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Issue 24, 2014
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Specific ion effects induced by mono-valent salts in like charged aggregates in water

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Abstract

While salt mediated association between similarly charged poly-electrolytes occurs in a broad range of biological and colloidal systems, the effects of mono-valent salts remains little known experimentally. In this communication we systematically study influences of assorted mono-valent salts on structures of and interactions in two dimensional ordered bundles of charged fibrils assembled in water using Small Angle X-ray Scattering (SAXS). By quantitatively analyzing the scattering peak features, we discern two competing effects with opposite influences due to partitioning of salts in the aqueous complex. While electrostatic effects from salts residing between the fibrils suppress attraction between fibrils and expand the bundles, it is compensated by external osmotic pressure from peripheral salts in the aqueous media. The balance between the two effects varies for different salts and gives rise to ion-specific equilibrium behavior as well as structure of ordered bundles in salty water. The specific ions effects in like charged aggregates can be attributed to preferential distribution of ions inside or outside the bundles, correlated to the ranking of ions in Hofmeister series for macromolecules. Unlike conventional studies on Hofmeister effects by thermodynamic measurements relying on modeling for data interpretation, our study is based directly on structural analysis and is model-insensitive.

Graphical abstract: Specific ion effects induced by mono-valent salts in like charged aggregates in water

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Publication details

The article was received on 20 Nov 2013, accepted on 12 Mar 2014 and first published on 14 Mar 2014


Article type: Communication
DOI: 10.1039/C3SM52925H
Citation: Soft Matter, 2014,10, 4236-4240
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    Specific ion effects induced by mono-valent salts in like charged aggregates in water

    N. Huang, J. Tao, J. Liu, S. Wei, L. Li and Z. Wu, Soft Matter, 2014, 10, 4236
    DOI: 10.1039/C3SM52925H

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