Preparation and characterization of carbon powder paste ultramicroelectrodes as tips for scanning electrochemical microscopy applications.

We report a simple method of preparation of carbon paste ultramicroelectrodes (UMEs) for use as probe tips in scanning electrochemical microscopy (SECM). Carbon paste UMEs were prepared by packing the carbon paste into a chemically etched tip of a Pt-UME or a pulled glass capillary. Carbon-based UMEs are attractive in micrometer to nanometer gap experiments and in electrodeposition of single metal nanoparticles for electrocatalytic studies because of their high overpotential in proton and oxygen reduction. We have demonstrated the preparation of conically shaped carbon paste UMEs, appropriate for SECM measurements and micrometer to nanometer gap experiments.