Amperometric determination of hydrogen peroxide by functionalized carbon nanotubes through EDC/NHS coupling chemistry

The electrochemistry of the redox mediator Toluidine blue (TB) which was covalently linked to the carboxyl group of the multiwalled carbon nanotubes (MWNTs) by coupling reactions, in which N-hydroxysuccinimide was used to assist 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride catalyzed amidation reaction is described. The results from cyclic voltammetry (CV) and amperometry suggested that the redox mediator is linked to the surface of the MWNTs and the nanotubes showed an obvious promotion for the direct electron-transfer between the redox mediator and the electrode. A couple of well-defined redox peak of TB was observed in a phosphate buffer solution (pH 7.0). The redox mediator immobilized to MWNTs exhibits remarkable electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). The analytical applicability of the modified electrode for the determination of hydrogen peroxide was examined. A linear response in the concentration range of 6.8 x 10(-7)-3.4 x 10(-2) M (r = 0.9958) was obtained with detection limit of 3.4 x 10(-7) M for the determination of hydrogen peroxide. The modified electrode has advantages of being highly stable, sensitive, ease of construction and use.