Depletion forces due to image charges near dielectric discontinuities

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Curtis, Robin A. and Lue, Leo (2015) Depletion forces due to image charges near dielectric discontinuities. Current Opinion in Colloid and Interface Science, 20 (1). pp. 19-23. ISSN 1359-0294 (https://doi.org/10.1016/j.cocis.2014.12.001)

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Abstract

The depletion force is an eective inter-particle attractive interaction that is entropically driven by the exclusion of co-solvent molecules. For large co-solvents, such as polymers, the exclusion is primarily driven by excluded volume interactions. However, the exclusion of co-solvents, such as electrolytes, can be caused by other mechanisms. In this review, we summarize the literature on interparticle depletion forces that arise from repulsive image-charge forces between low-dielectric particles and electrolytes. In particular, we emphasize the results from a variational perturbation theory for describing the salting-out behavior observed in moderately concentrated salt solutions. The theory predicts an unscreened force with a range given by the Bjerrum length and a magnitude proportional to the osmotic pressure of the salt solution. The force becomes significant at the same salt concentration where salting-out behavior is typically observed.

ORCID iDs

Curtis, Robin A. and Lue, Leo ORCID logoORCID: https://orcid.org/0000-0002-4826-5337;
CORE (COnnecting REpositories)