Low-potential amperometric determination of hydrogen peroxide with a carbon paste electrode modified with nanostructured cryptomelane-type manganese oxides

Nanostructured. cryptomelane-type manganese oxides were synthesized, characterized, and evaluated for chemical sensing. Cryp-tomelane-type manganese oxides are nanofibrous crystals with sub-nanometer open tunnels that provide a unique property for sensing applications. Carbon paste electrodes (CPEs), modified with the nanostructured cryptomelane-type manganese oxides, were investigated for amperometric detection of hydrogen peroxide. With an operating potential of +0.3 V versus Ag/AgCl, H2O2 produces catalytic oxidation currents at the modified CPE, which can be exploited for quantitative determinations. The amperometric signals are linearly proportional to H2O2 concentration in the range 1.0 X 10(-4) -6.9 x 10(-4) M with a correlation coefficient of 0.995 (n = 7). At a signal-to-noise ratio of 3, a detection limit of 2 muM can be observed for the CPE modified with 5.5 wt% cryptomelane-type manganese oxides. In addition, the sensor has a good stability and reproducibility. The construction and renewal are simple and inexpensive. A possible response mechanism was proposed and discussed. The significant electrocatalytic activity of the modified CPE may result from the nanostructure of cryptomelane-type manganese oxides. (C) 2004 Elsevier B.V. All rights reserved.