Charge Inversion of Divalent Ionic Solutions in Silica Channels

TL;DR

This study uses all-atomic molecular dynamics simulations to explain charge inversion phenomena observed in silica nanochannels with divalent ions, aligning well with experimental results and advancing understanding of ionic correlations at interfaces.

Contribution

The paper provides a detailed molecular dynamics explanation for charge inversion in silica channels, bridging experimental observations and theoretical understanding.

Findings

Charge inversion occurs due to ionic correlations at the silica-water interface.

Simulations match experimental streaming current measurements.

Insights into ionic interactions influence nanofluidic device design.

Abstract

Recent experiments (F.H.J. Van Der Heyden et al., PRL 96, 224502 (2006)) of streaming currents in silica nanochannels with divalent ions report charge inversion, i.e. interfacial charges attracting counterions in excess of their own nominal charge, in conflict with existing theoretical and simulation results. We reveal the mechanism of charge inversion by using all-atomic molecular dynamics simulations. Our results show excellent agreement with experiments, both qualitatively and quantitatively. We further discuss the implications of our study for the general problem of ionic correlations in solutions as well as in regards of the properties of silica-water interfaces.