Fabrication of carbon microelectrodes with an effective radius of 1 nm

A method for producing insulated nanometer-sized carbon electrodes is presented. These electrodes are produced using electrochemical etching of carbon fibers followed by deposition of electrophoretic paint. A new deposition approach for insulating the tips, the so-called "inverted deposition" technique, is introduced. This technique allows complete insulation of the whole body of the etched carbon fiber except for the very tip, leaving an electrochemical active area with effective diameters as small as a few nanometers. The process overcomes pinhole formation that can be a problem with the normal electrophoretic paint deposition process. The fabricated electrodes show ideal steady-state voltammetric behavior. The voltammetric response corresponding to the reduction of hexacyanoferrate(III) and hexaammineruthenium(III) is investigated on these small electrodes in the absence and presence of supporting electrolyte. For these two multiple-charged ions the steady-state voltammetric behavior in the absence of supporting electrolyte is found to deviate from expected behavior, especially at very small electrodes. (C) 2002 Elsevier Science B.V. All rights reserved.