Cyclic voltammetry of dye-modified supported bilayer lipid membranes (s-BLMs)

The voltammetric behaviour of dye-modified supported bilayer lipid membranes is investigated. (C) 1997 Elsevier Science S.A.

Probe beam deflection combined with cyclic voltammetry studies of C-60-modified electrode film

C-60 films, prepared by solution casting, were studied by means of in situ probe beam deflection (PBD) combined with cyclic voltammetry (CV). PBD is a powerful technique for investigation of phenomena at the electrode/electrolyte interface in acetonitrile with quaternary ammonium and alkali metal salts as supporting electrolytes. In tetra-n-butylammonium (TBA(+)) salt solution, a stable CV can be obtained during the first two reduction/reoxidation waves. On reduction, injection of cations to maintain charge balance and dissolution of small amount of C-60(-) (TEA(+)) and/or C-60(2-) (TBA(+))(2) are detected. During the reoxidation process ejection of cations and injection of anions occur simultaneously, especially for the second reoxidation wave. In the case where TBABr is the supporting electrolyte, the accompanied behavior is more complicated than in TBABF(4), TBAClO(4), and TBAPF(6) solutions. A small pair of prewaves in CV are proposed due to oxidation/reduction of C-60 domains but not dissolution/redeposition of C-60 film. Extending the potential scan range to the third reduction wave, no apparent corresponding reoxidation wave is related to the third reduction wave, the electroactivity of the film disappears rapidly and dissolution of C-60 film is observed. In tetraethylammonium (TEA(+)) and NAClO(4) solutions, the electrochemistry of the C-60 films is unstable, and potential scans lead to dissolution of flaking of the film.

Study on ferrocene derivatives diffusion dynamics in polymer electrolyte by solid-state voltammetry

The diffusion rates of seven ferrocene derivatives have been estimated in polyelectrolyte PEG . LiClO4 by using non-steady-state chronoamperometry. The D-app of ferrocene derivatives increases with temperature, and the dependency of D-app on temperature obeys the Arrhenius equation. The D-app of ferrocene derivatives decreases with increasing size of electroactive species. The Delta D-app values of D-T>Tm and D-T T-m in the polyelectrolyte. On the other hand, the diffusion behaviour of ferrocene derivatives is qualitatively analyzed by using cyclic voltammetry. Copyright (C) 1996 Elsevier Science Ltd

VOLTAMMETRY OF CYTOCHROME-C ENTRAPPED IN HYDROGEL MEMBRANE ON GRAPHITE ELECTRODE

The voltammetric behavior of cytochrome c entrapped in hydrogel membranes at paraffin wax-impregnated spectroscopic graphite electrodes (WISGE) was studied in this paper. A pair of well-defined peaks appeared at +70 mV (vs. Ag/AgCl). Beside these two peaks, another pair of peaks emerged at around +225 mV. Further investigations suggested that at least three states of cytochrome c existed in the membranes due to the special structure of the hydrogel. The native conformation of cytochrome c molecules was stabilized by the hydrophilic environment that was formed by the hydroxyl structure of the membranes and facilitated the cytochrome c electron transfer reaction at +70 mV. The molecules directly adsorbed on the surface of the graphite electrode were responsible for the redox peaks at around +225 mV. Whether the adsorption peaks were detectable or not was related to the thickness of membranes and the pre-retaining time before the formation of membranes.

SOLID-STATE VOLTAMMETRY OF ELECTROACTIVE SOLUTES IN POLYMER SOLVENTS (PEO) AT ULTRAMICROELECTRODES

This paper describes the electrochemical oxidation and reduction of electroactive solutes which are dissolved in and diffusing through the polymer electrolyte solvent, poly(ethylene oxide) (PEO). The characteristics of electrochemical reactions in polymeric solutions are discussed, including how rigid solvent environments affect mass transport rates, and the transport phenomenon of electroactive species in PEO with bathing gases is explained by using the voltammetric theory of ultramicroelectrodes. The possibility that the microelectrode coated with PEO film can be used as a gas sensor has been discussed.

EFFECTS OF DOPANT AND SOLVENT ON THE PROPERTIES OF POLYPYRROLE - INVESTIGATIONS WITH CYCLIC VOLTAMMETRY AND ELECTROCHEMICALLY INSITU CONDUCTIVITY

A new method for electrochemically in situ conductivity measurements based on a reusable glassy carbon disc carbon fibre array double electrode is described. Using this technique and cyclic voltammetry, we have investigated the effects of the doping anion and solvent on the electrochemical properties of polypyrrole film. The electroactivity and potential dependent conductivity of polypyrrole film are strongly affected by solvent and the doping anion's solubility in the solvent, and also by the history of electrochemical treatments in different electrolyte solutions. It is very interesting that NO3-doped polypyrrole can completely keep its conducting state (doped state) at a reasonably negative potential (eg -0.8 V vs. sce) in acetonitrile solutions.

ADVANCED ELECTROANALYTICAL CHEMISTRY IN CHINA .1. GENERAL ASPECT AND SOME METHODOLOGIES

The Research on Electroanalytical chemistry in China started mainly from the beginning of new China in 1949. It has already good basis and development nowadays. A review with references to the end of seventies has been published in "Reviews in Analytical Chemistry" 1) and in a book titled "Fifty years of Chinese Chemistry" edited by the Chinese Chemical Society in 1985 2). Since then more than thousand papers have been published, and it is impossible and also not necessary to describe all of them. This review only deals with the main progress of electroanalytical chemistry in China in recent years. Some new developed methodologies will be reviewed by S. Dong in the next article.

