Atomic oxygen functionalization of double walled C nanotubes

The interaction of atomic oxygen with double walled C nanotubes at room temperature was studied by high resolution photoemission spectroscopy with synchrotron radiation. The nature of the chemical species formed on the nanotube sidewalls was followed from the initial adsorption up to advanced oxidation stages, whereas the thermal evolution of the O-related chemical species was monitored by fast photoemission. At the beginning of oxidation O atoms preferentially chemisorb forming C-O-C bonds, in ether and epoxy structures, which originate different components in the O1s spectra and exhibit different thermal stability. The onset of sp² lattice distortion is attested by the appearance of C-C bonds intermediate between sp² and sp³ configurations. The formation of double and triple C-O bonds is favored at later oxidation stages, and is accompanied by increasing lattice amorphization and decreasing emission in the Fermi level region. After annealing at 950 °C the O1s signal disappears and the presence of lattice defects emerges from the C1s line shape. This result, together with the chemical inertness of the deoxygenated nanotubes towards CO and O₂ adsorption suggests that the dangling bonds are promptly healed by thermal annealing and only stable topological defects are retained in the nanotube lattice.