title: The orientation and charge of water at the hydrophobic oil droplet-water interface.
abstract: We established the charge and structure of the oil/water interface by combining ζ-potential measurements, sum frequency scattering (SFS) and molecular dynamics simulations. The SFS experiments show that the orientation of water molecules can be followed on the oil droplet/water interface. The average water orientation on a neat oil droplet/water interface is the same as the water orientation on a negatively charged interface. pH dependent experiments show, however, that there is no sign of selective adsorption of hydroxide ions. Molecular dynamics simulations, both with and without intermolecular charge transfer, show that the balance of accepting and donating hydrogen bonds is broken in the interfacial layer, leading to surface charging. This can account for the negative surface charge that is found in experiments.
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Robert
authors.initials: R
authors.lastname: Vácha
authors.forename: Steven W
authors.initials: SW
authors.lastname: Rick
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
authors.forename: Alex G F
authors.initials: AG
authors.lastname: de Beer
authors.forename: Hilton B
authors.initials: HB
authors.lastname: de Aguiar
authors.forename: Jean-Sebastien
authors.initials: JS
authors.lastname: Samson
authors.forename: Sylvie
authors.initials: S
authors.lastname: Roke
mesh_terms: D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D009821:Oils / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D009821:Oils; D014867:Water; D006859:Hydrogen; D010100:Oxygen