Control of p-doping on single-walled carbon nanotubes with nitronium hexafluoroantimonate in liquid phase

Abstract

We report that nitronium hexafluoroantimonate (NHFA) can be used as a strong p-type dopant on single-walled carbon nanotubes (SWCNTs). The diameter range of SWCNTs in this work ranged from 1.2 to 1.8 nm. The NHFA was dissolved in a mixed solution of tetramethylsilane/1,2-dichloroethane (1:1 by weight) with SWCNTs. The treated samples in liquid phase were characterized by UV-VIS-NIR absorption and Raman spectroscopies. We found that with increasing the NHFA concentration, the van Hove singularity-related transitions (ES11, ES22, and EM11) in the optical absorption spectra disappeared gradually and a new transition peak was clearly observed near 1.33 eV. G-band in the Raman spectra was upshifted to 1618 cm-1 from 1587 cm-1 of the pristine peak due to the phonon stiffening, an evidence of p-type doping. The sheet resistance of the SWCNT film was reduced up to 90%. After thermal annealing, the Raman spectra were recovered, similar to those of the pristine sample without any damage. ? 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.