Snapshot Redox Cycling Voltammetry (Snapshot RCV): Fast Generation-Collection Detection across a Wide Potential Range at a Chip-Based Microelectrode Array

Abstract

During generation-collection, redox-active species oxidize (or reduce) at generator electrodes and electrochemically convert back at neighboring collector electrodes, yielding dual-current signals shaped by mass transport, reaction kinetics, and scaled by analyte concentration. As electrode spacing decreases, diffusion layers overlap, recycling species in a feedback loop (redox cycling, RC) and amplifying observed currents. While advantageous, conventional RC techniques experience challenges: chronoamperometry (CA) offers high temporal resolution but lacks thermodynamic insight, while cyclic voltammetry (CV) captures the potential window but is constrained by scan duration and background current at high speeds. Here, snapshot redox cycling voltammetry (Snapshot RCV) is introduced, which constructs the profile of a conventional RC voltammogram without a potential sweep. By simultaneously biasing individual generator electrodes in a microband array to different voltages across the potential range while individually holding collector electrodes at a reversing potential, high-resolution “spatial” voltammograms are obtained in as little as 1 s, providing steady-state generation-collection profiles on a chronoamperometric time scale. This method was evaluated using 0.50 mM Ru(NH₃)₆Cl₃ in 0.10 M KCl on a seven-electrode gold microband array (width = 4.08 μm, gap = 4.14 μm, length = 97.17 μm). Snapshot RCV was then performed on other analytes (dopamine (DA), 3,4-dihydroxyphenylalanine (L-DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), and ascorbic acid (AA)) with different electrochemical properties: standard reduction potentials (E°), electron transfer rate constants (k°), and following chemical reaction rates. Snapshot RCV captures the voltammetric shape with a 10%–60% increase in collection efficiency over Conventional RCV and can isolate inner array electrochemistry from edge contributions, allowing for postexperimental geometric filtering. The different collection efficiencies and voltammetric shapes from redox-active molecules, driven by their thermodynamics, kinetics, and chemical mechanisms (EC, ECC′), could make Snapshot RCV a promising technique for qualitative and quantitative analysis while enabling rapid sensing that is also adaptable to confined spaces.