Theoretical Study of Single-Wall Carbon Nanotubes Functionalization: Reaction Mechanisms and Raman Characterization

Functionalization of single-wall carbon nanotubes (SWCNTs) may enable separation by chirality or diameter. For example, electronic structure tailoring by chemical functionalization was recently demonstrated using water-soluble diazonium salts (Strano et al., Science, 2003). In our work, applying density functional theory calculations, we examined the reaction pathways for C(5,5) and C(10,0) SWCNTs, functionalized with a 4-chloro-phenyl group. Our results show that a charge-transfer-complex is involved in the functionalization, providing an understanding of experimental observations. At the same time, to avoid misconceptions, it is important to validate theoretical models used in studying functionalization, for example, by comparison with experimental Raman spectra shifts. As the upshift of the Raman breathing modes in carboxy-SWCNTs was well characterized, we investigated changes in the electronic structures, as well as the effects of intertube interactions in SWCNT bundles for this system. The calculated interaction energies and charge transfer are consistent with the small experimental upshift.