Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 12: POSTER Colloids, Nanoparticles and Self-Organizing Systems
CPP 12.1: Poster
Tuesday, March 28, 2006, 17:00–19:00, P3
Water density reduction at hydrophobic interfaces: a neutron reflectometry study — •Marco Maccarini1, Michael Himmelhaus1, Roland Steitz2, Maximilian Wolff3, and Michael Grunze1 — 1Institut für Ang. Physikalische Chemie, Universität Heidelberg, Germany — 2Hahn-Meitner-Institut, Berlin, Germany — 3Institut Laue-Langevin, Grenoble, France
A close relationship exists between the structure of a liquid in the vicinity of a surface and the solvation force appearing between two surfaces immersed in the liquid. This relationship has important implications in the case of hydrophobic surfaces and water since the resulting force, the hydrophobic interaction, is responsible for key biological phenomena such as protein folding, self-assembling, colloids stability and membrane fusion. The origin of this interaction has still a number of unexplained features because the structure and the conformation of water molecules in the vicinity of hydrophobic surfaces are not fully understood. Theoretical studies (Lum 1999, Mamatkulov 2004) predicted a depletion layer, i.e. a reduced water density, near the hydrophobic surface/water interface. This extends to a thickness in the order of nm into the bulk water and is thermodynamically less stable than the vapor phase. In order to clarify the extension of the depletion layer and its dependence on some parameters like temperature, pH and electrolyte concentration, we performed neutron reflectometry on hydrophobic surfaces formed by the adsorption of alkanethiols self assembling monolayers (SAM) on gold surfaces in contact with water and non polar solvents.