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Updated: Mar 21, 2026

Antifouling Self-assembled Monolayers on Microelectrodes for Patterning Biomolecules
Published on: August 25, 2009
Simple, Reversible, and Fast Modulation in Superwettability, Gradient, and Adsorption by Counterion Exchange on
Josef Osicka1, Marketa Ilčiková1, Anton Popelka1
1Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
Abstract:
A simple fabrication method for preparation of surfaces able to switch from superhydrophobic to superhydrophilic state in a reversible and fast way is described. A self-assembled monolayer (SAM) consisting of quaternary ammonium group with aliphatic tail bearing terminal thiol functionality was created on gold nano/microstructured and gold planar surfaces, respectively. A rough nano/microstructured surface was prepared by galvanic reaction on a silicon wafer. The reversible counterion exchange on the rough surface resulted in a switchable contact angle between <5° and 151°. The prewetted rough surface with Cl(-) as a counterion possesses a superoleophobic underwater character. The kinetics of counterion exchanges suggests a long hydration process and strong electron ion pairing between quaternary ammonium group and perfluorooctanoate counterion. Moreover, a wettability gradient from superhydrophobic to superhydrophilic can be formed on the modified rough gold surface in a robust and simple way by passive incubation of the substrate in a counterion solution and controlled by ionic strength. Furthermore, adsorption of gold nanoparticles to modified plain gold surface can be controlled to a high extent by counterions present on the SAM layer.
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