The effect of point defects upon the free-radical scavenging activity of armchair and zig-zag single-walled carbon nanotubes, through a radical adduct formation mechanism, was studied using density functional theory calculations. Single-walled carbon nanotubes with various vacancy, adatom and Stone-Wales defects were considered, as well as their pristine equivalents. All of the studied reactions were significantly exothermic and exergonic, which supported their viability. The presence of point defects in the carbon lattice of single-walled carbon nanotubes was predicted to increase their free-radical scavenging activity. The adatom and vacancy point defects, involving C atoms with dangling bonds, were expected to cause a larger increase in the single-walled carbon nanotube reactivity towards free radicals than were Stone-Wales and vacancy defects without C atoms with dangling bonds. The studied Stone-Wales point defect exhibited the largest site-dependent effect on the free-radical scavenging activity of single-walled carbon nanotubes. The presence of non-polar environments was not expected to change these trends. Characteristic infra-red bands in the 3300 and 900 to 1100/cm regions were attributed to the νO-H and νC-O vibrations of the OH radical adducts.

Influence of Point Defects on the Free-Radical Scavenging Capability of Single-Walled Carbon Nanotubes. A.Galano, M.Francisco-Marquez, A.Martínez: Journal of Physical Chemistry C, 2010, 114[18], 8302-8