Nanometer-sized glass-sealed metal ultramicroelectrodes (UMEs) have be
en 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 ou
t by a combination of steady-state voltammetry, scanning electron micr
oscopy (SEM), and scanning electrochemical microscopy (SECM). The cycl
ic voltammograms obtained have a regular shape with very small capacit
ive and resistive background. The effective electrode radii obtained f
rom voltammetry were between 2 and 500 mn. From the SEM micrographs, t
he shape of polished tips appears to be close to a microdisk, while th
e geometry of etched electrodes is closer to conical. Accordingly, the
SECM current-distance curves (i(T)-d) obtained with polished electrod
es fit well the theory for a disk-shaped tip, while a 20-nm-radius etc
hed electrode was shown to be a fairly sharp cone with a height-to-rad
ius ratio of about 2.5. The experimental data were compared to the the
ory developed for disk-shaped, conical, and recessed tips to demonstra
te suitability of the produced electrodes for quantitative electrochem
ical experiments. The prospects of steady-state measurements of the ra
tes of fast heterogeneous reactions are discussed. Submicrometer-sized
ion selective electrodes (ISEs) were prepared by coating etched Ag ti
ps with silver iodide. The concentration response of such ISEs remaine
d stable and linear after coating of the ISEs with protective Nafion f
ilm.