Voltammetric sizing and shaping of a cylinder

A reversible electron transfer is studied at a microdisk electrode which is partially blocked by an inert particle at the disk center. The inert particle is either a cylinder of a sphere. The size of a cylinder located at the center of the microdisk electrode is determined with the help of a simple electrochemical procedure. Cyclic voltammograms for the reduction of a reversible redox system are recorded as a function of scan rate and compared to simulations. Excellent agreement between theory and experiment was found. Modelling diffusion to a microdisk electrode modified with a sphere or cylinder at its center by numerical simulations gives physical support for the transition in diffusion-layer shape and size, therefore allowing to size not only particles of known shape but also, in principle, to determine their shape and size simultaneously.