers. Thus electrooxidative polymerization of phenol using basal-plane pyrolytic graphite electrodes gives thin black polymer films which are electrically conducting. ... 

In-situ STM of laccase has so far been attempted using only basal-plane pyrolytic graphite surfaces [54]. No adsotption could be detected. This is perhaps not surprising as laccase voltammetry requires edge-plane graphite and/or pre-adsorption of promoters. Low-resolution ex-situ micron-scale laccase structures coidd be recorded during evaporation of laccase solution where individual molecular-size structures, possibly dislodged by mechanical tip contact, could also be observed. 

Adsorbed layers of cytochrome c3 have also been used to facilitate electron transfer of molecules that otherwise would not yield high electron-transfer rates. Facilitated electron transfer has been observed for flavodoxin and ferredoxin on cytochrome c3 modified basal plane pyrolytic graphite (26). 

The first one is an adsorption monolayer of MB on a basal plane pyrolytic graphite (BPG) electrode surface [9, 24, 25]. Eig. 2.7 a shows the experimental set-up and Eig. 2.7b shows the plot of the change ARic(E) at constant electrode potentials. The experimental ARi E) can actually fit to a Nernst equation ... 

Fig. 2.7 (a) Experimental set-up for a nearnormal incidence UV-visible reflectance measurement at constant potential for a basal plane pyrolytic graphite (BPG) electrode, (b) Plot of the change of dc reflectance as a function of electrode potential at A=737 nm at a BPG electrode... 

Preparation of CoPc in PVP A mixed solution of DMF CoPc (Kanto Chemical Co.Inc. 5 to 50 jimol dm" ) and PVP (1 wt.%, prepared by radical poljnnerisation of 4-vinylpyridine) was prepared, and this solution (2 pL) was cast on a basal plane pyrolytic graphite electrode (BPG) (effective area 0.17 cm ) followed by solvent evaporation under ambient conditions. 

Fig. II.1.26 (a) Cyclic voltammogram [123] obtained in aqueous (0.1 M NaC104) media at 20°C for solid rran -[Cr(CO)2(dpe)2l mechanically attached to a polished basal plane pyrolytic graphite electrode (scan rate = 50 mV s ). (b) Schematic representation of redox processes at the interface between solid, electrode surface, and liquid electrolyte system...

Electrodes were prepared by attaching the cylindrical disk of basal plane pyrolytic graphite (BPG) (Union Carbide Co.) on the edge of stainless rod by conductive polymer paste, then they were sealed with heat-shrinkable olefin tube. All electrodes employed in this study had geometric area of 0.17 cm. Fresh electrode surfaces were produced by cleaving the disk of BPG with a scalpel. The polymers or polymer complexes were directly coated on the electrode by casting method as described previously. ... 

Recently, Marken and coworkers [135] reported a novel method for the electrogeneration of ionic liquids in which microdroplets of N, N, N, N -. e. xah.exy -para-phenylene diamine (THPD) are deposited upon the surface of a basal plane pyrolytic graphite (or gold) electrode and are immersed into an aqueous electrolyte solution. The ionic liquid is formed as a consequence of the requirement to maintain electroneutrality upon oxidizing THPD,... 

SWV—square wave voltammetry CV—cyclic voltammetry PG—ordinary basal plane pyrolytic graphite EPG—edge plane pyrolytic graphite ITO— indium tin ojside. 

Fig. 9.11 Basal-plane pyrolytic graphite electrode in vitamin Bi2r at a scan rate of 0.5 V for (a) unmodified BPPG in 1.2 mM vitamin Bur solution, (b) modified BPPG with DBCH in buffer solution, and (c) modified BPPG in vitamin Bi2r solution. Reproduced from P. Tomcik et al, Anal. Chem. 76 (2004) 161, with permission from the American Chemical...

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