Size effect in ion transport through angstrom-scale slits

TL;DR

This study demonstrates ion transport through atomically precise angstrom-scale slits, revealing size-dependent permeation and asymmetry between ions, advancing understanding of nanofluidic confinement effects.

Contribution

It introduces a method to fabricate and study atomically flat angstrom-scale slits, providing new insights into ion transport at the atomic scale.

Findings

Larger hydrated ions can permeate narrow slits with reduced mobility.

Ion transport shows asymmetry between anions and cations.

Slit fabrication enables detailed study of nanoscale confinement effects.

Abstract

It has been an ultimate but seemingly distant goal of nanofluidics to controllably fabricate capillaries with dimensions approaching the size of small ions and water molecules. We report ion transport through ultimately narrow slits that are fabricated by effectively removing a single atomic plane from a bulk crystal. The atomically flat angstrom-scale slits exhibit little surface charge, allowing elucidation of the role of steric effects. We find that ions with hydrated diameters larger than the slit size can still permeate through, albeit with reduced mobility. The confinement also leads to a notable asymmetry between anions and cations of the same diameter. Our results provide a platform for studying effects of angstrom-scale confinement, which is important for development of nanofluidics, molecular separation and other nanoscale technologies.