Electrochemical analysis of ferrocene in bicontinuous microemulsions using β- cyclodextrin modified monolayer graphene electrodes

A monolayer graphene electrode modified with β-cyclodextrin (β-CD) was produced via a one-step reaction using an originally synthesized pyrene derivative of β-CD (py-β-CD). A py-β-CD-modified graphene electrode with a high modification density exceeding a coverage of 0.5 was obtained. Using this electrode, the electrochemical behaviors of water-insoluble ferrocene (Fc) and of a water-soluble ferrocene derivative in a bicontinuous microemulsion (BME) solution, consisting of a phosphate buffer (pH = 7.4), sodium dodecyl sulfate (SDS), 2-butanol, and toluene, were analyzed to investigate the effects of β-CD modification on the redox reactions of these species. In the reduction reaction of water-insoluble Fc, almost no peak was observed for the unmodified graphene electrode, whereas a high peak current increase was observed for the β-CD-modified electrode. The mechanism of the increase in the peak current of the reduction reaction can be derived from many small water domains formed around the β-CD molecules on the graphene surface. These water domains form many oil–water interfaces on the surface of the graphene electrode, which act as an [Fc] +1 concentration field by interacting with SDS.