It was reported that carbon nanotube (CNT) was functionalized with the electroactive Nile Blue (NB), which was a phenoxazine dye, by a method of adsorption to form an NB-CNT nanocomposite. The spectroscopic results showed that NB can be rapidly and effectively adsorbed on the surface of CNT with high stability without changing the native structure of NB and the structure properties of CNT. Moreover, it was shown that the dispersion ability of CNT in aqueous solution had a significant improvement after CNT was functionalized with NB even at a level of high concentration, for example 5 mg of NB-CNT per 1 mL of H₂O. The NB-CNT/GC electrode was fabricated by modifying NB-CNT nanocomposite on the GC electrode surface and its electrochemical properties were investigated by cyclic voltammetry. The cyclic voltammetric results indicated that CNT could improve the electrochemical behavior of NB and greatly enhance its redox peak currents. While the NB-CNT/GC electrode exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of (－0.422±0.002) V (vs. SCE, 0.1 mol/L PBS, pH 7.0), which was almost independent of the scan rates, for electrochemical reaction of NB monomer, the redox peak potential of NB polymer located at about －0.191 V. The experimental results also demonstrated that NB and CNT could synergistically catalyze the electrochemical oxidation of NADH (β-nicotinamide adenine dinucleotide, reduced form) and NB-CNT exhibited a high performance with lowering the overpotential by more than 560 mV. The NB-CNT/GC electrode could effectively sense the concentration of NADH, which was produced during the process of oxidation of substrate (for example ethanol) catalyzed by dehydrogenase (for example alcohol dehydrogenase). The presented method for functionalization of CNT had several advantages, such as rapid and facile CNT functionalization, easy electrode fabrication, high electrocatalytic activity, etc., and could be used for fabrication of electrochemical biosensor based on dehydrogenase.

Key words: carbon nanotube, chemically modified electrode, functionalized carbon nanotube, electrocatalysis, NADH