Theory of Microwell Arrays Performing as Generators–Collectors Based on a Single Bipolar Plane Electrode

Abstract

Electroanalytical arrays of microwells with increased sensitivity and virtual immunity to interferents have been previously reported by us. Such arrays were designed to be operated in a classical generator–collector mode but exhibited also similar properties when their common planar collector was left floating. This evidenced that the unbiased collector acted as a bipolar electrode. In this work, a theory is elaborated to investigate in great detail the generality of this phenomenon and its limits. This establishes that if the analyte pertains to a redox couple with relatively fast electron rate constants, the bipolar collector results to be almost as efficient as when biased, thus suppressing the need for a bi‐potentiostat with obvious gain for analytical applications. Conversely, if the analyte rate constant of electron transfer is small, efficient operation in a bipolar mode remains feasible but requires a drastic decrease of the microwell density in the array.

Focused-Ion-Beam-Milled Carbon Nanoelectrodes for Scanning Electrochemical Microscopy

“…The electrolysis of the tip-generated species, R, to the original redox species, O, at the large surface of a conductive outer wall is also driven at a diffusion-limited rate (34) as given by…”

Scanning Electrochemical Microscopy for the Electroless Deposition of Gold on Natural Pyrite: Effect of Ferric Ions

“…The possibility to grow further the gold deposit “vertically” at the micrometre scale, suggests that another scenario should be considered. In the SECM configuration the localized formation of coupled to the conductive properties of pyrite makes possible the reduction of at the pyrite surface (equation 4) concomitantly to the pyrite corrosion (equation 5) outside the area of the UME functioning as a bipolar electrode, according to a corrosion mechanism of pyrite already proposed …”

Unravelling the last milliseconds of an individual graphene nanoplatelet before impact with a Pt surface by bipolar electrochemistry

“…FcDM (species "R" in Figure 3A) is oxidized at the extremity of the GNP the furthest in solution while FcDM + (species "O" in Figure 3A) been evidenced with SECM tips approaching unbiased conducting substrates [42][43][44] as well as networks of micro-ring electrodes at the bottom of a well in proximity with a high-area gold layer that is not electrically connected to the ring electrodes and left floating at the potential of the solution. 45,46 To support our hypothesis, we performed 2D axial numerical simulations describing the oxidation of FcDM on the UME in presence of a spheroidal conducting GNP, as depicted in Figure 3A. We choose a prolate ellipsoid shape of GNP to allows for 2D simulations, while preserving the trends expected for a 3D system (see Electronic Supplementary Information).…”