Charge transfer as a ubiquitous mechanism in determining the negative charge at hydrophobic interfaces

Emiliano Poli, Kwang H. Jong, Ali Hassanali

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


The origin of the apparent negative charge at hydrophobic–water interfaces has fueled debates in the physical chemistry community for decades. The most common interpretation given to explain this observation is that negatively charged hydroxide ions (OH–) bind strongly to the interfaces. Using first principles calculations of extended air–water and oil–water interfaces, we unravel a mechanism that does not require the presence of OH–. Small amounts of charge transfer along hydrogen bonds and asymmetries in the hydrogen bond network due to topological defects can lead to the accumulation of negative surface charge at both interfaces. For water near oil, some spillage of electron density into the oil phase is also observed. The computed surface charge densities at both interfaces is approximately −0.015e∕nm2 in agreement with electrophoretic experiments. We also show, using an energy decomposition analysis, that the electronic origin of this phenomena is rooted in a collective polarization/charge transfer effect.
Original languageEnglish (US)
JournalNature Communications
Issue number1
StatePublished - Feb 14 2020
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2022-06-14
Acknowledgements: E.P. and A.H. acknowledge the support from KAUST (Shaheen II project-k1263). E.P. and A.H. acknowledge Himashu Mishra for the useful discussions and insightful help provided during the work.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology
  • General Chemistry
  • General Physics and Astronomy


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