Tuning the hydrophobicity of mica surfaces by hyperthermal Ar ion irradiation

Adrian Keller, Monika Fritzsche, Ryosuke Ogaki, Ilko Bald, Stefan Facsko, Mingdong Dong, Peter Kingshott, Flemming Besenbacher

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    Abstract

    The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K(+) ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle >80° is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity.
    Original languageEnglish
    JournalJournal of Chemical Physics
    Volume134
    Issue10
    Pages (from-to)104705
    ISSN0021-9606
    DOIs
    Publication statusPublished - 14 Mar 2011

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