Selective and specific detection of sulfate-reducing bacteria using potentiometric stripping analysis

A fast, sensitive and reliable potentiometric stripping analysis (PSA) is described for the selective detection of the marine pathogenic sulfate-reducing bacterium (SRB). Desulforibrio caledoiensis. The chemical and electrochemical parameters that exert influence on the deposition and stripping of lead ion, such as deposition potential, deposition time and pH value were carefully studied. The concentration of SRB was determined in acetate buffer solution (pH 5.2) under the optimized condition (deposition potential of -1.3 V. deposition time of 250 s, ionic strength of 0.2 mol L-1 and oxidant mercury (II) concentration of 40 mg L-1). A linear relationship between the stripping response and the logarithm of the bacterial concentration was observed in the range of 2.3 x 10 to 2.3 x 10(7) cfu mL(-1). In addition, the potentiometric stripping technique gave a distinct response to the SRB, but had no obvious response to Escherichia coli. The measurement system has a potential for further applications and provides a facile and sample method for detection of pathogenic bacteria. (C) 2010 Elsevier B.V. All rights reserved.

Preparation of supported PtRu/C electrocatalyst for direct methanol fuel cells

In this work, high-surface supported PtRu/C were prepared with Ru(NO)(NO3)(3) and [Pt(H2NCH2CH2NH2)(2)]Cl-2 as the precursors and hydrogen as a reducing agent. XRD and TEM analyses showed that the PtRu/C catalysts with different loadings possessed small and homogeneous metal particles. Even at high metal loading (40 wt.% Pt, 20 wt.% Ru) the mean metal particle size is less than 4 nm. Meanwhile, the calculated Pt crystalline lattice parameter and Pt (220) peak position indicated that the geometric structure of Pt was modified by Ru atoms. Among the prepared catalysts, the lattice parameter of 40-20 wt.% PtRu/C contract most. Cyclic voltammetry (CV), chronoamperometry (CA), CO stripping and single direct methanol fuel cell tests jointly suggested that the 40-20 wt.% PtRu/C catalyst has the highest electrochemical activity for methanol oxidation. (c) 2004 Elsevier Ltd. All rights reserved.

Refractive changes after descemet stripping endothelial keratoplasty: a simplified mathematical model.

PURPOSE: To develop a mathematical model that can predict refractive changes after Descemet stripping endothelial keratoplasty (DSEK). METHODS: A mathematical formula based on the Gullstrand eye model was generated to estimate the change in refractive power of the eye after DSEK. This model was applied to four DSEK cases retrospectively, to compare measured and predicted refractive changes after DSEK. RESULTS: The refractive change after DSEK is determined by calculating the difference in the power of the eye before and after DSEK surgery. The power of the eye post-DSEK surgery can be calculated with modified Gullstrand eye model equations that incorporate the change in the posterior radius of curvature and change in the distance between the principal planes of the cornea and lens after DSEK. Analysis of this model suggests that the ratio of central to peripheral graft thickness (CP ratio) and central thickness can have significant effect on refractive change where smaller CP ratios and larger graft thicknesses result in larger hyperopic shifts. This model was applied to four patients, and the average predicted hyperopic shift in the overall power of the eye was calculated to be 0.83 D. This change reflected in a mean of 93% (range, 75%-110%) of patients' measured refractive shifts. CONCLUSIONS: This simplified DSEK mathematical model can be used as a first step for estimating the hyperopic shift after DSEK. Further studies are necessary to refine the validity of this model.

Cyclic voltammetry and spectroelectrochemical study of nickel and cobalt diphenyltetraazaannulene complexes

The absorption spectra. cyclic voltammetry and spectroelectrochemistry of [Ni(II)DPTAA] and [Co(II)DPTAA] (DPTAA = 6,13-diphenyldibenzo[b,i][1,4,8,11] tetraaza[14]annulene) complexes in DMF are reported in detail. The ligand oxidation is observed for [Ni(II)DPTAA] at +0.70 V vs. SCE whereas Ni2(+/+) occurs at - 1.60 V. For [Co(II)DPTAA], a ligand oxidation redox couple is seen at +0.56 V while the Co2+/+ and Co2+/3+ redox couples appear at -1.21 and +0.24 V, respectively. All observed redox couples are assigned to reversible one-electron processes on account of peak separations and scan-rate dependency. These processes were further investigated by spectroelectrochemistry for [Co(II)DPTAA]. For [Co(II)DPTAA], axial ligation of pyridine was found to shift the Co2+/3+ redox couple more negative. while the ligand oxidation was shifted to more positive potentials. From a spectrophotometric titration of [Co(II)DPTAA] with pyridine an equilibrium constant, K-f, was determined for the binding of pyridine to [Co(II)DPTAA]. This was found to be 10.2 dm(3) mol(-1), slightly lower than that of [Co(II)TAA], indicating the influence of the phenyl groups. From this value and shifts in the Co2+/3+ redox couple upon ligation, an equilibrium constant for the binding of pyridine to [Co(III)DPTAA], K'(f), was found to be 5.06 x 10(6) dm(3) mol(-1). (c) 2007 Elsevier B.V. All rights reserved.