X-ray photoelectron spectroscopic studies of surface modified single-walled carbon nanotube material

X-ray photoelectron spectroscopy (XPS) has been used to investigate the surface chemical state of two carbon nanotube materials and determine the evidence of surface modification from a reaction with dichlorocarbene. Carbon and oxygen were the major elements observed on the surface of the pristine carbon nanotube produced by electric arc discharge. After reaction with dichlorocarbene, chlorine atoms amounting to about 1.6 at.% were detected and the peak position of Cl 2p was at 201.3 eV, which can be attributed to existence of organic chlorocarbons. A new intense peak addition to the peak at 285 eV for the elemental sp2 and sp3 carbon atoms appears at the binding energy of about 287.5 eV in the C 1s narrow scan spectrum. This binding energy is typical for C 1s ionization of sp3 carbon in organic chlorocarbons. It was found that CC was the major carbon functional component in the surface modified carbon nanotube but other functional forms of carbon were also present such as CCl, CO, and OCO. With Ar+ ion sputtering, the atomic percent concentration of chlorine decreased by 65%, the carbon concentration increased significantly and the oxygen surface concentration decreased from 20.7 to 5.5 at.%. The surface chemical treatment with dichlorocarbene has thus modified the surface of the carbon nanotube with localization of small amounts of chlorine atoms on the carbon surface without disrupting the single walled nanotube bundles.