Bipolar Electrochemistry on a Nanopore-Supported Platinum Nanoparticle Electrode

In this Technical Note, we describe a method to fabricate nanopore-supported Pt nanoparticle electrodes and their use in bipolar electrochemistry. A Pt nanoparticle is deposited on the orifice of a solid-state nanopore inside a focused-ion beam (FIB) system. Complete blockage of the nanopore with Pt metal forms a closed bipolar nanoparticle electrode whose size and shape can be tunable in one simple step. Nanoparticle electrodes and their arrays can be prepared on different substrates such as the tip of a glass pipet, a double-barrel pipet, and a freestanding silicon nitride membrane. Steady-state voltammetry can be performed on such nanoparticle electrodes via bipolar electrochemistry. Moreover, an array of Pt nanoparticles can be used for fluorescence-enabled electrochemical microscopy. Future use of highly advanced FIB systems may allow nanoparticles of <10 nm to be fabricated which may enable coupled electrochemical reactions of single redox molecules. Pipette-supported single particle electrodes may also find useful applications in high resolution imaging with nanoscale scanning electrochemical microscopy (SECM) and neurochemical analysis inside single cells.