Pink noise of ionic conductance through single artificial nanopores revisited

TL;DR

This study investigates pink noise in ionic conductance through single artificial nanopores, revealing that noise characteristics depend on the ionic liquid used and are linked to cooperative ion motion rather than pore geometry or wall charges.

Contribution

It provides new insights into the origin of pink noise in ionic transport, emphasizing the role of ionic liquids and cooperative ion dynamics in nanopores.

Findings

Pink noise amplitude is independent of concentration and pH in KCl solutions.

Ionic liquids significantly affect noise amplitude and conductivity.

Pink noise originates from cooperative ion motion, not pore geometry or wall charges.

Abstract

We report voltage-clamp measurements through single conical nanopore obtained by chemical etching of a single ion-track in polyimide film. Special attention is paid on the pink noise of the ionic current (i.e. $1/f$ noise) measured with different filling liquids. The relative pink noise amplitude is almost independent of concentration and pH for KCl solutions, but varies strongly using ionic liquids. In particular we show that depending on the ionic liquid, the transport of charge carriers is strongly facilitated (low noise and higher conductivity than in the bulk) or jammed. These results show that the origin of the pink noise can be ascribed neither to fluctuations of the pore geometry nor to the pore wall charges but rather to a cooperative effect on ions motion.