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  • Polymer and Materials Science  (3)
  • Key words: Microstructuring; monolayer patterning; self-assembled monolayers; scanning electrochemical microscopy; SECM.  (1)
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  • 1
    ISSN: 1436-5073
    Keywords: Key words: Microstructuring; monolayer patterning; self-assembled monolayers; scanning electrochemical microscopy; SECM.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract.  Lateral structures of bare gold within self-assembled monolayers (SAMs) of gold alkanethiolates were created by electrochemical desorption in the direct mode of the scanning electrochemical microscope (SECM). The ultramicroelectrode (UME) of the SECM was positioned 10–20 μm above the surface and used as the auxiliary electrode in a three electrode cell with the SAM-coated Au electrode as working electrode. The microscopic auxiliary electrode causes an inhomogeneous electric field above the macroscopic gold electrode and limits the total current. As a consequence only thiols located directly beneath the UME are affected by the desorption procedure. Sample regions from which the SAM had been removed were imaged in the SECM feedback mode or, after galvanic Cu deposition, by scanning electron microscopy (SEM) and optical microscopy (after sulfidisation of Cu). The influence of hydrocarbon chain length, protection of the SAM by an additional layer of n-octanol and the use of alternating current were investigated in order to decrease the size of the bare surface areas and to enhance their edge definition. In particular the use of alternating current led to feature sizes of 1.2 times the UME diameter which represents an advance with regard to 2–3 UME diameters reported earlier.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1040-0397
    Keywords: Self-assembled monolayers ; Alkanethiolate ; Gold surface ; Monolayer patterning ; Scanning electrochemical microscopy ; SECM ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrochemically induced localized desorption of self-assembled dodecylthiolate monolayers from a macroscopic Au electrode was performed using a scanning electrochemical microscope (SECM). The microelectrode of the SECM is operated as auxiliary electrode and moved in close proximity to the monolayer-covered gold surface, thereby restricting electrochemical reactions occurring at the macroscopic gold surface to a region perpendicular beneath the auxiliary microelectrode. Subsequently, the obtained laterally-structured monolayers have been imaged using the feedback mode of the SECM. High feedback currents occur over regions from which the alkanethiolate monolayer was locally desorbed while low currents are measured over the intact layer. The electrochemically induced desorption of alkanethiolate monolayers was laterally restricted to regions which are approximately 2-3 times larger in diameter than the diameter of the microelectrode used in the desorption step. The desorption protocol has been optimized to obtain renewed gold surfaces of defined geometry. First evidence was obtained that re-adsorption of functionalized thiols onto these renewed and laterally structured gold surfaces, which are surrounded by the densely packed nonfunctionalized monolayer, may open routes for the fabrication of miniaturized integrated sensors and sensor arrays.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 143-146 
    ISSN: 1040-0397
    Keywords: Redox mediators ; Immunoglobulin G ; Polyvinyl ferrocene ; Butyl ferrocene ; lmmunosensor model ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a step towards a voltammetric immunoassay with antibodies directly attached onto the electrode surface, the mediated oxidation of a redox active label has been investigated with a model system. Butyl ferrocene served as a model for the mediator and was coimmobilized onto a glassy carbon electrode within a layer of bovine immunoglobulin G, which mimiked the antibody. An overlaid polyvinyl ferrocene layer was employed to simulate a ferrocene-tagged high molecular weight antigen bound to the immobilized antibodies. A mediated electron transfer could only be demonstrated with butyl ferrocene as mediator, whereas other compounds failed to support an electron transfer between the polyvinyl ferrocene layer and the electrode through the layer of immunoglobulin.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 449-453 
    ISSN: 1040-0397
    Keywords: Adsorption ; Ubiquinones ; Inhibition ; Stationary mercury electrode ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Adsorption isotherms of the ubiquinones UQ4, UQ6, UQ9 and UQ10 have been determined by two independent voltammetric techniques at the stationary mercury/solution interface. While the redox behavior is essentially the same for all homologues investigated, the molar free enthalpy of adsorption ΔAG increases steadily with the number of isoprenic units from UQ4 to UQ10. In case of UQ10, the experiments have been carried out with three different potentiostatic systems. This allows one to estimate the accuracy of the methods which are direct ones and do not require calibration.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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