Electrochemical response of biased nanoelectrodes in solution

TL;DR

This paper investigates the electrochemical behavior of biased nanoelectrodes in ionic solutions, revealing slow transient responses and noise characteristics crucial for DNA sequencing technologies, supported by experimental and theoretical analysis.

Contribution

It introduces a non-equilibrium stochastic model explaining the slow ionic current decay and noise increase in nanoelectrodes, aligning with experimental data.

Findings

Large background currents with slow decay observed

Transient response decays over time due to diffusion layer formation

Model accurately predicts experimental ionic current behavior

Abstract

Novel approaches to DNA sequencing and detection require the measurement of electrical currents between metal probes immersed in ionic solution. Here, we experimentally demonstrate that these systems maintain large background currents with a transient response that decays very slowly in time and noise that increases with ionic concentration. Using a non-equilibrium stochastic model, we obtain an analytical expression for the ionic current that shows these results are due to a fast electrochemical reaction at the electrode surface followed by the slow formation of a diffusion layer. During the latter, ions translocate in the weak electric field generated after the initial rapid screening of the strong fields near the electrode surfaces. Our theoretical results are in very good agreement with experimental findings.