Single-walled carbon nanotubes filled with nickel halogenides: Atomic structure and doping effect

NiX2@SWCNT (X?=?Cl, Br) nanostructures were prepared by capillary filling of single-walled carbon nanotube channels with nickel halogenide melts with slow cooling down to room temperature for better crystallization. The HRTEM data indicated formation of well-ordered 1D NiBr2 crystals, with the experimental atomic structure representing a fragment of the bulk structure. The lattice constant coincides with the corresponding distance in bulk lattice. The 1D crystal structure was modeled using DFT within the PW-GGA approach. According to the Raman, X-ray photoelectron, X-ray and optical absorption spectroscopic data and the DFT results obtained within the rigid band model, nickel halogenides display acceptor behavior with the corresponding charge transfer from the single-walled carbon nanotube walls to the NiX2 nanocrystals. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim