title: Electron paramagnetic resonance investigation of purified catalyst-free single-walled carbon nanotubes.
abstract: Electron paramagnetic resonance of single-walled carbon nanotubes (SWCNTs) has been bedevilled by the presence of paramagnetic impurities. To address this, SWCNTs produced by laser ablation with a nonmagnetic PtRhRe catalyst were purified through a multiple step centrifugation process in order to remove amorphous carbon and catalyst impurities. Centrifugation of a SWCNT solution resulted in sedimentation of carbon nanotube bundles containing clusters of catalyst particles, while isolated nanotubes with reduced catalyst particle content remained in the supernatant. Further ultracentrifugation resulted in highly purified SWCNT samples with a narrow diameter distribution and almost no detectable catalyst particles. Electron paramagnetic resonance (EPR) signals were detected only for samples which contained catalyst particles, with the ultracentrifuged SWCNTs showing no EPR signal at X-band (9.4 GHz) and fields < 0.4 T.
authors.affiliation: Department of Materials, University of Oxford, Parks Rd, Oxford, OX1 3PH, United Kingdom.
authors.forename: Mujtaba
authors.initials: M
authors.lastname: Zaka
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ito
authors.forename: Huiliang
authors.initials: H
authors.lastname: Wang
authors.forename: Wenjing
authors.initials: W
authors.lastname: Yan
authors.forename: Alex
authors.initials: A
authors.lastname: Robertson
authors.forename: Yimin A
authors.initials: YA
authors.lastname: Wu
authors.forename: Mark H
authors.initials: MH
authors.lastname: Rümmeli
authors.forename: David
authors.initials: D
authors.lastname: Staunton
authors.forename: Takeshi
authors.initials: T
authors.lastname: Hashimoto
authors.forename: John J L
authors.initials: JJ
authors.lastname: Morton
authors.forename: Arzhang
authors.initials: A
authors.lastname: Ardavan
authors.forename: G Andrew D
authors.initials: GA
authors.lastname: Briggs
authors.forename: Jamie H
authors.initials: JH
authors.lastname: Warner
mesh_terms: D000042:Absorption; D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006108:Graphite / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008280:Magnetics; D037742:Nanotubes, Carbon / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013696:Temperature; D013997:Time Factors; D014461:Ultracentrifugation; D014732:Vibration; D014835:Volatilization
chemical_list: D037742:Nanotubes, Carbon; D006108:Graphite; D007501:Iron