First-principles studies of electrophilic molecules on the carbon nanotubes

Various approaches have been made to separate semiconducting carbon nanotubes (CNTs) from metallic ones including chemical treatments. Recently we have demonstrated that some electrophilic molecules, such as 2,4,6-triphenylpyrylium tetrafluoroborate (2,4,6-TPPT) and 1,3-benzodithiolylium tetrafluoroborate (1,3-BDYT), preferentially interact with metallic CNTs. In this study, we present systematic theoretical studies on the interactions between the CNTs and these electrophilic molecules, using density functional theory. It was found that 2,4,6-TPPT and 1,3-BDYT interact with SWNT via noncovalent and covalent bindings, respectively. We have also found that 1,3-BDYT tends to be more strongly bound to the metallic SWNT of the smaller diameter. However, 2,4,6-TPPT tends to interact with CNTs via π-π interaction with very small binding energies, regardless of chiralities and diameters.