Understanding Nano-Impacts: Binary Nature of Charge Transfer during Mediated Reactions

We report mediated charge transfer across a nanoparticle that Faradaically interacts with its surrounding solution while impacting on an electrochemically inactive electrode. To this end, two different aspects of the process are elucidated and interconnected: The Faradaic reaction at the particle surface and electron tunnelling between the electrode and the particle. Results demonstrate that the charge transfer can be described through a binary model, in which the current switches between the limiting Faradaic current and no current at all as a function of the electrode-particle distance, while the response is largely unrelated to the analyte's formal potential. This finding allows a significantly simplified modelling approach in future studies.