Functionalization of individual ultra-short single-walled carbon nanotubes

We report the functionalization of individual ultra-short (20-80 nm lengths) single-walled carbon nanotubes (US-tubes) via in situ Bingel cyclopropanation. Upon chemical reduction (K degrees/THF) of bundled US-tubes, the bundling forces are electrostatically overcome to yield single, negatively charged US-tubes in solution. These single US-tubes can then be functionalized with malonic acid bis-(3-tert-butoxycarbonylaminopropyl) ester using Bingel chemistry (CBr4/DBU) to yield 4-5 adducts nm(-1), as determined by x-ray photoelectron spectroscopy (XPS). The derivatized US-tubes remain as individuals after functionalization and charge quenching. Thermogravimetric analysis (TGA) and solid-state NMR spectroscopy confirmed covalent attachment of the adducts and indicated tight wrapping of the adduct arms about the US-tubes. The resulting debundled and derivatized US-tubes serve as a prototype single-molecule-like 'capsule' for the containment and delivery of medically-useful payloads.