Glassy carbon-modified electrodes

Evidence of the electrical conductivity of DNA and of its important mechanisms has been discussed for a long time and has led to a theory of electron conduction in biopolymers [25, 82]. From this it appeared that the major carrier of conductivity is either electronic or ionic, depending on the temperature of the sample, the water content, and the fact that the conductivity of native samples is higher than that of denatured samples. Following electrochemical oxidation of dsDNA and ssDNA in electrolyte solutions over a wide range of pH, interesting electrochemical properties of a glassy carbon electrode with dsDNA or ssDNA adsorbed on the electrode surface were observed [68]. 

The ssDNA was prepared by treating a sample of calf thymus DNA of approximately 4 mg of dsDNA with 0.5 mL of 60% pure perchloric acid after dissolution, 0.5 mL of 9 M NaOH were immediately added to neutralize the solution followed by 9 mL of pH 4.5 acetate buffer. The DNA-modified glassy carbon electrode was prepared by covering a glassy carbon electrode with 3 mg of dsDNA dissolved in 80 jjlL of pH 4.5 acetate buffer and leaving the electrode to dry. The DNA layer was 0.5 mm thick and 

These interesting observations could be explained through the formation of triple helix DNA on the electrode surface. Side- and main-chain atoms may interact with a particular DNA base-pair of another chain or with more than one base-pair supporting each other in interwoven hydrogenbonding networks that stabilize the contacts between the bases, forming a triple helix on the DNA adsorbed to the electrode surface [9-11]. The triple helix DNA is formed by interaction of the ssDNA in the bulk 

This modified electrode was used to evaluate the electrochemical oxidation of guanosine and adenosine 3 -monophosphates. A similar conclusion 

If we consider Figs. 3.8 and 3.9, where the results for the oxidation of guanosine and adenosine 5 -monophosphates at a bare glassy carbon electrode and at a DNA-modified electrode are presented, several facts are worth mentioning when comparing voltammograms at both electrodes. 

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Trace mercury determination by differential pulse (dp) anodic stripping voltammetry on polythiophene-quinoline/glassy carbon modified electrode has been reported [77]. 

Casclla, LG., Cataldi, T.R.L, Salvi, A.M., and Desimoni, E. 1993. Electrocatalytic oxidation and liquid chromatographic detection of aliphatic alcohols at a nickel-based glassy carbon modified electrode. Analytical Chemistry 65, 3143-3150. 

Riqelme, M.A., M. Isaacs, M. Lucero, E. Trullund, M.J. Aguirre, and J. Canales (2003). Electrocatalytic reduction of carbon dioxide at polymeric cobalt tetra(3-aminophenyl) porphyrin glassy carbon-modified electrodes. J. Chilean Chem. Soc. 48(2), 89-92. 

Dreyse P, Isaacs M, Calfuman K, Caceres C, Aliaga A, Aguirre MJ, Villagra D (2011) Electrochemical reduction of nitrite at poly-[Ru(5-N02-phen)2Cl] tetrapyridylpoiphyrin glassy carbon modified electrode. Electrochim Acta 56(14) 5230-5237... 

Dreyse P, Quezada D, Honores J, Aguirre MJ, Mendoza L, Matsuhiro B, Villagra D, Isaacs M (2012) Determination of S(1V) oxoanions at Poly[Ru(5-N02-Phen)2Cl] tetrapyridylpoiphyrin glassy carbon modified electrode. Electroanal 24(8) 1709-1718... 

Calfuman K, Aguirre M, Villagra D, Yanez C, Arevalo C, Matsuhiro B, Mendoza L, Isaacs M (2010) Nafion/tetraruthenated porphyrin glassy carbon-modified electrode characterization and voltammetric smdies of sulfite oxidation in water-ethanol solutions. J Solid State Electrochem 14(6) 1065-1072... 

Fuenzalida F, Dreyse P, Villagra D, Matsuhiro B, Mendoza L, Aguirre MJ, Isaacs M (2009) Electrochemical reduction of SO2 on poly-Co-3-tettaaminophenylporphyrin glassy carbon modified electrode. J Coord Chem 62 130 140... 

U.A. Kirgoz, S. Timur, J. Wang, and A. Teleponcu, Xanthine oxidase modified glassy carbon paste electrode. Electrochem. Commun. 6, 913—916 (2004). 

