A C₆₀-embedded artificial bilayer membrane film electrode device: Phase-transition-dependent electrochemistry

We describe here regulated electrochemistry of C₆₀ embedded in a cast film of an artificial lipid, dibexadecyldimethylammonium poly(styrene sulfonate) (1) on an electrode, The X-ray diffraction diagram for a cast film of C₆₀/1 (molar ratio, 1/19) showed a diffraction peak at 2θ = 1.8° suggesting that the film forms multibilayer structure with the molecular layers tilting by 47° from the basal plane. Phase-transition temperature for a cast film of 1/C₆₀ (molar ratio, 1/19) in the presence of water determined by differential scanning calorimetry was 27°C, which was almost identical with that of the single component of 1. At temperatures above the phase transition, a cast film of C₆₀/1 on a basal plane pyrolytic graphite electrode in aqueous solution gave quasi-reversible two-consecutive one-electron-transfer processes leading to C₆₀^2- with the formal potential of E₁^0′ = -0.35 V and E₂^0′ = -0.99 V vs SCE corresponding to C₆₀/C₆₀^•- and C₆₀^•-/ C₆₀^2-, respectively. At temperatures below the phase-transition temperatures, the redox current for the electrode was very small or nondetectable. This temperature dependence was reversible; that is, temperature-driven "on-off" switching of C₆₀ electrochemistry was possible. The observed phenomenon would be applicable to C₆₀-derivatives, higher fullerenes, and metallofullerenes. The present study opens possibilities for the construction of fullerene/artificial lipid electrical devices based on the nature of self-organized lipid bilayer membranes.