Carbon reticulated vitreous

A similar, but highly porous, vitreous carbon material—reticulated vitreous carbon (RVC)—has found widespread application for flow analysis and spectro-electrochemistry (25). As shown in Figure 4-10, RVC is an open-pore ( spongelike ) material such a network combines the electrochemical properties of glassy carbon with many structural and hydrodynamic advantages. These include a very high surface area ( 66 cm2 cm-3 for the 100-ppi grade), 90-97% void volume, and a low resistance to fluid flow. 

FIGURE 4-10 The open-pore structure of reticulated vitreous carbon. 

Redox switching, 126 Reference electrodes, 100, 105, 142 Reflectance spectroscopy, 44 Resistance, 22, 105 Resolution 50, 71 Reverse pulse polarography, 68 Reversible systems, 4, 31 Reticulated vitreous carbon, 114, 115 Riboflavin, 37... 

If the electrochemical sensor does not require a permselective membrane, immobilization of the enzyme onto the surface of the electrode is possible. Glassy carbon graphite reticulated vitreous carbon and carbon paste electrodes... 

Kirkpatrick, M.J., Finney, W.C. and Locke, B.R. (2003) Chlorinated organic compound removal by gas phase pulsed streamer corona electrical discharge with reticulated vitreous carbon electrodes, Plasmas and Polymers 8, 165-77. 

These authors have also developed a cell98 (Fig. 26) that employs reticulated vitreous carbon as a working electrode and they find that such a design allows for much faster electrolysis. Using such a cell, they have studied the [Ru(NH3)6]3+/2+ couple... 

Several approaches have been undertaken to construct redox active polymermodified electrodes containing such rhodium complexes as mediators. Beley [70] and Cosnier [71] used the electropolymerization of pyrrole-linked rhodium complexes for their fixation at the electrode surface. An effective system for the formation of 1,4-NADH from NAD+ applied a poly-Rh(terpy-py)2 + (terpy = terpyridine py = pyrrole) modified reticulated vitreous carbon electrode [70]. In the presence of liver alcohol dehydrogenase as production enzyme, cyclohexanone was transformed to cyclohexanol with a turnover number of 113 in 31 h. However, the current efficiency was rather small. The films which are obtained by electropolymerization of the pyrrole-linked rhodium complexes do not swell. Therefore, the reaction between the substrate, for example NAD+, and the reduced redox catalyst mostly takes place at the film/solution interface. To obtain a water-swellable film, which allows the easy penetration of the substrate into the film and thus renders the reaction layer larger, we used a different approach. Water-soluble copolymers of substituted vinylbipyridine rhodium complexes with N-vinylpyrrolidone, like 11 and 12, were synthesized chemically and then fixed to the surface of a graphite electrode by /-irradiation. The polymer films obtained swell very well in aqueous... 

The oxidation of enol ethers at a reticulated vitreous carbon anode [2, 3] (Scheme 1) in a mixture of methanol/THF containing tetraethylammonium tosylate as the electrolyte and 2,6-lutidine as the base leads to substituted tetrahydrofu-ran and tetrahydropyran rings in good yields (51-96%). The major product obtained had a trans-stereochemistry. The cyclization failed to make seven-membered ring products. In order to determine the... 

The first coupling reaction of this type studied utilized a 3-methoxyphenyl ring as the aryl coupling partner (Scheme 36) [47a, c]. The reaction employed constant current electrolysis conditions and a reticulated vitreous carbon anode (RVC). A good yield of cyclized material was obtained. However, the reaction was plagued by the formation of secondary products derived from over-oxidation (35 and 36) of the initially formed cyclization products (33 and 34). The amount of over-oxidized material could be greatly reduced with the use of controlled potential electrolysis conditions. 

Figure 3. Electrolyses of 50 mM Na2S04 adjusted to pH 2 continuously saturated with O2 at a reticulated vitreous carbon cathode in a flow-cell. Plots of H2O2 formed versus electrolysis time for...

Figure 10. COD evolution as a function of electrolysis time for electrolysis of solutions containing 50 mMNa2S04 + 1 mMFe + dye (a) 0.082 mMDR23, (b) 0.25 mM A07, (c) 0.33 mM Am, (d) 0.1 mM AG25, (e) 0.1 mM Am, (f) 0.17 mM BB9. Electrolyses were carried out in a membrane cell with a reticulated vitreous carbon cathode (5 cm x 5 cm x 1 cm).

The feasibility of benzenic ring amines, benzenic ring structures and aliphatic acids oxidation by means of Fenton chemistiy was tested in synthetic, acidic wastewaters by Fenton s reagent electrogenerated at a reticulated vitreous carbon cathode using the flow-cell. The organic molecules considered were phenol (Ph), cresol (Cr), aniline (An) hydroquinone (HQ), catechol (Cat), parabenzoquinone (pBQ) and oxalic acid (OxAc). Their initial... 

