AVS 50th International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoA

Paper AS-MoA3
Adsorption of CF@sub 4@ on Opened Single Walled Carbon Nanotubes

Monday, November 3, 2003, 2:40 pm, Room 324/325

Session: Nanotube and Nanoparticle Characterization
Presenter: O. Byl, University of Pittsburgh
Authors: O. Byl, University of Pittsburgh
P. Kondratyuk, University of Pittsburgh
L. Chen, University of Pittsburgh
J.K. Johnson, University of Pittsburgh
J.T. Yates, Jr., University of Pittsburgh
Correspondent: Click to Email
Single walled carbon nanotubes are currently the subject of intensive studies because of their potential application as sorbents. This is due to the deep potential energy well for adsorption inside of the nanotube. To make accessible the interior of the nanotube O@sub 3@ was used as an oxidizer to attack the strained endcaps and also defect sites, causing local oxidation of carbon atoms there. The ozonolysis was followed by annealing in vacuum to decompose carbonyl functionalities formed during the ozone treatment. 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 O@sub 3@ at room temperature, followed by heating in vacuum to 873 K. It was found that at 133 K and 0.033 Torr, CF@sub 4@ adsorbs on closed SWNTs exhibiting its v@sub 3@ asymmetric stretching mode at 1267 cm@super -1@ (redshift = -15cm@super -1@). Adsorption on the nanotube exterior is accompanied by adsorption in the interior in the case of opened SWNTs. Internally-bound CF@sub 4@ exhibits its v@sub 3@ mode at 1247 cm@super -1@ (redshift = -35cm@super -1@). It was shown that at 133 K, Xe preferentially displaces internally-bound CF@sub 4@ species, and this counter-intuitive observation was confirmed by molecular simulations. The pseudo-one-dimensional confinement of CF@sub 4@ inside of (10,10) single walled carbon nanotubes does not result in the production of the splitting caused by transition dipole - transition dipole interaction which is observed in 3D ensembles of CF@sub 4@.