Bioelectrochemistry and enzymatic activity of glucose oxidase immobilized onto the bamboo-shaped CNx nanotubes

The novel bamboo-shaped CNx nanotubes, synthesized by nitrogen atoms doping into carbon nanotubes, were used for the immobilization of a relatively large enzyme glucose oxidase (GO(x)) and its bioelectrochemical studies. The morphologies and adsorptions of GO(x) immobilization onto CNx nanotubes were clearly observed by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Electrochemical impedance spectroscopy (EIS) was also used to feature the GO(x) adsorbed onto the surface of CNx nanotubes. The immobilized GO(x) incorporated into CNx nanotubes films exhibited a well-defined nearly reversible cyclic voltammetric peaks for the electroactive centers of GO(x) and a fast heterogeneous electron transfer rate with the rate constant (K-s) of 1.96 s(-1). The immobilized GOx onto the CNx nanotubes exhibited its bioelectrocatalytic activity for the oxidation of glucose. The obtained results suggest that with a large amount of defective/active sites on the tube surfaces, a special bamboo structure and a suitable C-N microenvironment introduced by nitrogen doping, CNx nanotubes could not only facilitate the direct electron transfer between the enzyme and electrode, but also retain the high enzyme loading and the enzymatic bioactivity. (C) 2005 Elsevier Ltd. All rights reserved.