Diffusion of ferrocene methanol in super-cooled aqueous solutions using cylindrical microelectrodes

The diffusion of ferrocene methanol in super-cooled aqueous solutions containing sucrose has been studied, using disk and cylindrical microelectrodes, over a wide viscosity range. The solution viscosity and the reduced temperature T/Tg (Tg being the glass transition temperature) were varied by changing the sucrose concentration and the temperature of the system. The voltammetric limiting current obtained with a disk microelectrode and the i(t) response on a cylindrical microelectrode after a potential step were used to determine diffusion coefficients from 7 × 10−6 cm2 s−1 down to 2 × 10−11 cm2 s−1. The electrochemical procedure described in this work allows a simple and accurate measurement of the dynamics of electroactive solutes in glass-forming liquids.