Nanometer-Sized Electrochemical Sensors
1997
Nanometer-sized glass-sealed metal ultramicroelectrodes (UMEs) have been prepared using a laser-based micropipet puller. The tip was exposed to solution either by etching away a small portion of glass insulator or by micropolishing. The characterization of the UMEs was carried out by a combination of steady-state voltammetry, scanning electron microscopy (SEM), and scanning electrochemical microscopy (SECM). The cyclic voltammograms obtained have a regular shape with very small capacitive and resistive background. The effective electrode radii obtained from voltammetry were between 2 and 500 nm. From the SEM micrographs, the shape of polished tips appears to be close to a microdisk, while the geometry of etched electrodes is closer to conical. Accordingly, the SECM current−distance curves (iT−d) obtained with polished electrodes fit well the theory for a disk-shaped tip, while a 20-nm-radius etched electrode was shown to be a fairly sharp cone with a height-to-radius ratio of about 2.5. The experimental d...
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