Distinct properties of single-wall carbon nanotubes with monovalent sidewall additions

Ab initio calculations reveal distinct electronic properties associated with functionalized single-wall carbon nanotubes (SWNTs) with monovalent sidewall additions. The metallic tubes are found to be more reactive than the semiconducting ones. The hybridization between the addend and the tube induces unique impurity states near the Fermi level. For semiconducting tubes the state is localized near the functionalized site with a characteristic length of 15 A. In contrast, the impurity state is extended and acts as a strong scattering centre in metallic tubes. This effect greatly hinders the ballistic transport of electrons along the metallic nanotubes. The characteristic dependence of the electronic states and the conductance on functional molecules provides possible pathways for chemical sensor applications and the band structure engineering.