Characterization of the diffusion limited current at ultra-small carbon ring electrodes

Ultra-small ring-shaped carbon electrodes of micrometer dimension are characterized. The carbon films deposited by the pyrolysis of methane inside fused silica microstructures are fibrous and appear porous. However, voltammetry at these electrodes is not affected dramatically by the porous nature of the carbon since sealing epoxy acts as a filler. Determination of the electrode dimensions and surface morphology is accomplished with scanning electron microscopy. The theoretical limiting current at shielded electrodes is better approximated by data at cleaved rather than polished electrodes. Prolonged polishing appears to cover the thin ring structure with epoxy or other non-conducting material and can lead to a total inhibition of the electron transfer process.