On SOCl2 hydrolysis at carbon nanotubes

The experimentally observed oxygen content increase in SOCl2 treated single-wall carbon nanotubes (SWCNTs) may be explained by the air moisture hydrolysis of the acid-chloride groups created at the structure defects as well as of SOCl2 molecules adsorbed at SWCNT sidewalls. The adsorption of SOCl2, and its hydrolysis products (HOSO2-,HSO3-andSO2) on coronene C24H12 as the simple SWCNT model has been studied at B3LYP/6-31+G∗∗ level of theory (with relevant hydrogen atoms augmented by diffusion functions as well). Whereas the adducts with neutral molecules exhibit weak interactions of sulphur (SOCl2 and SO2) or oxygen (SOCl2) atoms with π electron system of coronene, these interactions with cations are mediated via hydrogen bonds only. The optimal geometries indicate high affinity of all the adsorbed species to the structure defects (edges). The physisorption (especially of SOCl2 and SO2) produces a small gap, i.e. a tendency towards metallic character as seen in graphene sheets.