Interfacial Density Profiles of Polar and Nonpolar Liquids at Hydrophobic Surfaces

Miaoqi Chu, Mitchell Miller, Pulak Dutta*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


A density-depleted region ("gap") is known to exist between water and hydrophobic surfaces. Using X-ray reflectivity, we have observed similar gaps between hydrophobic self-assembled monolayers (SAMs) and four other polar liquids. For these liquids and for water, the observed electron density depletion is nonzero and is in most cases slightly greater than the depletion attributable to the layer of hydrogen atoms at the SAM surface. On the other hand, the observed X-ray reflectivity from the interfaces between SAMs and three nonpolar liquids studied can be explained either without gaps or with smaller gaps. Thus, polar liquids (including but not limited to water) stand away from even the terminal hydrogen atoms at hydrophobic surfaces, while nonpolar liquids interpenetrate the terminal region. There is no consistent correlation between the sizes of the gaps and the liquid-SAM contact angles, the relative polarities of the polar liquids, or their bulk densities.

Original languageEnglish (US)
Pages (from-to)906-910
Number of pages5
Issue number4
StatePublished - Feb 4 2020

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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