title: Molecular-crowding-induced clustering of DNA-wrapped carbon nanotubes for facile length fractionation.
abstract: Emerging applications require single-wall carbon nanotubes (SWCNTs) of well-defined length. Yet the use of length-defined SWCNTs is limited, in part due to the lack of an easily accessible materials preparation method. Here, we present a new strategy for SWCNT length fractionation based on molecular crowding induced cluster formation. We show that the addition of polyethylene glycol (PEG) as a crowding agent into DNA-wrapped SWCNT dispersion leads to the formation of reversible, nematic, and rodlike microclusters, which can be collected by gentle centrifugation. Since shorter SWCNTs form clusters at higher polyethylene glycol concentration, gradual increase in PEG concentration results in length fractionated SWCNTs. Using atomic force microscopy (AFM) we show that fractions with average lengths of 60-500 nm and standard deviations of 30-40% can be obtained. The concept of molecular-crowding-based fractionation should be applicable to other nanoparticle dispersions.
authors: Polymers Division,  National Institute of Standards in Technology , 100 Bureau Drive, Gaithersburg, Maryland 20899-8542, United States.
authors: Constantine Y
authors: CY
authors: Khripin
authors: Nicholas
authors: N
authors: Arnold-Medabalimi
authors: Ming
authors: M
authors: Zheng
mesh_terms: D000042:Absorption; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D004247:DNA / Q000737:chemistry*; D004271:DNA, Fungal / Q000737:chemistry; D004735:Energy Transfer; D008970:Molecular Weight; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D055620:Optical Phenomena; D011092:Polyethylene Glycols / Q000737:chemistry; D012441:Saccharomyces cerevisiae
chemical_list: D004271:DNA, Fungal; D037742:Nanotubes, Carbon; D009838:Oligodeoxyribonucleotides; D011092:Polyethylene Glycols; D004247:DNA