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Understanding Depletion Induced Like-Charge Attraction from Self-Consistent Field Model

Published online by Cambridge University Press:  03 May 2017

Pei Liu*
Affiliation:
School of Mathematical Sciences and Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
Manman Ma*
Affiliation:
School of Mathematical Sciences and Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
Zhenli Xu*
Affiliation:
School of Mathematical Sciences and Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, P.R. ChinaMoE Key Lab of Scientific and Engineering Computing, Shanghai Jiao Tong University, Shanghai 200240, P.R. China
*
*Corresponding author. Email addresses:hgliupei1990@sjtu.edu.cn (P. Liu), mmm@sjtu.edu.cn (M. Ma), xuzl@sjtu.edu.cn (Z. Xu)
*Corresponding author. Email addresses:hgliupei1990@sjtu.edu.cn (P. Liu), mmm@sjtu.edu.cn (M. Ma), xuzl@sjtu.edu.cn (Z. Xu)
*Corresponding author. Email addresses:hgliupei1990@sjtu.edu.cn (P. Liu), mmm@sjtu.edu.cn (M. Ma), xuzl@sjtu.edu.cn (Z. Xu)

Abstract

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The interaction force between likely charged particles/surfaces is usually repulsive due to the Coulomb interaction. However, the counterintuitive like-charge attraction in electrolytes has been frequently observed in experiments, which has been theoretically debated for a long time. It is widely known that the mean field Poisson-Boltzmann theory cannot explain and predict this anomalous feature since it ignores many-body properties. In this paper, we develop efficient algorithm and perform the force calculation between two interfaces using a set of self-consistent equations which properly takes into account the electrostatic correlation and the dielectric-boundary effects. By solving the equations and calculating the pressure with the Debye-charging process, we show that the self-consistent equations could be used to study the attraction between like-charge surfaces from weak-coupling to mediate-coupling regimes, and that the attraction is due to the electrostatics-driven entropic force which is significantly enhanced by the dielectric depletion of mobile ions. A systematic investigation shows that the interaction forces can be tuned by material permittivity, ionic size and valence, and salt concentration, and that the like-charge attraction exists only for specific regime of these parameters.

Information

Type
Research Article
Copyright
Copyright © Global-Science Press 2017