Electrical conductance of hydrophobic membranes or what happens below the surface

Ivan Vlassiouk, Fabian Rios, Sean A. Vail, Devens Gust, Sergei Smirnov

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Nanoporous alumina membranes rendered hydrophobic by surface modification via covalent attachment of hydrocarbon or fluorocarbon chains conduct electricity via surface even when the pores are not filled with electrolyte. The resistance is many orders of magnitude higher than for electrolyte-filled membranes and does not depend on the electrolyte concentration or pH, but it does depend on the type of hydrophobic monolayer and its density. The corresponding surface resistance varies from greater than 10 18 Ω per square to less than 3 × 10 9 Ω per square. When the hydrophobic monolayer contains a small proportion of photoactive spiropyran that is insufficient to switch the surface to hydrophilic after spiropyran photoisomerization to the merocyanine form, the membrane resistance also becomes light-dependent with a reversible increase of surface resistance by as much as 15%. Surface conduction is ascribed to hydration and ionization of the alumina surface hydroxyls and the ionizable groups of the hydrophobic surface modifiers.

Original languageEnglish (US)
Pages (from-to)7784-7792
Number of pages9
Issue number14
StatePublished - Jul 3 2007

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry


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