Preparation and electrochemical response of 1-3 nm Pt disk electrodes

The preparation and characterization of Pt nanoelectrodes in the range of 1 to 3 nm in radii are reported. APt microwire is sealed into a bilayer quartz capillary and pulled into an ultrasharp Pt nanowire sealed in a silica tip using a laser-assisted pulling process. The ultrasharp tip is then sealed into a piece of glass tubing, which is manually polished to expose the Pt. Transmission electron microscopy and steady-state voltammetry are utilized to characterize the nanoelectrodes. The results show that the minimum size of the Pt nanoelectrode is determined by the size of the Pt microwire and parameters used in the pulling process. The heterogeneous electron transfer rate constant for the oxidation of ferrocene, ferrocenemethanol, and potassium hexachloroiridate (III) are determined from steady-state voltammetry using the method of Mirkin and Bard and are found to be [k.sup.o] = 7.6 [+ or -] 3.4 cm/s and = 0.85 [+ or -] 0.06 for ferrocene, [k.sup.o] = 7.4 [+ or -] 6.9 cm/s and = 0.78 [+ or -] 0.16 for ferrocenemethanol, and [k.sup.o] = 6.0 [+ or -] 4.2 cm/s and [alpha] = 0.72 [+ or -] 0.15 for Ir[[Cl.sub.6.sup.3-].