Chemical functionalization of carbon nanotubes with Stone-Wales defects, by carboxyl (COOH) groups, was investigated using density functional calculations. Due to the localized donor states introduced by the Stone-Wales defect, the binding of the COOH group to the defective carbon nanotube was stronger than that to the perfect one. A quasi-tetrahedral bonding configuration of carbon atoms, indicating sp3 hybrid bonding, was formed in the adsorption site. Charge distribution analysis showed that, in comparison with benzoic acid, the localized or delocalized π-states on the nanotube, would affect the polarities of chemical bonds of the COOH group without losing acidity. It was found that the double-adsorption system (two COOH groups adsorbed on two carbon atoms of the Stone-Wales defect) was more energetically favorable than the mono-adsorption one. The adsorption of COOH groups led to a significant change in the electronic states around the Fermi level. This was advantageous to electrical conductivity.

Chemical Functionalization of Carbon Nanotubes by Carboxyl Groups on Stone-Wales Defects: a Density Functional Theory Study. C.Wang, G.Zhou, H.Liu, J.Wu, Y.Qiu, B.L.Gu, W.Duan: Journal of Physical Chemistry B, 2006, 110[21], 10266-71