Comparative Study of SWCNT Fluorination by Atomic and Molecular Fluorine

Single-wall carbon nanotubes (SWCNTs) are fluorinated around 200 °C with molecular fluorine (F 2 ) and xenon difluoride (XeF 2 ) as fluorination agents. In this latter case, fluorination is carried out by atomic fluorine F • generated by the thermal decomposition of gaseous XeF 2 on the nanotube surface. XeF 2 treatment results in stoichiometries from CF 0.05 to CF 0.32, and F 2 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 (F 2 ) and atomic fluorine (F • ). Atomic fluorine results in less sample damage and a more homogeneous fluorine distribution over the SWCNT surface than F 2 . This is explained via DFT calculations showing that HF catalyzed F 2 deposition necessarily leads to highly fluorinated domain formation whereas F • addition occurs spontaneously at the initial species arrival site.