Radical intermediates are also trapped by intramolecular reaction with an alkene or alkyne bond. At a mercury cathode this process competes with formation of the dialkylmercury [51], At a reticulated vitreous carbon cathode, this intramolecular cyclization of radicals generated by reduction of iodo compounds is an important process. Reduction of l-iododec-5-yne 5 at vitreous carbon gives the cyclopentane... 

Several reticulated vitreous carbon (RVC)-plant tissue composite electrodes have also been reported where the open-cell structure of RVC serves as a template for the biocomponent used. One such sensor was constructed by press-fitting 100 pore/in RVC (2-mm thick x 3 or 6 mm OD) cylinders into a 6-mm diameter cavity of a thin-layer cell. The inner side of the disc was pressed into an edge of a copper wire, which provided electrical contact. 

Radical cations of 2-alkylidene-l,3-dithianes can be generated electrochemically by anodic oxidation using a reticulated vitreous carbon (RVC) anode <2002TL7159>. These intermediates readily react with nucleophiles at C-1. Upon removal of the second electron, the sulfur-stabilized cations were trapped by nucleophilic solvents, such as MeOH, to furnish the final cycloaddition products. Hydroxy groups <20010L1729> and secondary amides <2005OL3553> were employed as O-nucleophiles and enol ethers as C-nucleophiles (Scheme 50) <2002JA10101>. 

Czerwihski and coworkers [345] reviewed the electrochemical applications of reticulated vitreous carbon (RVC). Special attention was paid to the use of RVC as an electrode support in zinc-manganese and zinc-halogen batteries. 

Other Substrates Deposition of cadmium was also studied on Bi, Sn and Pb [303], Ni [304], reticulated vitreous carbon [305], Ti [306], and indium tin oxide [307]. UPD of Cd on tellurium results in CdTe formation [270, 308]. Electrodes coated with conducting polymers were also used to deposit cadmium electrochemi-cally. In the case of polyaniline, the metal reduction potential corresponds to the neutral (nonconducting) state of the polymer, therefore cadmium was found to deposit on the substrate-glassy carbon electrode surface, in the open pores of the polymer film [309, 310]. 

Properties of thin layers of lead electrodeposited on vitreous carbon have been found identical with that of metallic lead [304]. Therefore Pb and Pb02 coated reticulated vitreous carbon (RVC) electrodes [185] can be applied as electrodes in lead-acid batteries, as reviewed in [305]. The deposition of lead on carbon is through the diffusion-controlled process with instantaneous or progressive nucleation, for high and low Pb + concentration, respectively, and three-dimensional growth mechanism. The number of nucleation sites increases with deposition overpotential, as shown for vitreous [306] and glassy carbon [307] electrodes. The concentration dependence of the nucleation... 

Film Electrodes and Related Hg Electrodes Mercury films were prepared on reticulated vitreous carbon flowthrough electrodes by Hg deposition from Hg + solutions in acetic buffer [31]. Such an electrode was designed for the purposes of trace metal analysis. Mercury film de-position/oxidation on reticulated vitreous carbon and glassy carbon electrodes were compared. 

Figure 9.10 Assembly of sandwich-type optically transparent electrochemical cell for extended x-ray absorbance fine structure (EXAFS) spectroelectrochemistry. Cell body is of MACOR working electrode is reticulated vitreous carbon (RVC). [From Ref. 64, with permission.]...

Pena et al. [57] Beer Alcohol oxidase, peroxidase/ physically entrapped in the electrode matrix Reticulated vitreous carbon (RVC)-epoxy resin electrode/OV vs. Ag/AgCl Ferrocene (physically entrapped in the electrode matrix)... 

N. Pena, R. Tarrega, A.J. Reviejo and J.M. Pingarron, Reticulated vitreous carbon-based composite bienzyme electrodes for the determination of alcohols in beer samples, Anal. Lett., 35(12) (2002) 1931-1944. 

Kent BL, Mutharasani R (1992), Cultivation of animal cells in a reticulated vitreous carbon foam, J. Biotechnol. 22 311-328. 

Electropolymerized films have been used to prevent interferences and fouling in biosensors constructed from reticulated vitreous carbon and platinum disk electrodes (14,15). A biosensor constructed using electropolymerized films can have significantly improved diffusional properties due to the thinness of the film. By engineering the components and properties of a biosensor on a microscopic scale, rather than using "bulk-technology" and physically assembling discrete macroscopic components, as is the conventional practice, an all-chemical method of construction can be achieved. All-chemical methods of construction would... 

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