title: High-resolution in situ x-ray study of the hydrophobic gap at the water-octadecyl-trichlorosilane interface.
abstract: The knowledge of the microscopic structure of water at interfaces is essential for the understanding of interfacial phenomena in numerous natural and technological environments. To study deeply buried liquid water-solid interfaces, high-energy x-ray reflectivity measurements have been performed. Silicon wafers, functionalized by a self-assembled monolayer of octadecyl-trichlorosilane, provide strongly hydrophobic substrates. We show interfacial density profiles with angstrom resolution near the solid-liquid interface of water in contact with an octadecyl-trichlorosilane layer. The experimental data provide clear evidence for the existence of a hydrophobic gap on the molecular scale with an integrated density deficit rhod = 1.1 A g cm(-3) at the solid-water interface. In addition, measurements on the influence of gases (Ar, Xe, Kr, N(2), O(2), CO, and CO(2)) and HCl, dissolved in the water, have been performed. No effect on the hydrophobic water gap was found.
authors.affiliation: Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Mezger
authors.forename: Harald
authors.initials: H
authors.lastname: Reichert
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schöder
authors.forename: John
authors.initials: J
authors.lastname: Okasinski
authors.forename: Heiko
authors.initials: H
authors.lastname: Schröder
authors.forename: Helmut
authors.initials: H
authors.lastname: Dosch
authors.forename: Dennis
authors.initials: D
authors.lastname: Palms
authors.forename: John
authors.initials: J
authors.lastname: Ralston
authors.forename: Veijo
authors.initials: V
authors.lastname: Honkimäki