Contact-Tolerant Nano/Sub-Micrometer Disk Electrodes with Small RG and High Mechanical Compliance

Abstract Disk-shaped ultramicroelectrodes with well-defined geometry and small RG values are widely used as scanning electrochemical microscopy (SECM) probes; however, conventional glass-sealed architectures are mechanically fragile and prone to damage under contact or near-contact operating conditions, limiting their practical use under contact-prone or mechanically challenging measurement conditions. Herein, a straightforward Bi template-assisted strategy is reported for fabricating contact-tolerant Au nano/sub-micrometer disk electrodes (Au NEs) with a high-aspect-ratio tapered structure. The resulting electrodes exhibit an experimentally demonstrated RG range of approximately 1.2−2.5 and mechanically compliant tapered supports. The active tip dimensions are corroborated by the agreement between SEM-observed dimensions and electroactive radii derived from steady-state currents. In addition, the fabricated probes enable reliable quantitative SECM operation at short tip-to-substrate distances, as verified by the agreement between experimental and theoretical approach curves. Repetitive bending-recovery tests further demonstrate stable electrochemical responses after repeated contact events, with the probe tolerating approximately 885 μm of continued axial displacement after contact before fracture. Thus, by integrating structural flexibility with a small RG, this method provides a practical route to robust Au nano/sub-micrometer disk probes for SECM under contact-prone conditions.