Separation of metallic and semiconducting single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNTs) can be either metallic (m) or semiconducting (s) depending on their atomic structures. Most practical applications of SWCNTs would require uniformly m– or s–SWCNTs. However, none of current synthesis methods can successfully produce SWCNTs with uniform metallicity. Intense research efforts have been devoted to post-synthetic separation of SWCNTs based on their metallicity. We begin this chapter by introducing the relation between SWCNT metallicity and their structures. Next, we describe separation approaches according to different electric conductivity and dielectric constants. We also discuss various chemical methods to augment the difference between m– and s– (m/s–) SWCNTs, followed by illustrating separation techniques for chemically modified SWCNTs. Last but not least, we review methodologies for evaluating abundances of SWCNTs with different metallicities.