title: Capillary electrophoresis of covalently functionalized single-chirality carbon nanotubes.
abstract: We demonstrate the separation of chirality-enriched single-walled carbon nanotubes (SWCNTs) by degree of surface functionalization using high-performance CE. Controlled amounts of negatively charged and positively charged functional groups were attached to the sidewall of chirality-enriched SWCNTs through covalent functionalization using 4-carboxybenzenediazonium tetrafluoroborate or 4-diazo-N,N-diethylaniline tetrafluoroborate, respectively. Surfactant- and pH-dependent studies confirmed that under conditions that minimized ionic screening effects, separation of these functionalized SWCNTs was strongly dependent on the surface charge density introduced through covalent surface chemistry. For both heterogeneous mixtures and single-chirality-enriched samples, covalently functionalized SWCNTs showed substantially increased peak width in electropherogram spectra compared to nonfunctionalized SWCNTs, which can be attributed to a distribution of surface charges along the functionalized nanotubes. Successful separation of functionalized single-chirality SWCNTs by functional density was confirmed with UV-Vis-NIR absorption and Raman scattering spectroscopies of fraction collected samples. These results suggest a high degree of structural heterogeneity in covalently functionalized SWCNTs, even for chirality-enriched samples, and show the feasibility of applying CE for high-performance separation of nanomaterials based on differences in surface functional density.
authors.affiliation: State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing, P. R. China.|Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
authors.forename: Pingli
authors.initials: P
authors.lastname: He
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
authors.forename: Brendan
authors.initials: B
authors.lastname: Meany
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Piao
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.
authors.forename: Hyejin
authors.initials: H
authors.lastname: Kwon
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.|Department of Chemistry, Xiamen University, Xiamen, P. R. China.
authors.forename: Shunliu
authors.initials: S
authors.lastname: Deng
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA.|Maryland NanoCenter, University of Maryland, College Park, MD, USA.
authors.forename: YuHuang
authors.initials: Y
authors.lastname: Wang
mesh_terms: D019075:Electrophoresis, Capillary / Q000379:methods*; D037742:Nanotubes, Carbon / Q000032:analysis / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013237:Stereoisomerism; D013501:Surface-Active Agents
chemical_list: D037742:Nanotubes, Carbon; D013501:Surface-Active Agents
keywords: Capillary electrophoresis; Functionalization; Separation; Single chirality; Single-walled carbon nanotubes