Covalent modification of carbon surfaces with cyclodextrins by mediated oxidation of β-cyclodextrin monoanions

Abstract

The covalent grafting of glassy carbon and highly oriented pyrolytic graphite with cyclodextrins is reported in this work. The modification procedure is based in the concept that oxidation of organic anions generates radicals which react with carbon surfaces. These radical species are generated through a redox catalysis mechanism involving the formation of ferrocenium ion, which in turn oxidizes the cyclodextrin monoanion to afford an oxygen-centered free radical that ultimately reacts either in solution or with the surface, affording a strong attachment of cyclodextrin molecules to the carbon surface. The intervention of this radical was established from spectroelectrochemical EPR experiments. Atomic force microscopy imaging showed that the attached organic layer is thick while cyclic voltammetry experiments confirmed that this modified surface behaves as an ultramicroelectrode array. This kind of modification allows incorporate cyclodextrin to an electrode surface without a binder, making the modified electrode useful to be tested in forthcoming sensor studies.