title: Selective removal of metallic single-walled carbon nanotubes with small diameters by using nitric and sulfuric acids.
abstract: Coexistence of metallic and semiconducting carbon nanotubes has often been a bottleneck in many applications and much fundamental research. Single-walled carbon nanotubes (SWCNTs) were dissolved in HNO3/H2SO4 mixture to confirm differing reactivity between metallic (m) and semiconducting (s) SWCNTs. With HNO3/H2SO4 treatment, s-SWCNTs remained intact, while m-SWCNTs were completely removed for SWCNTs with small diameters less than 1.1 nm, which was confirmed by resonant Raman and optical absorption spectra. We also showed that nitronium ions (NO2+) dissolved in the HNO3/H2SO4 solution could preferably attack the m-SWCNTs, which was supported by our theoretical calculation. This clear selectivity can be explained by the preferential adsorption of positively charged NO2+ on m-SWCNTs due to more available electron densities at the Fermi level in the m-SWCNTs. We report for the first time a selective removal of small-diameter m-SWCNTs by using HNO3/H2SO4 solution, which presented a striking contrast to the diameter-selective removal of SWCNTs by oxidative etching reported previously.
authors.affiliation: BK21 Physics Division, Institute of Basic Science, Center for Nanotubes and Nanostructured Composites, Sungkyunkwan University, Suwon 440-746, Republic of Korea.
authors.forename: Cheol-Min
authors.initials: CM
authors.lastname: Yang
authors.forename: Jin Sung
authors.initials: JS
authors.lastname: Park
authors.forename: Kay Hyeok
authors.initials: KH
authors.lastname: An
authors.forename: Seong Chu
authors.initials: SC
authors.lastname: Lim
authors.forename: Kwanyong
authors.initials: K
authors.lastname: Seo
authors.forename: Bongsoo
authors.initials: B
authors.lastname: Kim
authors.forename: Kyung Ah
authors.initials: KA
authors.lastname: Park
authors.forename: Seungwu
authors.initials: S
authors.lastname: Han
authors.forename: Chong Yun
authors.initials: CY
authors.lastname: Park
authors.forename: Young Hee
authors.initials: YH
authors.lastname: Lee