First-principles studies on carbon nanotubes functionalized with azomethine ylides

Theoretical Studies based on density functional theory framework have been performed on covalently functionalized carbon nanotubes (NTs) with azomethine ylides using SIESTA and CPMD codes. In view of the binding energies, it is found that armchair tubes favor functional ization at C-C bonds slanted to the tube axes, whereas zigzag NTs prefer attachment of the ylides at segments parallel to the tube axes. It is also suggested that the geometry of pyrrolidine rings attached to NTs strongly depends on the binding segments. The dependency is attributed to the degree of pi-orbital alignment. Comparison of various functionalized derivatives on armchair tubes shows that the binding segments and atomic types at the segments significantly influence the electronic band structures near the Fermi energy. In metallic NTs, the covalent functionalization leads to opening of band gaps, whereas the effect of functional ization on the change of band gap energies is negligible for semiconducting NTs.