On the Applicability of Conventional Voltammetric Theory to Nanoscale Electrochemical Interfaces

The voltammetric responses of Pt disk electrodes 5−50 nm in radii in the presence of excess inert electrolyte were investigated to verify the applicability of the conventional diffusion-based voltammetric theory to nanoscale electrochemical interfaces. A so-called “inverted heat-sealing” procedure was introduced in the electrode fabrication process to eliminate the possible tiny interstice between the glass sheath and electrode wire that could severely distort the voltammetric curves of nanometer-szied electrodes. Linear relations between the limiting currents (i L) and the concentrations of electroactive ions (c a) were found at electrodes as small as 5 nm, seemingly inferring that the classic voltammetric theory is applicable at such small electrodes. However, a delicate analysis on the dependences of i L on the electroactive size of electrode and the charge carried by the electroactive ions revealed that the i L ∼ c a linearity is altered from the predication of the conventional voltammetric theory as the size of electrode approaches nanometer scales (e. g.,