Electron transfer across the single micro-water-droplet|oil interface using microcapillary injection and microelectrode methods

Electron transfer (ET) between a hexacyanoferrate(III) ion in a single micro-water-droplet and a ferrocene derivative (Fc), such as decamethylferrocene, in 2-nitrophenyl octyl ether was studied using microcapillary injection and microelectrochemical techniques. The overall ET rate constant increased with the decreasing Gibbs energy (ΔG), consisting of the Galvani potential between the water and oil phases and the redox potential difference of the solutes, and was saturated at a ΔG value less than −15 kJ mol−1. The ΔG dependence of the overall ET rate was discussed in terms of the interfacial ET coupled with the microscopic diffusion of Fc in the vicinity of the water|oil interface.