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Ion specificity and anomalous electrokinetic effects in hydrophobic nanochannels

David M. Huang·Cecile Cottin-Bizonne·Christophe Ybert·Lyderic Bocquet
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Abstract

We demonstrate with computer simulations that anomalous electrokinetic effects, such as ion specificity and non-zero zeta potentials for uncharged surfaces, are generic features of electro-osmotic flow in hydrophobic channels. This behavior is due to the stronger attraction of larger ions to the ``vapour--liquid-like'' interface induced by a hydrophobic surface. An analytical model involving a modified Poisson--Boltzmann description for the ion density distributions is proposed, which allows the anomalous flow profiles to be predicted quantitatively. This description incorporates as a crucial component an ion-size-dependent hydrophobic solvation energy. These results provide an effective framework for predicting specific ion effects, with important implications for the modeling of biological problems.

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David M. Huang, Cecile Cottin-Bizonne, Christophe Ybert, Lyderic Bocquet. 2007-01-04. Ion specificity and anomalous electrokinetic effects in hydrophobic nanochannels. https://doi.org/10.1103/physrevlett.98.177801

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