Acceptor doping of single-walled carbon nanotubes by encapsulation of zinc halogenides

To modify the electronic properties of single-walled carbon nanotubes (SWCNTs), ZnX2@SWCNT (X = Cl, Br, I) nanostructures were prepared by capillary filling of 1.4-1.6 nm single-walled carbon nanotubes (SWCNT) with zinc halogenide melts. The loading factor is estimated as 30% for ZnCl2 and approximately 60% for ZnBr2 and ZnI2. Well-ordered 1D crystals were observed by TEM only for ZnI2@SWCNT. We propose two possible atomic structures of the 1D crystals, (Zn4I7)(n) and less stable (Zn4I9)(n). According to the optical absorption and photoemission data, there is a charge transfer from the nanotube to the filler for all ZnX2@SWCNT nanostructures. The results of the DFT PW-GGA modeling indicate that the acceptor properties correspond to (Zn4I9)(n) only.