Testing one component plasma models on colloidal overcharging phenomena

Abstract

In this paper, the mechanisms of overcharging of a colloidal macroion in the presence of multivalent counterions are investigated by means of Monte Carlo simulations. This computational technique appears as a powerful tool for probing the validity of semianalytical models developed for this issue. In particular, the simulations performed are compared with the predictions of two different models based on the one component plasma (OCP) theory. Therein, the multivalent ionic atmosphere confined at the macroion surface is approximated by a two-dimensional Wigner crystal. These kinds of models are largely used in the literature since (in some cases) they present quite simple equations to describe the electric double layer (EDL) of macroions with different geometries in the presence of much smaller (but still multivalent) ions. In this sense, charge inversion phenomena of membranes, polyelectrolytes, DNA molecules, etc., are straightforwardly predicted in terms of these expressions. Unfortunately, comparisons between these predictions and experimental results are scarce, mostly due to the difficulty to reproduce the experimental conditions in the laboratory. Accordingly, the goal of the present paper is to simulate EDLs under real conditions (in which overcharging phenomena are expected to happen) and use the results obtained in this way for comparing with those obtained from OCP models.

Effect of the surface charge discretization on electric double layers: A Monte Carlo simulation study

“…In fact, multivalent counterions can form two-dimensional crystals even in the absence of surface charge discretization as a result of strong electrostatic correlations. 45,46 For z =2a, the slight depression previously reported for DISC2 and monovalent salts ͓see Fig. 10͑b͔͒ has, however, disappeared for 2:1 electrolytes.…”

Simulation of charge reversal in salty environments: Giant overcharging?

“…On the other hand, the more recent theory of Pianegonda et al [15] contains the necessary ingredients for a good description, even though the quantitative agreement with simulations is still not satisfactory [25].…”

“…Tanaka and Grosberg have performed simulations of the electrophoresis of a colloid in salt solution in a regime of very high surface charge [20]. Martin-Molina et al [24,25] simulate the overcharging at a planar wall in salty environment under more realistic conditions, which should be valid in the limit of large colloids. Diehl and Levin [26] have performed Monte Carlo simulations of a spherical colloid, where the ζ-potential is measured.…”

Recent developments in electrokinetics of salt-free concentrated suspensions

“…Monte Carlo simulations or predicted by microscopic theories that accounts for such correlations [75,76].…”