Characterization of Nanopore Electrode Structures as Basis for Amplified Electrochemical Assays

A nanopore electrode structure was fabricated consisting of ensembles of nanopores with separately addressable electrodes at the pore bottoms and the rims. A metal/insulator/metal layer structure allowed for adjusting the spacing between the bottom and rim electrodes to be in the range of about 200 nm. Pore diameters varied between 200 and 800 nm. The electrochemical properties of this electrode structure and its perspectives for applications in bioelectronics were studied using cyclic voltammetry and chronoamperometry along with high-resolution scanning electrochemical microscopy (SECM) in constant-distance mode. It was possible to visualize the electrochemical activity of a single nanometric electrode using high-resolution SECM in a combination of sample-generation-tip-collection mode and positive feedback mode. The SECM images suggested an influence of the unbiased rim electrode on redox amplification which was used as a basis for evaluating the feasibility of current amplification by means of redox cycling between the bottom and rim electrodes. Amplification factors superior to those obtained with interdigitated array electrodes could be demonstrated.