Size-dependent efficiency of electron transfer at suspended ferrocenyl jumbo particles

Ferrocenylmethanol acrylate (FcMA)-immobilized polystyrene latex particles were synthesized by copolymerizing FcMA and styrene in the presence of polystyrene latex suspensions with eight different diameters ranging from 0.084 to 1.7 μm. The amounts of the ferrocenyl moiety loaded on one particle were proportional to the radii, a. The proportionality suggests the uniform distribution of the ferrocenyl moiety over the particle, of which concentration was 0.18 M. The aqueous suspensions, which were stable in the presence of a surfactant, exhibited reversible voltammetric waves for the ferrocenyl moiety. The peak current was controlled by diffusion of the latex particles. The efficiency of the reaction was obtained from the ratio of the observed current to the theoretical one which was estimated from the number of the ferrocenyl moieties and the diffusion coefficient of the particle by the Stokes–Einstein relation. The ratio was proportional to a−0.47, whereas it might be a0 for an ideal particle without any size effect. This relation was explained in terms of the contribution of rotational diffusion of redox particles.