Interactions between hydrophilic and hydrophobic surfaces on microscopic scale and the influence of air bubbles as observed by scanning force microscopy in aqueous and alcoholic mediums

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Papastavrou, Georg ; Akari, S. ; Möhwald, Helmuth:
Interactions between hydrophilic and hydrophobic surfaces on microscopic scale and the influence of air bubbles as observed by scanning force microscopy in aqueous and alcoholic mediums.
In: Europhysics Letters. Bd. 52 (2000) Heft 5 . - S. 551-556.
ISSN 0295-5075
DOI: https://doi.org/10.1209/epl/i2000-00472-2

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Abstract

In the present study interactions between hydrophilic and hydrophobic surfaces were studied on a microscopic scale by using scanning force microscopy (SFM). Gold-coated surfaces were chemically modified to be hydrophobic or hydrophilic by self-assembly monolayers based on thiols with different end-groups (COOH, CH3). The adhesion forces between hydrophilic tips and hydrophilic or hydrophobic surfaces were measured in water/ethanol mixtures by recording force-distance curves. The measurements in water/ethanol mixtures short an increase of the adhesion forces due to the increase of the water content. The observed interactions are of short range within few nm. In some force-distance curves with hydrophobic tips a stepping in the retracting part was observed which could be attributed to air bubbles in the vicinity of the tip-surface junction.