Raman spectroscopic investigation of gas interactions with an aligned multiwalled carbon nanotube membrane

Raman spectroscopy has been used to investigate ethane, propane, and SF ₆ interactions with an aligned multiwalled carbon nanotube (MWNT) membrane. Pressures of 7.5-9.3 atm and temperatures of 293-333 K were examined for propane and SF ₆, whereas slightly lower temperatures (263-293 K) and pressures (6.7-7.5 atm) were used for ethane. Red-shifting and broadening is seen for the C-C stretching vibrations of the two hydrocarbons, as well as for the Aig symmetric vibration (v ₁) of SF ₆. These spectral features indicate that the interaction between the gas and the nanotube membrane is capable of perturbing molecular vibrations and creating red-shifted features. Control experiments done on polycrystalline graphite and a polystyrene blank indicate that this spectral behavior is unique to gases interacting with the nanotubes in the membrane.