The present invention is generally directed to new liquid-liquid
extraction methods for the length-based separation of carbon nanotubes
(CNTs) and other 1-dimensional nanostructures. In some embodiments, such
methods are directed to separating SWNTs on the basis of their length,
wherein such methods comprise the steps of: (a) functionalizing SWNTs to
form functionalized SWNTs with ionizable functional moieties; (b)
dissolving said functionalized SWNTs in a polar solvent to form a polar
phase; (c) dissolving a substoichiometric (relative to the amount of
ionizable functional moieties present on the SWNTs) amount of a phase
transfer agent in a non-polar solvent to form a non-polar phase; (d)
combining the polar and non-polar phases to form a bi-phase mixture; (e)
adding a cationic donor species to the bi-phase mixture; and (f)
agitating the bi-phase mixture to effect the preferential transport of
short SWNTs into the non-polar phase such that the non-polar phase is
enriched in short SWNTs and the polar phase is enriched in longer SWNTs.
In other embodiments, analogous methods are used for the length-based
separation of any type of CNT, and more generally, for any type of
1-dimensional nanostructure.