Finite-Element Computer Simulations on Cyclic Voltammograms Measured at Recessed Nanodisk-Array Electrodes

Abstract

The characteristics of cyclic voltammograms (CVs) at recessed nanodisk-array electrodes (RNEs) were investigated using finiteelement computer simulations. Simulations were performed for RNEs based on planar electrodes coated with electricallyinsulating films comprising hexagonally-distributed, verticallyoriented cylindrical nanopores (12 nm in radius, 30 nm deep). CVs and concentration profiles of redox species were simulated by varying electrode spacing (2s) and the diffusion coefficient of a redox species within the nanopores (D pore ). For nm-scale s and large D pore , peak-shaped CVs with currents very similar to those at a film-free electrode were obtained due to the overlapping of diffusion layers extended from multiple electrodes. However, larger s and smaller D pore gave smaller peak currents, as the nanoscale electrodes limited the number of redox species to be reacted. Further increase in s offered sigmoidal CVs though s was small enough for the overlapping of diffusion layers. These trends were consistent with experimental CVs measured at RNEs.

Nanoporous Thin Films Formed from Photocleavable Diblock Copolymers on Gold Substrates Modified with Thiolate Self-Assembled Monolayers

“…This behavior contrasts with those seen from the other three substrates, which gave more sigmoidal voltammograms with smaller faradaic currents. The observation of the peak-shaped voltammograms typically indicates the presence of highly dense active nanopores that led to the overlapping of diffusion layers developed from individual electroactive underlying electrodes. , Alternatively, the faradaic currents of the peak-shaped voltammograms were smaller than those observed at a planar gold substrate of the identical geometric area (Figure a; depicted in purple), reflecting the partial blocking of the electrode surface by a nanoporous insulating layer. , The higher permeability and electroactivity obtained from nanoporous films on NH 2 -SAM reflect the vertical orientation of PEO microdomains enhanced at the interface, as suggested by the AFM data (see above).…”

Electrochemical sensing at nanoporous film‐coated electrodes

“…It should be pointed out that RNE-based sensors based on the former two principles discussed in Sections 4 and 5 measure faradaic currents controlled by the diffusion of electroactive solutes onto the underlying electrodes. In these detection principles, RNEs based on highly porous films may not be suitable for highly sensitive detection owing to the overlap of diffusion layers developed from the individual nanodisk electrodes: [59,60] Significant changes in diffusion-controlled faradaic signal can be obtained only when permeability is reduced at a sufficiently large fraction of nanopores. [60]…”

“…In these detection principles, RNEs based on highly porous films may not be suitable for highly sensitive detection owing to the overlap of diffusion layers developed from the individual nanodisk electrodes: [59,60] Significant changes in diffusion-controlled faradaic signal can be obtained only when permeability is reduced at a sufficiently large fraction of nanopores. [60]…”

Block Copolymer‐Derived Monolithic Polymer Films and Membranes Comprising Self‐Organized Cylindrical Nanopores for Chemical Sensing and Separations

“…Owing to the high porosity, electrodes coated with these nanoporous films usually exhibit peak-shaped voltammograms that reflect the overlap of diffusion layers developed from individual nanopores. [67,68,72] …”

“…On the other hand, these high-porosity films may not be ideal to design permeability-based sensors for trace analysis because the observation of current signals requires permeability changes at the majority of the nanopores. [72] In contrast, a single pore membrane permits the detection of the penetration events of individual particles as transient permeability changes of the pore, which is known as the resistive-pulse technique. [75] So far, RNEs based on PS-b-PMMA-derived nanoporous films (ca.…”