Synthesis of covalently attached hexadecaanilines on carbon nanotubes : toward electronic nanocarbon preparation

We describe the direct covalent-grafting synthesis of well-defined aniline oligomers, such as tetraaniline (A4) and hexadecaaniline (A16, major)/eicosaaniline (A20, minor), on the sidewalls of carbon nanotubes (CNTs), via dediazonization reaction, for achieving highly soluble nanomaterials suitable for printing purposes, with long-term physical stability. Chemically grafting a layer of electroactive hexadecaanilines on CNTs resembles semiconductive encapsulation of functionalized CNTs. The resulting covalent nanoconjugates SWNT–(A4)x, MWNT–(A4)x, SWNT–(A16/20)x, and MWNT–(A16/20)x were characterized by various spectroscopic and microscopic mapping methods. The combination of transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS) analyses provided direct evidence for A16/20 attachment to the CNTs, giving confirmation of the presence of heteroatoms surrounding the CNTs that was absent in the parent CNTs. Subsequent atom mapping in the vicinity of the tube structure allowed us to illustrate the 3D distribution of heteroatoms along the CNT surface.