Fluorination of single-walled carbon nanotubes using gaseous XeF_2

摘要

An original tuneable fluorination method has been used to obtain fluorinated Single-Walled carbon Nanotubes (SWNT). Gaseous xenon difluoride (XeF_2) is used as fluorinating agent at 120°C in order to increase the relative pressure of gaseous XeF_2; the fluorination occurs through the gas/solid reaction, i.e. XeF_2(g)/C. The quantities of SWNT and XeF_2 can be tuned in order to control the fluorination level. The obtained fluorinated SWNTs (F-SWNT), with various fluorination levels, were compared with the results of the direct process using elemental fluorine. Raw SWNT and fluorinated SWNT were studied by optical absorption (OA), photoluminescence (PL) and Raman scattering (laser excitations at 1064 nm, 514 nm and 458 nm) using aqueous suspensions or solid samples. The suspensions have been elaborated in D_20 with a surfactant. Optical measurements (OA and PL) show the influence of the fluorination on the optical properties of the SWNT through changes in the SWNT electronic structure. Changes in Raman Radial Breathing Modes (RBM) with the amount of fluorination have been discussed in terms of resonance for Raman scattering. Moreover, the evolution of the I_d/I_q ratio between the D-band (defect induced mode) and the G-band (tangential mode) is also studied as a function of the fluorinated level. Chemical selectivity of the fluorination is also investigated.