Another recent topic in detection of OP compounds based on ChE-modified biosensors is to use carbon nanotubes (CNTs) as an electrode modifier. CNTs are known to exhibit excellent electrochemical properties originating from high catalytic activity of edge-plane-like graphite sites at CNT ends and a large effective surface area. Lin et al. (2004) have reported that stable CNT-modified glassy carbon (GC) electrodes can be prepared by coating the surface of GC electrode with a suspension of CNT and can be used for sensitive determination of thiocholine (Liu etal,... 

The greatest interest in Nafion (Nf), a perfluorinated polymer with sulfonate groups, derives from its consideration as a proton conducting membrane in fuel cells to many sensor applications [37], The use of Nf and other polyanions to control ion-transport during electrode reaction is a recurring theme [38], The electrodeposition of platinum nanoparticles at the Nafion (Nf) modified glassy carbon (GC) electrode (GC/Nf/Ptnano) by the two-step method... 

Glassy carbon felt electrodes modified by electrodeposited poly(pyrrole-viologen) films containing electroprecipitated microparticles of precious metals like Pt, Pd, Rh or Ru have been shown to be suitable for the electrocatalytical hydrogenation of several organic substrates including benzonitrile, in acidic aqueous solution. Pd exhibited the highest current efficiency and yields for benzylamine formation when compared with Pt and Rh. 

Varma S, Mitra GK. Bioelectrochemical studies on catalase modified glassy carbon paste electrodes. Electrochemistry Gommunications 2002 4 151-157. 

In order to accelerate electrooxidation of NADH, attempts are being made to develop chemically modified electrodes. Positive effects have been observed in the case of glassy carbon modified with 3,4-dihydroxybenzyl-... 

In a cyclic voltammogram recorded with a glassy carbon disk electrode modified by the crosslinked Co-PEI complex film, the uncatalyzed reduction of oxygen was observed at potentials lower than -0.3 V. As such, a significant increase in the current magnitude was noted for the electrode surface modified with the thin Co-PEI membrane under an air atmosphere due to the oxygen enrichment from the aqueous phase. 

Various chemically modified electrode configurations have been investigated to optimize the current response and lower the overpotential. A hypox-anthine biosensor has been reported based on a glassy carbon paste electrode modified with Au nanoparticles and XO. The enzyme modified electrode shows catalytic activity at +500 mV vs. Ag/AgCl, which is 250 mV less positive than in the absence of the Au nanoparticles. Pundir and coworkers have extensively studied an XO-based biosensor with several nanomaterials and xanthine concentrations were determined by the measurement of H2O2 produced at +600 mV vs. Ag/AgCl. The biosensor was used for quantification of xanthine in tea leaves, coffee powder and fish meat. 

Ohsaka and coworkers initially reported the outstanding catalytic enhancement of OER of MnO,c nanorod modified platinum, gold and glassy carbon (GC) electrodes and evaluated the loading level of MnO (in the manganite phase, y-MnOOH) and the pH of the electrolyte for OER. The nanorods showed a maximum activity in basic medium and the... 

This electron transfer was positively affected by the immobilization of glucose oxidase on glassy carbon modified by aminophenyl boronic acid [193] or adsorption on to metalized carbons [194]. Nevertheless, it was possible to achieve good electron transfer only by modification ( functionalization ) of the enzyme with redox compounds (ferrocene derivatives). The direct electrical communication between the modified enzyme and an electrode has been proved by cyclic voltammetry. Thus attention was paid to the construction of various types of modified glucose oxidase electrodes. For instance, Benneto et al. [195] describe an... 

A simple and quick method in FIA using a glassy carbon disk electrode modified with a molybdenum oxide film has been proposed for the quantification of iodate in commercial salt samples [48]. In this study, the film actuated as a catalytic agent in the reduction of iodate and a linear response was observed (from 1.0 x 10 to 1.0 x 10 mol r ). Other amperometric method coupled to FIA exploring the electrochemical reduction of iodate was also described [49]. Here, the authors used a more favorable working potential (+0.2 V vs. Ag/AgCl) in the presence of a solution of 1.0% w/v NaCl, 0.02% w/v KI, and 0.1 mol 1 HCl as carrier. 

Cubukcu, M., Timur, S., Anik, U., 2007. Examination of performance of glassy carbon paste electrode modified with gold nanoparticle and xanthine oxidase for xanthine and hypoxan-thine detection. Talanta 74,434-439. 

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