On the free radical scavenging capability of carboxylated single-walled carbon nanotubes

Density functional theory calculations have been used to model the efficiency of carboxylated single-walled carbon nanotubes (SWCNT) to act as free radical scavengers, relative to that of their corresponding nonfunctionalized partners. The exergonicity of the reactions between carboxylated SWCNTs and the studied free radicals was found to be dependent on the site of functionalization as well as on the site of reaction. The major conclusion from this work is that carboxylated SWCNTs are at least as good, or even better, free radical scavengers than their nonfunctionalized partners. It is proposed that the presence of -COOH groups would increase the free radical scavenging activity of SWCNTs, provided that the coverage occurs in such an amount that there is enough free space on the walls for the reactions to take place. The reliability of the calculations reported in the present work has been tested by comparison with different levels of theory.