title: Simple, Reversible, and Fast Modulation in Superwettability, Gradient, and Adsorption by Counterion Exchange on Self-Assembled Monolayer.
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.
authors.affiliation: Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
authors.forename: Josef
authors.initials: J
authors.lastname: Osicka
authors.affiliation: Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
authors.forename: Marketa
authors.initials: M
authors.lastname: Ilčiková
authors.affiliation: Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
authors.forename: Anton
authors.initials: A
authors.lastname: Popelka
authors.affiliation: Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Filip
authors.affiliation: Department of Glycobiotechnology, Institute of Chemistry, Slovak Academy of Sciences , Dubravská cesta 9, 842 36 Bratislava, Slovak Republic.
authors.forename: Tomas
authors.initials: T
authors.lastname: Bertok
authors.affiliation: Department of Glycobiotechnology, Institute of Chemistry, Slovak Academy of Sciences , Dubravská cesta 9, 842 36 Bratislava, Slovak Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Tkac
authors.affiliation: Center for Advanced Materials, Qatar University , P.O. Box 2713, Doha, Qatar.
authors.forename: Peter
authors.initials: P
authors.lastname: Kasak