A density functional study of the 13C NMR chemical shifts in fluorinated single-walled carbon nanotubes.

The (13)C NMR chemical shifts of fluorinated semiconducting single-walled carbon nanotubes (SWNTs) were computed using a gaugeincluding projectoraugmented plane wave (GIPAW) density functional method. The chemical shifts of the fluorinated carbons (C(alpha)) were rather insensitive to the degree and pattern of functionalization, as well as to the nanotube radius. The calculated shifts were typically between 82 and 84 ppm, which is in excellent agreement with a recent experimental value of 83.5 ppm. Because of the insensitivity of the shifts to details of the nanotube's electronic structure and diameter, the NMR signals of the C(alpha) carbons are a useful indicator of the degree of functionalization in a heterogeneous bulk sample. At high degrees of functionalization, the shifts of atoms neighboring C(alpha) might also be useful indicators of the functionalization pattern.