Fabrication and characterization of self-assembled spherical gold ultramicroelectrodes

Spherical ultramicroelectrodes with diameters of 1-30 μm have been prepared by self-assembly of Au nanoparticles and 1,9-nonanedithiol molecules at the tip end of glass micropipets. The electrodes were characterized by optical and scanning electron microscopy, cyclic voltammetry in aqueous and acetonitrile solution, and scanning electrochemical microscopy approach curves. A modified theory for hemispherical electrodes was used to compute the approach curves, which agreed with the experimental results. The construction strategy represents a bottom-up approach to the fabrication of microspherical electrodes.