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

Abstract

AbstractWe 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 (${\rm E}_{11}^{\rm S}$, ${\rm E}_{22}^{\rm S}$, and ${\rm E}_{11}^{\rm M}$) 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.