Scaling behavior for ionic transport and its fluctuations in individual carbon nanotubes

TL;DR

This study investigates ionic transport and current fluctuations in individual carbon nanotubes, revealing a power law conductance behavior at low salinity and linking noise amplitude to surface charge, advancing understanding of nanoscale ionic conduction.

Contribution

It introduces a model explaining conductance scaling via hydroxide adsorption and surface charge effects, contrasting with boron nitride nanotubes.

Findings

Conductance follows a power law with salt concentration, exponent ~1/3.

Noise amplitude scales with surface charge and collapses onto a master curve.

Surface charge influences ionic current fluctuations in CNTs.

Abstract

In this letter we perform an experimental study of ionic transport and current fluctuations inside individual Carbon Nanotubes (CNT). The conductance exhibits a power law behavior at low salinity, with an exponent close to 1/3 versus the salt concentration. This scaling behavior is rationalized in terms of a model accounting for hydroxide adsorption at the (hydrophobic) carbon surface, leading to a density dependent surface charge. This is in contrast to boron nitride nanotubes which exhibit a constant surface conductance. Further we measure the low frequency noise of the ionic current in CNT and show that the amplitude of the noise scales with the surface charge, with data collapsing on a master curve for the various studied CNT at a given pH.