Electric Field Driven Surface Ion Transport in Hydrophobic Nanopores†

Abstract

Main observation and conclusionWater behavior in nanoconfined hydrophobic environment is different from that in the bulk, which greatly influences mass transport. Hydrophobicity switching of nanopores showing great potential for controlled water or ion transport has been realized through several methods, especially the voltage‐triggered wetting/dewetting inspired by biological ion channels. However, in the hydrophobic silanized nanopores, the finite ionic current is still observed and the ion transport mechanism is not yet clear. Here, we explore the ion transport behavior in the hydrophobic silanized anodic aluminum oxide (AAO). Ion transport through this hydrophobic membrane is confirmed, although no aqueous pathway was observed. Results show that ions transport through the cross‐linked silane layer on the inner surface. It is revealed that metal ions, not just the protons or hydroxide ions, are involved in the ion transport driven by external electric field. This study provides a new insight into the ion transport in nanoconfined hydrophobic environment, which is helpful to understand the biological processes and design new nanofluidic devices.