Complexation-Induced Control of Electron Propagation Based on Bounded Diffusion through Nanopore-Tethered Ferrocenes

Abstract

This paper reports complexation-induced control of electron propagation based on bounded diffusion through ferrocene moieties that are covalently tethered onto nanopores (19 or 24 nm in diameter) derived from cylinder-forming polystyrene-poly(methylmethacrylate) diblock copolymers. The nanopores are oriented vertically and attach to a gold surface, and thus allow a faradaic current originating from the bounded diffusion to be measured using cyclic voltammetry. Such faradaic current decreases with increasing concentration of β-cyclodextrin (β-CD) in an aqueous solution, and recovers upon addition of excess 1-adamantanol as a competitive guest to the solution. These observations indicate that electron propagation can be reversibly inhibited by the formation of an inclusion complex with the surface-tethered redox moieties. Interestingly, the decrease in faradaic current is observed at an unexpectedly low β-CD concentration (ca. 1 × 10(-7) M) due to the enhanced partition of β-CD into the nanopores. These results will lead to designing highly sensitive molecular switches and electrochemical sensors based on the control of bounded diffusion by the host-guest chemistry of nanopore-tethered redox moieties.