Impurity effects at hydrophobic surfaces

Yuki Uematsu, Douwe Jan Bonthuis, Roland R. Netz*

*Corresponding author for this work

Research output: Contribution to journalReview article

Abstract

The effective charge of hydrophobic surfaces and in particular of the air–water interface is a crucial parameter for electrochemistry, colloidal chemistry and interfacial science, but different experiments give conflicting estimates. Zeta-potential and disjoining-pressure measurements point to a strongly negative surface charge, often interpreted as being due to adsorbing hydroxide ions. In contrast, surface tension measurements of acids and bases suggest the hydronium ion to be surface active, in agreement with some surface-specific non-linear spectroscopy results. The air–electrolyte interfacial tension exhibits a characteristic minimum at millimolar electrolyte concentration for all salts, the so-called Jones–Ray effect, which points to competitive adsorption mechanisms present in dilute electrolyte solutions. We show that all these puzzling experimental findings can be explained by the presence of trace amounts of surface-active charged impurities, most likely anionic surfactants.

Original languageEnglish
Pages (from-to)166-173
Number of pages8
JournalCurrent Opinion in Electrochemistry
Volume13
DOIs
Publication statusPublished - 1 Feb 2019
Externally publishedYes

Keywords

  • Disjoining pressure
  • Hydrophobic surfaces
  • Impurities in water
  • Jones-Ray effect
  • Surface tension
  • Zeta potential

ASJC Scopus subject areas

  • Analytical Chemistry
  • Electrochemistry

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