Comparison of the electrochemical reactivity of carbon nanotubes paste electrodes with different types of multiwalled carbon nanotubes

Carbon nanotubes (CNTs) are widely used in electrochemical studies. It is reported that CNTs with different source and dispersed in different agents [1] yield significant difference of electrochemical reactivity. Here we report oil the electrochemical performance of CNTs paste electrodes (CNTPEs) prepared by multiwalled carbon nanotubes (MWNTs) with different diameters, lengths and functional groups. The resulting electrodes exhibit remarkable different electrochemical reactivity towards redox molecules such as NADH and K-3[Fe(CN)(6)]. It is found that CNTPEs prepared by MWNTs with 20-30 nm diameter show highest catalysis to NADH oxidation, while CNTPEs prepared by MWNTs with carboxylate groups have best electron-transfer rate (The peak-peak separation (Delta E-p) is +0.108 V for MWNTs with carboxylate groups, +0.155 V for normal MWNTs, and +0.174 V for short MWNTs) but weak catalysis towards oxidation of NADH owing to the hydrophilicity of carboxylate groups. The electrochemical reactivity depends on the lengths of CNTs to some extent. The 'long' CNTs perform better in our study (The oxidation signals of NADH appear below +039 V for 'long' CNTs and above +0.46 V for the 'short' one totally). Readers may get some directions from this article while choose CNTs for electrochemical study.