Voltammetric measurements at the surface of cotton: Absorption and catalase reactivity of a dinuclear manganese complex

Voltammetric measurements at the surface of cotton fabric were conducted after impregnating the surface of the textile with graphite flakes. The resulting conducting surface contact was connected to a conventional basal plane pyrolytic graphite substrate electrode and employed both in stagnant solution and in rotating disc voltammetry mode. Diffusion through the immobilized cotton sample (inter-fiber) is probed with the aqueous Fe(CN)(6)(4-/3-) redox system. With a small amount of platinum immobilized at the cotton surface, catalase reactivity toward hydrogen peroxide was observed and used to further quantify the diffusion (intra- and inter-fiber) into the reactive zone at the graphite-cotton interface. A well-known catalase model system, the dinuclear manganese metal complex [Mn(IV)(2)(mu-O)(3)L-2](PF6)(2) (with L = 1,4,7-trimethyl-1,4,7-triazacyclononane), is investigated in aqueous 0.1 M carbonate buffer at pH 9.8 in contact with cotton fabric. Absorption of the metal complex is monitored and quantified by voltammetric methods. A Langmurian binding constant of approximately K = 2 x 10(3) M-1 was determined. Voltammetric measurements of the adsorbed metal complex reveal strong absorption and chemically irreversible reduction characteristics similar to those observed in solution. In the presence of hydrogen peroxide, catalyst coverage dependent anodic catalase activity was observed approximately following the rate law rate = k[catalyst](surface)[H2O2](solution) and with k = 3 x 10(4) dm(3) s(-1) mol(-1). The catalyst reactivity was modified by the presence of cotton.