A micropore nanoband electrode array for enhanced electrochemical generation/analysis in flow systems

Abstract

Our previous work has established that micron-resolution photolithography can be employed to make microsquare nanoband edge electrode (MNEE) arrays. The MNEE configuration enables systematic control of the parameters (electrode number, cavity array spacing, and nanoelectrode dimensions and placement) that control geometry, conferring a consistent high-fidelity electrode response across the array (e.g., high signal, high signal-to-noise, low limits of detection and fast, steady-state, reproducible and quantitative response) and allowing the tuning of individual and combined electrode interactions. Building on this, in this paper we now produce and characterise a micropore nanoband electrode (MNE) array designed for flow-through detection, where an MNEE edge electrode configuration is used to form a nanotube electrode embedded in the wall of each micropore, formed as an array of pores of controlled size and placement through an insulating membrane of sub-micrometer thickness. The success of this approach is established by the close correspondence between experiment and simulation and the enhanced and quantitative detection of redox species flowing through the micropores over the very wide range of flow rates relevant, e.g., to applications in (bio)sensing and chromatography. Quantitative electrochemical reaction with low conversion, suitable for analysis, is demonstrated at high flow, whilst quantitative electrochemical reaction with high conversion, suitable for electrochemical product generation, is enabled at lower flow. The fundamental array response is analysed in terms of established flow theories, demonstrating the additive contributions of within-pore enhanced diffusional (nanoband edge) and advective (Levich-type) currents, the control of the degree of diffusional overlap between pores through pore spacing and flow rate, the control by design across length scales ranging from nanometer through micrometer to a centimetre array, and the ready determination of physicochemical parameters, enabling discussion of the potential of this breakthrough technology to address unmet needs in generation and analysis.