The reactivity of perfect and defective single-wall carbon nanotubes with the SH group was investigated using first-principles periodic calculations. The presence of Stone-Wales defect sites significantly increased the reactivity of single-walled carbon nanotubes against the thiol group. The most reactive site for the addition of the SH radical was the single vacancy defect; the sulfur atom reconstructed the single-walled carbon nanotubes framework and the hydrogen atom became attached to a carbon atom. The cluster model calculations performed for perfect single-walled carbon nanotubes confirmed a very low reactivity with the thiol group, even for the small diameter and metallic single-walled carbon nanotubes. The reaction between the perfect single-walled carbon nanotube and SH was thermodynamically unfavorable. The different reactivities observed for perfect and defective single-walled carbon nanotubes suggested that the SH group could be employed to perform a chemical labeling of the defect sites present in carbon nanotubes. The SH radical group was quite unique because, even though it had an unpaired electron, it did not react with sp2 carbon frameworks, unless they have defects or curvature similar to C60. The results were discussed in terms of experimental data on thiolated single-walled carbon nanotubes. It was possible to explain the transmission electron microscopic images of thiolated nanotubes and the lack of reactivity at the tips. A possible route for synthesizing sulfur-doped single-walled carbon nanotubes using thiol groups and their electronic properties was suggested.

Labeling the Defects of Carbon Nanotubes with Thiol Groups. P.A.Denis, J.S.Gancheff: Journal of Materials Science, 2010, 45[4], 1039-45