Simulation-based investigations on noise characteristics of redox-cycling sensors

We describe a simulation framework for the modeling of electrochemical processes within nanocavity redox-cycling devices. Nanocavity devices feature two closely spaced and individually biased electrodes that are incorporated into a nanofluidic channel. This setup enables the repeated participation of certain molecules in subsequent redox reactions at the two electrodes, hence leading to a strong amplification of the electrochemical signal. Our simulation is based on stochastic random walks that represent single molecule trajectories; electrochemical reactions are modeled on the molecular level. The presented approach reveals insight into the dependency of the sensor's current noise characteristics on geometrical features. We describe the simulation of two key geometries and identify two distinct types of noise that can be discriminated by their characteristics in the frequency domain. Schematic of a random-walk approach for the simulation of the redox-cycling effect. A single molecule trajectory is indicated, differently colored spheres specify the molecule occupying different oxidation states throughout its pathway.