Modifying glassy carbon (GC) electrodes to confer selectivity for the voltammetric detection of L-cysteine in the presence of DL-homocysteine and glutathione

In this communication we report a proof of concept study of the use of cyclic voltammetry with a polyeugenol-modified glassy carbon (GC) electrode to selectively detect L-cysteine in the presence of both DL-homocysteine and glutathione in perchloric acid. The formation of a polyeugenol-modified gold electrode is also reported for the first time. © 2008 Wiley-VCH Verlag GmbH and Co. KGaA

Behaviour of the anion radicals electrochemically generated in the reduction of nosyl amides

The behaviour of nitrobenzenesulfonamide anion radicals generated from the electrochemical reduction of aliphatic and aromatic amines protected by nitrobenzenesulfonyl (nosyl) groups in Ν,Ν’ dimethylformamide has been reported. The species have been characterized by voltammetry and optical and electron spin resonance spectroscopies. The visible spectra of the anion radicals were recorded and the hyperfine splitting constants were assigned to specific proton positions and nitrogen nuclei of the molecule. The stabilities of the anion radicals are affected by electronic properties of the protecting group and specific features of the amines, which show direct influence on the route of cathodic cleavage of the nitrobenzenesulfonamides

The Fabrication and Characterization of a Nickel Nanoparticle Modified Boron Doped Diamond Electrode for Electrocatalysis of Primary Alcohol Oxidation

We report the fabrication of a Ni nanoparticle modified BDD electrode and its application in the electrocatalysis of primary alcohol electrooxidation. Modification was achieved via electrodeposition from Ni(NO3)2 dissolved in sodium acetate solution (pH 5). Characterization of the Ni-modified BDD (Ni-BDD) was performed using ex situ atomic force microscopy (AFM) and high resolution scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). Large nanoparticles of nickel were observed on the BDD surface ranging 5 to 690 nm in height and 0.18 μm3 in volume, and an average number density of ca. 13 × 106 nanoparticles cm-2 was determined. The large range of sizes suggests progressive rather than instantaneous nucleation and growth. Electrocatalysis of ethanol and glycerol, was conducted in an alkaline medium using an unmodified BDD, Ni-BDD and a bulk Ni macro electrode. The Ni-BDD electrode gave the better electrocatalytic performance, with glycerol showing the greatest sensitivity. Linear calibration plots were obtained for the ethanol and glycerol additions over concentration ranges of 2.8 - 28.0 mM and 23 - 230 μM respectively. This gave an ethanol limit of detection of 1.7 mM and sensitivity of 0.31 mA/M, and the glycerol a limit of detection of 10.3 μM with a sensitivity of 35 mA/M. © 2009 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim

Electrochemical polymerisation studies of aza-15-crown-5 vinyl-2,2'-bipyridine ruthenium(II) complexes

The electrochemical polymerisation of the mono(ligand) and tris(ligand) ruthenium(II) complexes, [RuL1,2(bipy)2]2+ and [RuL1,23]2+ (bipy = 2,2′-bipyridine, L1 = 4-methyl-4′-(N-styryl-aza-15-crown-5)-2,2′-bipyridine, L2 = 4,4′-bis(N-styryl-aza-15-crown-5)-2,2′-bipyridine), has been investigated in acetonitrile. Preparation of electroactive polymer films was established on reductive electropolymerisation of the tris(ligand) ruthenium(II) complexes. Electropolymerisation of [RuL1(bipy)2]2+ did not take place, suggesting that the polymer formation mechanism involves radical-radical hydrodimerisation for pairs of vinyl groups rather than 'polyvinyl-type' chain propagation. Lack of electropolymerisation for [RuL2(bipy)2]2+, with two vinyl linkages on the same ligand, is explained by steric constraints preventing repeated linkages between aza-15-crown-5 vinyl-pyridine units. While polymer formation via the alternative route of oxidative coupling of the N-styryl-aza-15-crown-5 moieties might be anticipated, electro-oxidation for the [RuL2(bipy)2]2+ and [RuL1,23]2+ complexes led only to the formation of electroinactive orange films with concurrent electrode passivation

Components of all-solid-state ion-selective electrodes

An electrochemical sensor is a qualitative and quantitative device that converts a chemical signal to a measurable electrical signal (Yogeswaran and Shen-Ming 2008). Electrochemical sensors can be divided into three classes: potentiometric, amperometric, and conductometric (Stradiotto et al. 2003). A potentiometric sensor measures an electrical potential when no current is present, while an amperometric sensor produces current when a potential is applied between two electrodes. A conductometric sensor assesses conductivity by measuring the electrical resistance of a sample solution. Ion-selective electrodes (ISEs) are potentiometric ion sensors and a subgroup of electrochemical sensors; they are widely used in various fields of biomedical, environmental, and chemical analysis, and physiological sensing (Bobacka et al. 2003; Bakker et al. 2008; Hu et al. 2016). ISEs are classified into three groups, depending on the nature of the membrane material: glass, polymeric or liquid, and crystal or solid (Fig. 16.1) (Faridbod et al. 2007)