Abstract
We have performed MD simulations of a highly charged colloid in a solution of 3:1 and additional 1:1 salt. The dependency of the colloid's inverted charge on the concentration of the additional 1:1 salt has been studied. Most theories predict, that the inverted charge increases when the concentration of monovalent salt grows, up to what is called giant overcharging, while experiments and simulational studies observe the opposite. Our simulations agree with the experimental findings and shed light onto the weaknesses of the theories.
Highlights
In this work we study the phenomenon of overcharging on the basis of the simple restrictive primitive model
The phenomenon has been demonstrated by electrophoresis experiments, where a reversed mobility has been observed for charged colloids in a solution that contained multivalent ions
This shows, that with growing salt concentration, more and more of these ions prefer to stay in the bulk. This can be interpreted in favour of the theory of Pianegonda et al [15], who take into account that the solvation energy of the multivalent ions in the bulk is larger when more salt is there. This effect reduces the reversed charge with growing salt concentration, which is the reason why the theory of Pianegonda et al is the only one-component plasma (OCP) theory that correctly describes a decrease in the effective charge at higher salt concentrations
Summary
In this work we study the phenomenon of overcharging on the basis of the simple restrictive primitive model. When a highly charged colloid (or macroion) is put into a solution that contains multivalent counterions, its charge can become overcompensated, such that the effective charge of the colloid-ion-complex becomes oppositely charged In the literature, this phenomenon is called charge reversal, charge inversion or overcharging. The phenomenon has been demonstrated by electrophoresis experiments, where a reversed mobility has been observed for charged colloids in a solution that contained multivalent ions (for a review, see [1]). Diehl and Levin [26] have performed Monte Carlo simulations of a spherical colloid, where the ζ-potential is measured This work complements these simulations by analyzing the case of a spherical colloid in salty environment in the experimental parameter regime, and comparing the results to the various assumptions made in the OCP theories
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
