Ion-ion correlation and charge reversal at titrating solid interfaces

TL;DR

This paper demonstrates through simulations and experiments that ion-ion correlations are crucial for understanding surface charge behavior and charge reversal at titrating solid interfaces, especially with divalent ions.

Contribution

It provides the first clear evidence that ion-ion correlations cause charge reversal and highly charged surfaces, aligning simulations with experimental results without fitting parameters.

Findings

Ion-ion correlations explain charge reversal phenomena.

Simulations and experiments show excellent agreement.

Charge correlations lead to anomalous charge regulation.

Abstract

Confronting grand canonical titration Monte Carlo simulations (MC) with recently published titration and charge reversal (CR) experiments on silica surfaces by Dove et al. and van der Heyden it et al, we show that ion-ion correlations quantitatively explain why divalent counterions strongly promote surface charge which, in turn, eventually causes a charge reversal (CR). Titration and CR results from simulations and experiments are in excellent agreement without any fitting parameters. This is the first unambiguous evidence that ion-ion correlations are instrumental in the creation of highly charged surfaces and responsible for their CR. Finally, we show that charge correlations result in "anomalous" charge regulation in strongly coupled conditions in qualitative desagreement with its classical treatment.