The electrochemical behavior of a film of single-wall carbon nanotubes (SWNTs) functionalized with carboxylic acid groups was studied extensively on a glassy carbon (GC) electrode. One stable couple corresponding to the redox of the carboxylic acid group, which was supported by XPS and IR experiments, was observed. The electrode process involved four electrons, while the rate-determining step was a one-electron reduction. The SWNT film-modified electrode showed favorable electrocatalytic behavior toward the oxidation of biomolecules such as dopamine, epinephrine, and ascorbic acid.

The electrochemistry of horse heart cytochrome c was studied by cyclic voltammetry at a glassy carbon electrode modified with single-wall carbon nanotubes (SWNTs). A pair of well-defined redox waves was obtained in cytochrome c aqueous solution at an activated SWNT film-modified electrode. The optimal conditions for activating the SWNT film-modified electrode has been determined. The electrode reaction of cytochrome c is a diffusion-controlled process. The peak current increases linearly with the concentration of cytochrome c in the range from 3.0 x 10(-5)-7.0 x 10(-4) M. The detection limit is 1.0 x 10(-5) M. The activated SWNT film was characterized by scanning electron microscopy. Furthermore, interaction of cytochrome c with adenine was characterized by electrochemical and spectral methods.

The voltammetric behavior of norepinephrine (NE) was studied at a glassy carbon (GC) electrode modified with single wall carbon nanotubes (SWNTs). In pH 5.72 B‐R buffer solution, the SWNT‐modified electrode shows high electrocatalytic activity toward NE oxidation. One well‐defined reversible redox couple is obtained at scan rates lower than 0.15 V s−1. The peak current increases linearly with the concentration of NE in the range of 1.0×10−5 ‐ 1.1×10−3 mol dm−3. The detection limit is 6.0×10−6 mol dm−3 and the diffusion coefficient (D) of NE is 8.53×10−6 cm2 s−1. The SWNT was characterized with scanning electron microscope (SEM). Furthermore, the SWNT‐modified electrode has favorable electrocatalytic activity with dopamine, epinephrine, and ascorbic acid.

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Single-wall carbon nanotubes (SWNTs) can be used as an electrochemical probe to study the electrochemical oxidation of DNA, two voltammetric oxidation peaks corresponding to electrochemical oxidation of guanine and adenine residues in DNA could be observed, demonstrating a new potential application of SWNTs in DNA analysis. Compared to other types of electrode materials, the electrochemical response of natural DNA was greatly enhanced at the SWNT-modified electrode. This method can be used to investigate the interaction of SWNTs with DNA.

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