Electrostatics of Colloidal Particles Confined in Nanochannels: Role of Double-Layer Interactions and Ion-Ion Correlations

TL;DR

This study uses computational methods to explore how ion interactions influence the behavior of charged colloids in nanochannels, revealing conditions where like-charged particles attract and identifying preferred colloid positions.

Contribution

It provides new insights into ion-mediated colloid interactions in nanochannels, highlighting the effects of multivalent ions and ion correlations using multiple simulation and theoretical approaches.

Findings

Like-charged colloids can attract in certain multivalent ion regimes.

Preferred colloid positions include the channel center and near the walls.

Energy barriers and minima influence colloid stability and placement.

Abstract

We perform computational investigations of electrolyte-mediated interactions of charged colloidal particles confined within nanochannels. We investigate the role of discrete ion effects, valence, and electrolyte strength on colloid-wall interactions. We find for some of the multivalent charge regimes that the like-charged colloids and walls can have attractive interactions. We study in detail these interactions and the free energy profile for the colloid-wall separation. We find there are energy barriers and energy minima giving preferred colloid locations in the channel near the center and at a distance near to but separated from the channel walls. We characterize contributions from surface overcharging, condensed layers, and overlap of ion double-layers. We perform our investigations using Coarse-Grained Brownian Dynamics simulations (BD), classical Density Functional Theory (cDFT), and mean-field Poisson-Boltzmann Theory (PB). We discuss the implications of our results for phenomena in nanoscale devices.