Attoampere Nanoelectrochemistry

TL;DR

This paper demonstrates the ability to perform electrochemical measurements at the attoampere level with high spatial resolution, enabling single-molecule sensitivity and detailed molecular insights.

Contribution

It introduces a GHz microscope technique that achieves sub aA current detection at nanoscale, surpassing previous measurement limits and allowing single-molecule electrochemical analysis.

Findings

Achieved electrochemical measurements at <80 nm resolution and sub aA currents.

Revealed two molecular configurations with similar redox potentials.

Provided atomistic insights into electron transfer reactions.

Abstract

Local electrochemical measurements and imaging at the nanoscale are crucial for the future development of molecular devices, sensors, materials engineering, electrophysiology and various energy applications from artificial photosynthesis to batteries. The ultimate step towards single-molecule sensitivity requires the measurement of aA currents, which is three orders of magnitude below that of current state-of-the-art measurement abilities. Here, we show electrochemical measurements at the sub aA level and <80 nm spatial resolution, that we reach by exploiting the ultra-high sensitivity of our GHz microscope for local faradaic interface capacitances. We demonstrate this for a well-known surface-bound ferrocene alkyl monolayer, a system that cannot be studied at the nanoscale unless large nanoarrays are used11. We report the simultaneous measurement of local cyclic voltammograms (CV) which provide atomistic information on the respective electron transfer reaction and reveal two molecular configurations with a similar redox energy potential -- insights inaccessible by electrochemical ensemble measurements.