Electrocatalytic oxidation of NADH with Meldola's blue functionalized carbon nanotubes electrodes

Meldola's blue (MB) functionalized carbon nanotubes (CNT) nanocomposite film (MB/CNT) electrode was prepared by non-covalent adsorbing MB on the surface of a carbon nanotubes modified glassy carbon electrode (CNT/GCE). Electrochemical behaviors of the resulting electrode were investigated thoroughly with cyclic voltammetry in the potential range of −0.6 to 0.2 V, and two well-defined redox couples were clearly visualized. We also studied the electron transfer kinetics of MB loaded on CNT (MB/CNT) in comparison with that of MB on conventional graphite powder (MB/GP). The heterogeneous electron transfer rate constant (ks) of MB/CNT was calculated to be about three times larger than that of MB/GP. The accelerated electron transfer kinetics was attributed to the unique electrical and nanostructural properties of CNT supports as well as the interaction between MB and CNT. In connection with the oxidation of nicotinamide adenine dinucleotide (NADH), excellent electrocatalytic activities were observed at MB/CNT/GCE compared with MB/GP modified glassy carbon electrode (MB/GP/GCE). Based on the results, a new NADH sensor was successfully established using the MB/CNT/GCE. Under a lower operation potential of −0.1 V, NADH could be detected linearly up to a concentration of 500 μM with an extremely lower detection limit of 0.048 ± 0.02 μM estimated at a signal-to-noise ratio of 3. Sensitivity, selectivity, reproducibility and stability of the NADH sensor were also investigated and the main analytical data were also compared with those obtained with the MB/GP/GCE.