Methylene blue-zirconium phosphate-cellulose acetate hybrid membrane film attached to a platinum electrode and its application in electrocatalytic oxidation of NADH

Highly dispersed zirconium phosphate was prepared by reacting a cellulose acetate membrane film containing zirconium oxide (ZrO2 = 6.3 wt.%; 0.50 mmol g(-1) of the zirconium atom per gram of the material) with phosphoric acid. The resulting membrane film was reacted with methylene blue (MB) by an ion exchange reaction. The amount of the dye bonded to the surface was 0.15 mmol g(-1). High power decoupling magic angle spinning (HPDEC-MAS) P-31 NMR data indicated that Zr(HPO4)(2) is the species present on the membrane surface. Cyclic voltammetry experiments of the MB dye adsorbed onto CelZrP, carried out on a thin membrane of the material fixed on a platinum disk electrode, were obtained. The midpoint potential (E-m) of CelZrP/MB was -0.15 V The solution pH practically did not affect the midpoint potential of the adsorbed dye between pH 3 and 7. The modified electrode presented a reproducible response and it was chemically stable under various oxidation-reduction cycles. The electrode proved to be efficient to mediate the transfer for NADH oxidation. The apparent Michaelis-Menten constant, K-M(app), for the modified electrode showed an efficient interaction between dye and NADH. (C) 2002 Elsevier Science B.V. All rights reserved.