Counterions at charge-modulated substrates

TL;DR

This paper investigates how counterions behave near charged surfaces with spatially varying charge distributions, revealing significant deviations from uniform charge models especially under strong coupling conditions.

Contribution

It introduces a combined Monte-Carlo and strong-coupling theoretical approach to analyze counterion distributions on charge-modulated substrates, highlighting the importance of lateral correlations.

Findings

Counterions show strong lateral correlations with surface charges.

Density profiles are significantly altered by charge modulation.

High surface charge and multivalent counterions amplify deviations from uniform models.

Abstract

We consider counterions in the presence of a single planar surface with a spatially inhomogeneous charge distribution using Monte-Carlo simulations and strong-coupling theory. For high surface charges, multivalent counterions, or pronounced substrate charge modulation the counterions are laterally correlated with the surface charges and their density profile deviates strongly from the limit of a smeared-out substrate charge distribution, in particular exhibiting a much increased laterally averaged density at the surface.