Attachment of Nitrogen and Oxygen Centered Radicals to Single-Walled Carbon Nanotube Salts

Carbon nanotube salts, prepared by treating single-walled carbon nanotubes (SWNTs) with lithium in liquid ammonia, react with N-halosuccinimide by electron transfer to generate transient radical anions that yield succinimidyl radicals and halide anions. Similarly, alkyl peroxides, when treated with SWNT salts, give rise to alkoxy radicals and alkoxides. The free radicals add to the sidewalls of nanotube salts to form succinimidyl and alkoxy derivatized SWNTs. The functionalized SWNTs can then be converted to amino and hydroxyl SWNTs by hydrolysis with hydrazine or with fuming sulfuric acid, respectively. Hydrolysis of alkoxy derivatized SWNTs with D2O/D2SO4 led to the deuterated analogue of hydroxy SWNT, as shown by Fourier transform infrared (FTIR) spectroscopy. These reactions constitute a two-step synthesis of aminated and hydroxylated SWNTs. Covalent sidewall functionalization was confirmed by thermal gravimetric analysis (TGA), Raman spectroscopy, FTIR spectroscopy, and high-resolution transmission electron microscopy (HRTEM). Aminated and hydroxylated SWNTs were characterized by FTIR and X-ray photoelectron spectroscopy (XPS).