Ion-Specific Anomalous Electrokinetic Effects in Hydrophobic Nanochannels

David Huang , Cécile Cottin-Bizonne (1) , Christophe Ybert (1) , Lydéric Bocquet (1)

1 LPMCN - Laboratoire de Physique de la Matière Condensée et Nanostructures

We show with computer simulations that anomalous electrokinetic effects, such as ion specificity and nonzero zeta potentials for uncharged surfaces, are generic features of electro-osmotic flow in hydro-phobic channels. This behavior is due to the stronger attraction of larger ions to the ''vapor-liquidlike'' interface induced by a hydrophobic surface. We propose an analytical model involving a modified Poisson-Boltzmann description for the ion density distributions that quantitatively predicts the anomalous flow profiles. This description includes as a crucial component an ion-size-dependent hydrophobic solvation energy. These results provide an effective framework for predicting ion-specific effects, with potentially important implications for biological modeling.

Domaines: Matière Condensée [cond-mat]

David Huang, Cécile Cottin-Bizonne, Christophe Ybert, Lydéric Bocquet. Ion-Specific Anomalous Electrokinetic Effects in Hydrophobic Nanochannels. Physical Review Letters, 2007, 98 (17), ⟨10.1103/PhysRevLett.98.177801⟩. ⟨hal-01628759⟩