Comparative Study of SWCNT Fluorination by Atomic and Molecular Fluorine

Single-wall carbon nanotubes (SWCNTs) are fluorinated around 200 °C with molecular fluorine (F₂) and xenon difluoride (XeF₂) as fluorination agents. In this latter case, fluorination is carried out by atomic fluorine F^• generated by the thermal decomposition of gaseous XeF₂ on the nanotube surface. XeF₂ treatment results in stoichiometries from CF_0.05 to CF_0.32, and F₂ treatment gives compositions in the range CF_0.04 and CF_0.37. Transmission electronic microscopy (TEM), solid state Nuclear Magnetic Resonance (NMR), Raman scattering and Optical Absorption (AO) studies demonstrate that different fluorination mechanisms occur using molecular fluorine (F₂) and atomic fluorine (F^•). Atomic fluorine results in less sample damage and a more homogeneous fluorine distribution over the SWCNT surface than F₂. This is explained via DFT calculations showing that HF catalyzed F₂ deposition necessarily leads to highly fluorinated domain formation whereas F^• addition occurs spontaneously at the initial species arrival site