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 CF0.05 to CF0.32, and F2 treatment gives compositions in the range CF0.04 and CF0.37. 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.