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  • Chemistry  (4)
  • Modified electrodes  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Non-linear least squares refinement with constraints. Evaluation through curve fitting on emulated XPS-like spectra and application to the analysis of carbon fibres (1994)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 8 (1994), S. 221-239 
    Details
    ISSN: 0886-9383
    Keywords: Fitting ; Non-linear ; Least squares ; Refinement ; Constraints ; MSE ; Confidence ; C ls ; XPS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A non-linear least squares iterative refinement has been implemented which shows high performance on a multiple-peak spectrum including baseline or background. Constraints as well as links within a range are introduced to drive the mathematical optimization: each peak parameter (i.e. height, position, Gaussian/Lorentzian mixing ratio and HWHM on both left and right sides) has assigned to it an allowed range of variation and can be strained to be correlated with other parameters belonging either to the same peak (symmetrical peaks) or to other peaks (doublets, triplets, etc.). Peak shapes typical of XP spectra are used and applications in the field of XPS are discussed. Through emulated curves with Poisson distributed noise, the accuracy and precision of back-calculated (refined) parameters have been estimated. Moreover, a confidence level calculated from X2 and degrees of freedom has been suggested to check the overall fitting of experimental curves where the signal-to-noise ratio is a priori unknown. An application to real C ls XP spectra is described as an example and a list of suggestions is given to match operator requirements. Finally, features of NLLSRC are discussed with respect to other approaches.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180080305
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    XPS, SEM and electrochemical characterization of a platinum-based glassy carbon modified electrode. Electrocatalytic oxidation of ethanol in acidic medium (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 447-453 
    Details
    ISSN: 1040-0397
    Keywords: Modified electrodes ; Electrocatalysis ; Platinum deposition ; Ethanol ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A platinum-based chemically modified glassy carbon electrode (Pt-CME) was characterized in acidic medium by X-ray photoelectron spectroscopy, scanning electron microscopy and electrochemical techniques. A uniform distribution of platinum microparticles of different form and size (hexagonal, grain-like and globular) was present on the surface of glassy carbon. The chemical species present on the electrode surface changed upon polarization. At higher potential values (1.5 V) species such Pt(OH)2, Pt(OH)ads and Pt(OH)4 formed at lower potential values were transformed into PtO, PtOads and PtO2 respectively. A few aspects of the electrooxidation of ethanol in acidic medium were investigated on the Pt-CME described.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140080509
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Study of a cobalt-based surface modified glassy carbon electrode: Electrocatalytic oxidation of sugars and alditols (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 305-311 
    Details
    ISSN: 1040-0397
    Keywords: Electrocatalysis ; Sugars ; Cobalt ; Modified electrodes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sugars and alditols undergo an electrocatalytic oxidation in alkaline solution at cobalt-oxide-based glassy carbon (Co/GC) electrodes. The catalytic deposit was investigated by cyclic voltammetry and scanning electron microscopy (SEM). It is pointed out that, at relatively low coverage of cobalt, two main redox processes, CoII → CoIII and CoIII → CoIV, are observed in 0.2 M NaOH. The redox behavior of the Co/GC electrode is strongly dependent on hydroxide ion concentration, and no electrocatalytic activity is observed at pH lower than 11.5. Under voltammetric conditions the modified electrode exhibits a non-Nernstian potential/pH shift (-88 ± 3 mV per pH unit). A reasonable explanation of the E/pH behavior in alkaline solution is given and an oxidation mechanism of CoII to CoIII is proposed in terms of hydrous cobalt oxides. No detrimental effects on the electrocatalytic oxidation of polyhydric compounds are observed in the presence of high acetonitrile concentrations (up to 40%). Inspection by SEM of the cobalt-based deposit evidenced the presence of grain-like microcrystallites on the glassy carbon surface.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070402
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the nickel-based chemically modified electrode obtained by electrochemical deposition of an NiII-tetramethyl-dibenzo-tetraaza [14] annulene complex. Redox catalysis of carbohydrates in alkaline solutions. II (1995)
    Weinheim : Wiley-Blackwell
    Electroanalysis 7 (1995), S. 435-441 
    Details
    ISSN: 1040-0397
    Keywords: Electrocatalysis ; Carbohydrates ; Electropolymerization ; Nickel ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical treatment of an electropolymerized (NiIIL)n thin film (where L represents 5,7,12,14-tetramethyl-dibenzo[b,i]-1,4,8,11-tetraaza [14] annulene) gives rise to a nickel-based catalytic deposit on conducting substrates [glassy carbon (GC), platinum, or gold electrodes], which shows strong similarities to the nickel hydroxide electrode. The effect of potential cycling on surface composition, chemical status, and morphology of this nickel-based chemically modified electrode (Ni-CME) has been investigated by cyclic voltammetry (CV) [1], X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy. XPS analysis was very useful for characterizing the chemical changes in the nickel coordination caused by electrochemical treatments in alkaline solution. The featureless surface of the as-prepared GC/(NiII)Ln, film compared with the fractal nature of the GC/Ni-CME was revealed by electron micrographs. The Ni- CME exhibits high electrocatalytic activity towards the oxidation of carbohydrates in alkaline solution. The electrooxidation capability of the Ni-CME is highlighted by the amperometric detection of sugars after anion-exchange liquid chromatographic separations with alkaline mobile phases.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140070506
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    Paper (German National Licenses)
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