Debundling of single-walled carbon nanotubes by a nanoball-penetrating method

Water-based FePt nanoparticles (NPs) have been used to disperse acid-treated HiPCO single-walled carbon nanotubes (SWNTs) in TMAOH solution under mild experimental conditions. The result shows that seriously aggregated SWNTs with bundle sizes from 20 to similar to 30 nm can be exfoliated into individually dispersed tubes in water while their intrinsic chemical properties and long lengths are kept intact. A novel nanoball-penetrating method is proposed, and the dispersion and exfoliation mechanism is discussed to explain the debundling results. Electrostatic interaction between (CH3)(4)N+ and carboxyl groups on SWNTs decreasing the van der Waals force of the bundles, deep penetration of FePt NPs into the gaps of SAINT ropes, and repulsive interaction between negatively charged SWNTs and FePt NPs all contribute to the final efficient exfoliation. More than 50% of SWNTs can be debundled into individually dispersed nanotubes under optimum conditions. Raman scattering spectroscopy used to characterize the properties of SWNTs proved that the exfoliation process is noncovalent by nature. The dispersion and debundled process can be easily scaled up at low cost, and this will allow for the investigation of various nanotube-based nanocomposites and will pave the way for varied applications of SWNTs on a large scale.