We report the electrochemical properties of carbon nanopipette, a new structural and morphological form of carbon nanostructures. The carbon nanopipettes are carbon whiskers with a base of 1-2 μm while tapering down to few nm over several tens of microns length with a hollow core of a constant diameter of about 2-20 nm. The outer shell is made up of helical sheets of graphite winding continuously around the hollow core. Nanopipettes are openended on both sides, mechanically rigid, and have a tip as sharp as a conventional nanotube, whereas the body of the nanopipette is robust. The mechanical rigidity and openness of both ends make these nanopipettes suitable for tissue and cell penetration applications toward localized drug delivery and sensing. Specifically, we prepared electrodes with arrays of nanopipettes exposed and tested their electrochemical response to dopamine in KCl solutions. The results demonstrate that dopamine redox reaction is nearly reversible in KCl solution (dEp < 100 mV). The response is stable over long periods of time after initial anodic treatment in acid. The electrochemical results are consistent with the expected kinetics based on the structural model for the carbon nanopipettes, I.e., the exterior surface and the tip are composed mainly with graphitic edge plane sites. The results suggest that the as-synthesized nanopipette arrays on polycrystalline diamond film covered platinum wires could directly be used for neurological solute detection in KCl environments.
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