Electrochemical Detection of Gold Nanoparticle Collisions Using Nanopore Electrode Array (NEA) Devices

The ability to perform single entity experiments on complex nanostructures is of significant research interest, as complete characterizations of individual nanoparticles can provide valuable insight that cannot be provided by ensemble measurements. However, the isolation of single entities can be difficult with current methods, such as ultramicroelectrodes (UMEs) or nanopipettes that to not truly guarantee isolation of a single nanoparticle. Nanopore electrode arrays (NEAs) previously developed by Bohn and coworkers allow for single nanoparticle electrochemical collision experiments with 40 nm diameter silver nanoparticles (AgNP). The goal of this research was to fabricate these previously developed NEAs using previously established techniques, and then to electrochemically detect oxidation events from collisions with a single, extremely small (< 5 nm diameter) gold nanoparticle (AuNP) as a model for more complex nanostructures, such as gold monolayer protected clusters (Au-MPCs), and more complex processes, such as single entity electrocatalysis. The NEA devices were cleaned with both organic solutions and electrochemically via cyclic potential sweeps, and then chronoamperometry experiments were performed. A patch clamp amplifier and digitizer system was chosen to apply potential and detect faradaic current, and it was found that high noise levels and capacitive current make detection of ultrasmall nanostructures significantly difficult, however, through significant statistical testing and diligence in noise reduction, capacitive current compensation, and background measurements, an oxidation event can be detected and confirmed for these small structures under ideal conditions.