Tuning the Electronic Properties of Single-Walled Carbon Nanotubes by Filling with Electron Donor and Acceptor Compounds

The endohedral chemical functionalization of single-walled carbon nanotubes (SWCNTs) allows for tuning their electronic properties toward applications. It was demonstrated that SWCNTs can be filled with elementary substances, chemical compounds and molecules. In this work, we performed the filling of SWCNTs with metal halogenide (cobalt iodide, CoI2) and metal carbide (nickel carbide, Ni3C). The filling of SWCNTs with CoI2 was conducted by the melt method. The filling of SWCNTs with Ni3C was performed by the thermal treatment of nickelocene-filled nanotubes. The filled SWCNTs were investigated by the high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The HRTEM data prove the encapsulation of compounds inside the SWCNTs. By combining the Raman spectroscopy and XPS data, it was shown that the encapsulated CoI2 causes p-doping of nanotubes accompanied by the downshift of the Fermi level of nanotubes. The embedded Ni3C leads to n-doping of SWCNTs with upshifting of the Fermi level of nanotubes. The obtained results allow for applying filled SWCNTs in arange of fields such as nanoelectronics, energy storage, sensors, catalysis and biomedicine.