Density Depletion at Solid-Liquid Interfaces: a Neutron Reflectivity Study

článek v časopise - ostatní, Jost

angličtina

Neutron reflectivity experiments conducted on self-assembled monolayers (SAMs) against polar (water) and nonpolar (organic) liquid phases reveal further evidence for a density reduction at hydrophobic-hydrophilic interfaces. The density depletion is found at the interface between hydrophobic dodecanethiol (C12) and hexadecanethiol (C16) SAMs and water and also between hydrophilic SAMs (C12/C11OH) and nonpolar fluids. The results show that the density deficit of a fluid in the boundary layer is not unique to aqueous solid-liquid interfaces but is more general and correlated with the affinity of the liquid to the solid surface. In water the variation of pH has only minor influence, while different electrolytes taken from the Hofmeister series seem to increase the depletion. On hydrophobic SAMs an increase in density depletion with temperature was observed, in agreement with Monte Carlo simulations performed on corresponding model systems. The increase in the water density depletion layer is governed by two effects: the surface energy difference between water and the substrate and the chemical potential of the aqueous phase.

SELF-ASSEMBLED MONOLAYERS; UNITED-ATOM DESCRIPTION; SURFACE FREE-ENERGY; HYDROPHOBIC SURFACES; WATER-STRUCTURE; TRANSFERABLE POTENTIALS; ACTIVITY-COEFFICIENTS; COMPUTER-SIMULATION; PHASE-EQUILIBRIA; MONTE-CARLO

Maccarini, M, Steitz, R., Himmelmaus, F., Fick, M., Tatur, S., Wolff, M., Grunze, M., Janeček, J., Netz, R.R.

2007

16. 1. 2007

ACS

Washington DC USA

0743-7463

Langmuir

23

2

Spojené státy americké

598

608

11