Rectification of bipolar nanopores in multivalent electrolytes: effect of charge inversion and strong ionic correlations
arXiv:2011.07404 · doi:10.1039/D0CP03237A
Abstract
Bipolar nanopores have powerful rectification properties due to the asymmetry in the charge pattern on the wall of the nanopore. In particular, bipolar nanopores have positive and negative surface charges along the pore axis. Rectification is strong if the radius of the nanopore is small compared to the screening length of the electrolyte so that both cations and anions have depletion zones in the respective regions. The depths of these depletion zones is sensitive to sign of the external voltage. In this work, we are interested in the effect of the presence of strong ionic correlations (both between ions and between ions and surface charge) due to the presence of multivalent ions and large surface charges. We show that strong ionic correlations cause leakage of the coions, a phenomenon that is absent in mean field theories. In this modeling study, we use both the mean-field Poisson-Nernst-Planck (PNP) theory and a particle simulation method, Local Equilibrium Monte Carlo (LEMC), to show that phenomena such as overcharging and charge inversion cannot be reproduced with PNP, while LEMC is able to produce nonmonotonic dependence of currents and rectification as a function of surface charge strength.
References in corpus (6)
- Poisson Nernst-Planck Model of Ion Current Rectification through a Nanofluidic Diode
- Charge neutrality breakdown in confined aqueous electrolytes: theory and simulation
- Multiscale analysis of the effect of surface charge pattern on a nanopore's rectification and selectivity properties: from all-atom model to Poisson-Nernst-Planck
- Simulation of a model nanopore sensor: ion competition underlies device behavior
- Application of a bipolar nanopore as a sensor: rectification as an additional device function
- Energetics of ion competition in the DEKA selectivity filter of neuronal sodium channels