Charge-regulation effects in nanoparticle self-assembly

TL;DR

This paper introduces a hybrid simulation method to model charge regulation in nanoparticles, revealing its significant impact on self-assembly structures and clarifying when constant-charge models are sufficient.

Contribution

A novel hybrid Monte Carlo/Molecular Dynamics approach that dynamically models charge regulation effects in nanoparticle self-assembly.

Findings

Charge regulation qualitatively alters self-assembled structures.

Charge redistribution stabilizes asymmetric nanoparticle constructs.

Conditions where constant-charge approximation is valid are identified.

Abstract

Nanoparticles in solution acquire charge through dissociation or association of surface groups. Thus, a proper description of their electrostatic interactions requires the use of charge-regulating boundary conditions rather than the commonly employed constant-charge approximation. We implement a hybrid Monte Carlo/Molecular Dynamics scheme that dynamically adjusts the charges of individual surface groups of objects while evolving their trajectories. Charge-regulation effects are shown to qualitatively change self-assembled structures due to global charge redistribution, stabilizing asymmetric constructs. We delineate under which conditions the conventional constant-charge approximation may be employed and clarify the interplay between charge regulation and dielectric polarization.