Ion Channel (mimetic) Sensors : Mechanism of Charge Propagation through Thiol-, Protein- and Dendrimer-Modified Electrodes

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Title: Ion Channel (mimetic) Sensors : Mechanism of Charge Propagation through Thiol-, Protein- and Dendrimer-Modified Electrodes
Authors: Degefa, Tesfaye Hailu
Thesis advisor: Prof. Dr. Lorenz Walder
Thesis referee: Prof. Philippe Buhlmann
Abstract: The mechanism of ion channel (mimetic) sensors (ICSs) consisting of (poly)electrolyte type alkane thiol, protein or dendrimer self assembled monolayers (SAMs) at gold electrodes as a sensing layer and highly charged redox-active marker ions in solution was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and rotating disk voltammetry (RDV) in the presence of a series of analytes, i.e, suppressor and enhancer ions, leading to the following general statements: (i) electrostatic binding of marker ions to the sensing layer is a prerequisite for an electrochemical current and (ii) charge propagation through the layer consists of electron hopping between surface-confined marker ions and solution born marker ions. It is further shown that there exists (iii) competition between equally charged ions for coordination sites at the oppositely charged sensing layer. An apparent charge inversion (iv) by surface confinement of multiple charged counter ions occurs. Thereby an existing electron transfer (ET) path can be cut or a new one can be induced. Build up of a second layer of multiple charged electroactive ions (v) can take place on top of the charge inverted layer. Competing ET (vi) through the inner and outer redox layer can take place. In addition to fundamental insight into the mechanism of charge propagation, valuable information for the design, optimization, and tailoring of new biosensors based on the ICS concept, the possibilities of exploiting layer-by-layer electrostatic SAMs and dendrimer-DNA interaction for bioanalytical applications are demonstrated by the current findings.
Subject Keywords: Self assembled monolayer; Marker ions; Electrostatic interactions; Electron transfer catalysis; Ion channel (mimetic) sensors
Issue Date: 22-Dec-2005
Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB05 - E-Dissertationen

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