Cylindrical Nanopore Electrode and Its Application to the Study of Electrochemical Reaction in Several Hundred Attoliter Volume

A method to fabricate cylindrical nanopore electrodes is presented. The volume of the cavity formed in the cylindrical nanopore electrode can be as small as several hundred attoliters. It has been characterized by using scanning electron microscopy and electrochemical methods. Our results show that the radius of the cavity can affect the diffusion coefficient of a redox species in the cavity. The cylindrical nanopore electrode has also been used to study charge transfer across the interface between an aqueous phase of several hundred attoliters in volume and a bulk chloroform phase. Compared with the same charge-transfer reaction across the interface between a bulk aqueous phase and a bulk chloroform phase, the potential of the charge-transfer reaction has a negative shift. The effect of the phase ratio on the distribution of the supporting electrolyte in the aqueous and organic phases has been used to explain the shift.