We developed a high-resolution scanning electrochemical microscope (SECM) for the characterization of variousbiological materials. Electrode probes were fabricated by Ti/Pt sputtering followed by parylene C-vapor depositionpolymerization on the pulled optical fiber or glass capillary. The effective electrode radius estimated from the cyclicvoltammogram of ferrocyanide was found to be 35 nm. The optical aperture size was less than 170 nm, which wasconfirmed from the cross section of the near-field scanning optical microscope (NSOM) image of the quantum dot(QD) particles with diameters in the range of 10-15 nm. The feedback mechanism controlling the probe-sampledistance was improved by vertically moving the probe by 0.1-3
m to reduce the damage to the samples. This feedbackmode, defined as "standing approach (STA) mode" (
Yamada, H.; Fukumoto, H.; Yokoyama, T.; Koike, T.
Anal. Chem.2005,
77, 1785-1790), has allowed the simultaneous electrochemical and topographic imaging of the axons and cellbody of a single PC12 cell under physiological conditions for the first time. STA-mode feedback imaging functionsbetter than tip-sample regulation by the conventionally available AFM. For example, polystyrene beads (diameter~6
m) was imaged using the STA-mode SECM, whereas imaging was not possible using a conventional AFMinstrument.