Adsorption of CF4 on the internal and external surfaces of opened single-walled carbon nanotubes: A vibrational spectroscopy study
Infrared spectroscopy has been used to make the first experimental discrimination between molecules bound by physisorption on the exterior surface of carbon single-walled nanotubes (SWNTs) and molecules bound in the interior. In addition, the selective displacement of the internally bound molecules has been observed as a second adsorbate is added. SWNTs were opened by oxidative treatment with O3 at room temperature, followed by heating in a vacuum to 873 K. It was found that, at 133 K and 0.033 Torr, CF4 adsorbs on closed SWNTs, exhibiting its ν3 asymmetric stretching mode at 1267 cm-1 (red shift relative to the gas phase, 15 cm-1). Adsorption on the nanotube exterior is accompanied by adsorption in the interior in the case of opened SWNTs. Internally bound CF4 exhibits its ν3 mode at 1247 cm-1 (red shift relative to the gas phase, 35 cm-1). It was shown that, at 133 K, Xe preferentially displaces internally bound CF4 species, and this counterintuitive observation was confirmed by molecular simulations. The confinement of CF4 inside (10,10) single-walled carbon nanotubes does not result in the production of lattice modes that are observed in large 3D ensembles of CF4.
Byl, Oleg, Petro Kondratyuk, Scott T. Forth, Stephen A. FitzGerald, et al. 2003. "Adsorption of CF4 on the internal and external surfaces of opened single-walled carbon nanotubes: A vibrational spectroscopy study." Journal of the American Chemical Society 125(19): 5889-5896.
American Chemical Society
Journal of the American Chemical Society
Physics and Astronomy