Recessed Gold Nanoring-Ring Microarray Electrodes.

A 6 × 6 recessed Au nanoring-ring electrodes microarray was fabricated over a glass substrate using focused ion beam milling. The electrochemical responses of this device to a reversible redox pair were examined. In redox-cycling mode, the lower ring acts as a generator and the upper ring as a collector. High collection efficiencies (close to 100%) and amplification factors (∼3.5) were achieved with this configuration. The redox-cycling behavior of this device was modeled using COMSOL Multiphysics. The effects of scaling the geometric parameters of the electrodes (ring height and radius), potential sweep rates, and inter-electrode gap distance were evaluated through simulations. The computational models showed that the attainable limiting current depends strongly on the ring radius, while it is almost independent of the ring height variations (for a particular inter-electrode gap). The effects of the scan rate and inter-electrode gap distance on the electrochemical characteristics of the device are also discussed. This study provides insights on the influence of the geometry on the performance of these arrays, which should guide the development of future applications.