Dense Array of Nanoparticles as a Large-Area Nanoelectrode for Sensors: An Oxymoron Mesomaterial?

Compared to redox reactions at large electrodes, those at nanoscale electrodes are controlled by kinetics rather than diffusion, thus resulting in responses that are orders of magnitude faster at higher sensitivity. To avoid interference by diffusion-flux domains of adjacent particles, for monolayers of nanoparticles as individual electrodes, the area coverage should be below approximately 10%, which is well below the percolation threshold of 45%. Conducting monolayer arrays consisting of a network of one-dimensional necklaces of 10nm Au particles with 54 to 26% area coverage are shown to behave like ultramicroelectrodes and nanoelectrode ensembles (NEEs). The reconciliation of the two opposing requirements of high and low coverage for percolation and NEE behavior, respectively, is attributed to the necklace-network topology.