1,674 research outputs found
Electrocatalysis and Amperometric Detection of Alditols and Sugars at a Gold-Nickel Composite Electrode in Anion-Exchange Chromatography.
No full textAbstract: A novel Au-Ni composite electrode prepared by cathodic precipitation/deposition of nickel hydroxide on the gold surface was characterised. The resulting composite electrode was evaluated as an amperometric sensor in flow injection analysis and anion-exchange chromatography for the quantitation of alditols and simple carbohydrates. Constant potential detection at +0.6V vs Ag/AgCl and a pulsed detection mode were employed, and their applicability and usefulness discussed. The detection Limits (S/N = 3) for all investigated compounds, in both modes of detection, ranged between 1.5 and 7.5 pmol injected. Linear dynamic ranges spanned over four and three orders of magnitude when the composite electrode was used in the DC or pulsed mode. The main advantage of the Au-Ni composite electrode is that detection selectivity can be tailored by the choice of the detection mode and by the polarisation potential. As an example, we show how to detect common carbohydrates in tea powder using the constant potential detection mode. (C) 1999 Elsevier Science B.V. All rights reserved
STUDY OF A NICKEL-CATALYZED GLASSY-CARBON ELECTRODE FOR DETECTION OF CARBOHYDRATES IN LIQUID-CHROMATOGRAPHY AND FLOW-INJECTION ANALYSIS
No full textAmperometric Determination of Underivatised Amino Acids at a Nickel-Modified Gold Electrode
No full textDETECTION OF HYDRAZINE AND ITS DERIVATIVES AT A RUTHENIUM/NAFION CHEMICALLY MODIFIED ELECTRODE.
No full textElectrochemical codeposition and spectroscopic characterization of copper-thallium oxide films prepared in aqueous basic solutions
No full textComposite thallium-copper (Cu-Tl) oxide films supported on glassy carbon were prepared by electrodeposition from citrate alkaline solutions. The resulting Cu-Tl deposits were characterized by cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. Upon deposition the electrochemical activity of copper was evaluated in NaOH solutions as a function of thallium and citrate concentrations along with sweep potential limits. The electrochemical activity of copper appears to be enhanced by the codeposition of thallium oxide species. The high activity of copper, in the presence of thallium oxides, may be considered as mainly due to a marked augment of the active surface area of the electrode material. The XPS depth profiling reveals an almost homogeneous distribution of the Cu/Tl atomic ratio within the deposited films, with a slight enrichment of copper oxide species on the surface electrode relative to bulk; an average chemical composition of Cu45Tl55 was established
Electrochemical Preparation of a Composite Gold-Cobalt Electrode and its Electrocatalytic Activity in Alkaline Medium
No full textAbstract: A chemically modified electrode composed of cobalt(III) oxyhydroxide film dispersed on the gold substrate (Au-Co) was characterised by cyclic voltammetry. Electrochemical deposition of the cobalt film was accomplished by cycling the potential between 0.0 V and 1.1 V (vs. saturated calomel electrode (SCE)) in 0.1 M acetate solution (at pH 7.3) containing 10 mM CoCl2. The effects of several experimental parameters (pH, applied potentials, etc.) on the film formation and growth were evaluated. The electrochemical behaviour of the Au-Co composite electrode was investigated in alkaline medium. The film appears uniform and compact and shows good electrical conductivity and electrochemical activity towards the oxidation of several scarcely electroactive organic molecules. The concomitant presence on the electrode surface of both active catalysts leads to a wide range of potential applications where a significant electrochemical activity towards the electrooxidation of several classes of organic compounds is observed. (C) 1999 Elsevier Science Ltd. All rights reserved
Study of Sugar Acids Separation by HPAEC-PAD Using Alkaline Eluents Spiked with Ba2+, Sr2+, or Ca2+ as Acetate or Nitrate Salts
No full textAnodic Electrodeposition of Conducting Cobalt Oxyhydroxide Films on a Gold Surface. XPS Study and Electrochemical Behaviour in Neutral and Alkaline Solution
No full textAbstract: A novel chemically modified electrode prepared by anodic electrodeposition of cobalt (III) film on the gold electrode substrate (Au-Co) was characterised by cyclic voltammetry and XPS techniques in both neutral and alkaline medium. Cobalt oxyhydroxide film was deposited by cycling the potential between 0.0 and 1.1 V versus SCE in 0.1 M sodium acetate solutions containing 10 mM CoCl2. The electrocatalytic properties of the Au-Co electrode were investigated in alkaline medium using glucose as a model compound. A comparative XPS study of bare gold, bare cobalt and Au-Co electrodes after electrochemical treatment in neutral and alkaline solutions has been carried out. A detailed XPS analysis of the Au4f(7.2), Co2p(3.2), O1s and C1s regions was performed to check the chemical composition of the Au-Co electrode upon electrochemical treatments. Film deposition is attributed to growth of conducting and compact CoOOH oxyhydroxide with significant insertion of carbonyl groups within the electrodeposited layer. The prolonged electrochemical treatment in alkaline medium produces a good stabilization of the Co-III oxyhydroxide film, with a dominant O1s feature at about 532.4 eV of BE corresponding to a non-stoichiometric surface oxygen. The absence of CoO species proves good conducting properties of the cobalt film and the absence of any passivation effects on the catalytic performance. (C) 1999 Elsevier Science S.A. All rights reserved
DFT study of the interaction free energy of π-π complexes of fullerenes with buckybowls and viologen dimers
No full textWe present a theoretical investigation, by means of DFT protocols, of the complexation thermodynamics of (i) complexes of C70 and C 60 fullerenes with bowl-shaped hexabenzocoronene derivatives and (ii) complexes of C60 with viologen dimers. The recent functionals of the M06 family, accounting for π-π interactions to a good level of approximation, have been used to calculate the interaction free energies. For the former complexes, the good agreement between the calculated results and the experimental data confirms the reliability of the protocol used. On these grounds, we then checked the stability of a series of complexes of C 60 with some viologen dimers, 1BPnBP1 (n = 6-9), where two N-methylated bipyridinium units are linked by an alkyl chain of variable length, acting as molecular tweezers. Both forms of the viologen cores, that is the cation (each core doubly charged) and the reduced neutral form, were considered. For a suitable chain length a free energy gain upon complexation is predicted for the neutral form while the complexation of C60 by the cationic form is disfavoured mainly for entropic reasons. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique
Caratterizzazione di un elettrodo oro-nichel per la determinazione amperometrica di carboidrati e amminoacidi previa separazione cromatografica a scambio anionico
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