Solubilization of Oxidized Single-Walled Carbon Nanotubes in Organic and Aqueous Solvents through Organic Derivatization

The solubilization of oxidized carbon nanotubes has been achieved through derivatization using a functionalized organic crown ether. The resultant synthesized adduct yielded concentrations of dissolved nanotubes on the order of ∼1 g/L in water as well as in methanol, according to optical measurements. The nanotube-crown ether adduct can be readily redissolved in 10 different organic solvents at substantially high concentrations. Characterization of these solubilized adducts was performed with ¹H NMR spectroscopy; ⁷Li NMR was also used to examine the ability of the crown ether's macrocyclic ring to bind Li⁺ ions. The solutions were further analyzed using UV-visible, photoluminescence, and FT-IR spectroscopies and were structurally characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). Adduct formation likely results from a noncovalent chemical interaction between carboxylic groups on the oxidized tubes and amine moieties attached to the side chain of the crown ether derivative.