Current rectification by nanoparticles in bipolar nanopores

TL;DR

This study demonstrates that adding charged nanoparticles to bipolar nanopores significantly enhances current rectification, with potential applications in energy storage, by leveraging the electric fields generated by the nanoparticles within the channels.

Contribution

It introduces a molecular-level model showing how charged nanoparticles increase rectification in bipolar nanopores, highlighting the influence of geometry and charge distribution.

Findings

Charged nanoparticles can increase rectification by about tenfold.

The effect depends on pore geometry and nanoparticle charge sign.

Electric fields from nanoparticles are key to enhanced rectification.

Abstract

Bipolar nanochannels comprising two domains of positively and negatively charged walls along the pore axis are known to rectify current when exposed to an electric potential bias. We find that addition of charged nanoparticles can increase rectification considerably, by approximately one order of magnitude. Two bipolar channel geometries are considered here; their behavior is examined at rest and under the influence of a negative bias and a positive bias, respectively. We do so by relying on a molecular-level model of the electrolyte solution in the channels. The large increase in current rectification can be explained by the inherent electric field that charged nanoparticles generate within the channel. This effect is found to be largely dependent on the pore's geometry, its charge distribution, and the sign of the nanoparticles' charge, thereby offering new opportunities for design of engineered nanopore membrane-nanoparticle systems for energy storage.