| Abstract
| - Electroswitchable wetting of electrode surfaces modified with redox-active monolayers and thin filmsis described. Electrocatalytic and bioelectrocatalytic processes that are activated by the redox-active interfacesassociated with electrodes control the hydrophobic/hydrophilic properties of the surfaces, thus allowingthe probing of the chemical transformations by static contact angle measurements. A Prussian Blue filmassociated with an ITO electrode undergoes redox transformations between the hydrophilic reduced state,PB4-, the hydrophobic semioxidized state, PB0, and the hydrophilic fully oxidized state, PB3+. Contactangle measurements follow the reversible switching of the film between the three states. The oxidizedstate, PB3+, electrocatalyzes the oxidation of NADH, and thus, the ratio of PB3+/PB0 on the film interfaceupon the electrochemical oxidation of NADH is controlled by the cofactor concentration. This enablesfollowing the electrocatalyzed oxidation of NADH by static contact angle measurements. Similarly, thehydrophobic/hydrophilic properties of a naphthoquinone-functionalized polyethylenimine film are reversiblyelectroswitched by the reduction and oxidation of the film. In the reduced state of the film thenaphthohydroquinone units catalyze the reduction of O2, thus leading to a hydrophobic film that originatesfrom the high naphthoquinone/naphthohydroquinone ratio associated with the film. The hydrophobic/hydrophilic properties of an Au electrode modified with a ferrocene monolayer are electroswitched betweena hydrophilic state in the presence of the ferrocenylium (Fc+) oxidized monolayer and a hydrophobic statein the presence of the ferrocene (Fc) monolayer configuration. The ferrocenylium monolayer activates thebioelectrocatalyzed oxidation of glucose in the presence of glucose oxidase. The bioelectrocatalyzed oxidationof glucose leads to the control of the Fc+/Fc ratio associated with the monolayer by the glucose concentrationin the system. This enables following the bioelectrocatalytic oxidation of glucose by static contact anglemeasurements.
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