Carbonaceous impurities in carbon nanotubes are responsible for accelerated electrochemistry of cytochrome c.

There have been many reports on the excellent electrocatalytic properties of carbon nanotubes toward many substrates. Here, we wish to address and investigate the apparent "good promotion" of the electron transfer to cytochrome c as previously shown and attributed to the electrocatalytic properties of carbon nanotubes (Wang et al. Anal. Chem. 2002, 74, 1993). We will show here that the observed electrocatalytic effect toward this probe could be mainly attributed to the carbonaceous impurities present within the carbon nanotubes samples, instead of the carbon nanotubes themselves.