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Impact of surface charges on the solvation forces in confined colloidal solutions

Grandner, S. ; Zeng, Y. ; Klitzing, R. von ; Klapp, S. H. L. (2009):
Impact of surface charges on the solvation forces in confined colloidal solutions.
In: Journal of Chemical Physics, 131 (15), AIP Publishing, ISSN 0021-9606,
DOI: 10.1063/1.3246844,
[Article]

Abstract

Combining computer simulations and experiments we address the impact of charged surfaces on the solvation forces of a confined, charged colloidal suspension (slit-pore geometry). Investigations based on the colloidal-probe atomic-force-microscope technique indicate that an increase in surface charges markedly enhances the oscillations of the force in terms of their amplitude. To understand this effect on a theoretical level we perform grand-canonical Monte-Carlo simulations (GCMC) of a coarse-grained model system. It turns out that various established approaches of the interaction between a charged colloid and a charged wall, such as linearized Poisson–Boltzmann (PB) theory involving the bulk screening length, do not reproduce the experimental observations. We thus introduce a modified PB potential with a space-dependent screening parameter. The latter takes into account, in an approximate way, the fact that the charged walls release additional (wall) counterions which accumulate in a thin layer at the surface(s). The resulting, still purely repulsive fluid-wall potential displays a nonmonotonic behavior as function of the surface potential with respect to the strength and range of repulsion. GCMC simulations based on this potential reproduce the experimentally observed charge-induced enhancement in the force oscillations. We also show, both by experiment and by simulations, that the asymptotic wave- and decay length of the oscillating force do not change with the wall charge, in agreement with predictions from density functional theory.

Item Type: Article
Erschienen: 2009
Creators: Grandner, S. ; Zeng, Y. ; Klitzing, R. von ; Klapp, S. H. L.
Title: Impact of surface charges on the solvation forces in confined colloidal solutions
Language: English
Abstract:

Combining computer simulations and experiments we address the impact of charged surfaces on the solvation forces of a confined, charged colloidal suspension (slit-pore geometry). Investigations based on the colloidal-probe atomic-force-microscope technique indicate that an increase in surface charges markedly enhances the oscillations of the force in terms of their amplitude. To understand this effect on a theoretical level we perform grand-canonical Monte-Carlo simulations (GCMC) of a coarse-grained model system. It turns out that various established approaches of the interaction between a charged colloid and a charged wall, such as linearized Poisson–Boltzmann (PB) theory involving the bulk screening length, do not reproduce the experimental observations. We thus introduce a modified PB potential with a space-dependent screening parameter. The latter takes into account, in an approximate way, the fact that the charged walls release additional (wall) counterions which accumulate in a thin layer at the surface(s). The resulting, still purely repulsive fluid-wall potential displays a nonmonotonic behavior as function of the surface potential with respect to the strength and range of repulsion. GCMC simulations based on this potential reproduce the experimentally observed charge-induced enhancement in the force oscillations. We also show, both by experiment and by simulations, that the asymptotic wave- and decay length of the oscillating force do not change with the wall charge, in agreement with predictions from density functional theory.

Journal or Publication Title: Journal of Chemical Physics
Volume of the journal: 131
Issue Number: 15
Publisher: AIP Publishing
Divisions: 05 Department of Physics
05 Department of Physics > Institute for condensed matter physics (2021 merged in Institute for Condensed Matter Physics)
Date Deposited: 28 Apr 2017 11:05
DOI: 10.1063/1.3246844
Additional Information:

Art.No.: 154702; Erstveröffentlichung

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