Noncovalent Functionalization with Alkali Metal to Separate Semiconducting from Metallic Carbon Nanotubes: A Theoretical Study

Despite intense studies of carbon nanotubes for decades, the separation of semiconducting and metallic single-walled carbon nanotubes (SWNTs) remains to be one of the most important tasks to be resolved. Here we demonstrate that a K atom binds the semiconducting SWNTs more strongly than the metallic SWNTs, while this binding strength hierarchy is reversed for a K + ion, consistent with experimental reports. This was shown by first-principles calculations, which properly describe the van der Waals interactions, and the origin of such results is explained. These results could be exploited as useful guidance toward separating semiconducting and metallic SWNTs via noncovalent functionalization.