Highly Selective Dispersion of Carbon Nanotubes by Using Poly(phenyleneethynylene)-Guided Supermolecular Assembly (original) (raw)
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ACS Nano, 2014
Recently, several important advances in techniques for the separation of single-walled carbon nanotubes (SWNTs) by chiral index have been developed. These new methods allow for the separation of SWNTs through selective adsorption and desorption of different (n,m) chiral indices to and from a specific hydrogel. Our group has previously developed a kinetic model for the chiral elution order of separation; however, the underlying mechanism that allows for this separation remains unknown. In this work, we develop a quantitative theory that provides the first mechanistic insights for the separation order and binding kinetics of each SWNT chirality (n,m) based on the surfactant-induced, linear charge density, which we find ranges from 0.41 e À /nm for (7,3) SWNTs in 17 mM sodium dodecyl sulfate (SDS) to 3.32 e À /nm for (6,5) SWNTs in 105 mM SDS. Adsorption onto the hydrogel support is balanced by short-distance hard-surface and long-distance electrostatic repulsive SWNT/substrate forces, the latter of which we postulate is strongly dependent on surfactant concentration and ultimately leads to gel-based single-chirality semiconducting SWNT separation. These molecular-scale properties are derived using bulk-phase, forward adsorption rate constants for each SWNT chirality in accordance with our previously published model. The theory developed here quantitatively describes the experimental elution profiles of 15 unique SWNT chiralities as a function of anionic surfactant concentration between 17 and 105 mM, as well as phenomenological observations of the impact of varying preparatory conditions such as extent of ultrasonication and ultracentrifugation. We find that SWNT elution order and separation efficiency are primarily driven by the morphological change of SDS surfactant wrapping on the surface of the nanotube, mediated by SWNT chirality and the ionic strength of the surrounding medium. This work provides a foundational understanding for high-purity, preparative-scale separation of as-produced SWNT mixtures into isolated, single-chirality fractions.
Controlled synthesis of single-chirality carbon nanotubes
Nature, 2014
Over the last two decades, single-walled carbon nanotubes (SWCNTs) have received much attention because their extraordinary properties are promising for numerous applications 1,2. Many of these properties depend sensitively on SWCNT structure, which is characterized by the chiral index (n,m) that denotes the length and orientation of the circumferential vector in the hexagonal carbon lattice. Electronic properties are particularly strongly affected, with subtle structural changes switching tubes from metallic to semiconducting with various bandgaps. Monodisperse 'single-chirality' (that is, with a single (n,m) value) SWCNTs are thus needed to fully exploit their technological potential 1,2. Controlled synthesis through catalyst engineering 3-6 , end-cap engineering 7 or cloning strategies 8,9 and also tube sorting based on chromatography 10,11 , density-gradient centrifugation, electrophoresis and other techniques 12 have delivered SWCNT samples with narrow distributions of tube diameter and enriched in a particular tube type. But an effective pathway to truly monodisperse SWCNTs remains elusive. The use of template molecules to unambiguously dictate the diameter and chirality of the resulting nanotube 8,13-16 holds great promise in this regard, but has hitherto had only limited practical success 7,17,18. Here we show that this bottom-up strategy can produce targeted nanotubes: we convert molecular precursors into ultrashort singly capped (6,6) 'armchair' nanotube seeds using surface-catalysed cyclodehydrogenation on a Pt(111) surface, and then elongate these during a subsequent growth phase to produce single-chirality and essentially defect-free SWCNTs with lengths up to a few hundred nanometres. We expect that our onsurface synthesis approach will provide a route to nanotube-based materials with highly
Macromolecules, 2004
Because of outstanding electrical conductivity, thermal conductivity, and mechanical strength, single-wall carbon nanotubes (SWNT) have enormous potential in field emission displays, supercapacitors, molecular computers, and ultrahigh-strength materials. 1,2 For optimal performance in most applications, the SWNT should be separated into individual tubes or bundles of only a few tubes. However, the as-prepared SWNT contain impurities of metal catalyst particles and amorphous carbon, and because of strong van der Waals attraction, the SWNT pack into bundles that aggregate into tangled networks. Dissolution of SWNT in water, which is important because of potential biomedical applications and biophysical processing schemes, has been facilitated by surfactants and polymers and by chemical modification. 3-11 Here we report a method by which pristine SWNT are solubilized, separated from catalyst particles, and separated from excess dispersant to produce SWNT with grafted poly(sodium 4-styrenesulfonate) (PSS) as an aqueous solution that is stable indefinitely. The method is illustrated in Scheme 1.
Supramolecular aggregation of functionalized carbon nanotubes
Chemical Communications, 2009
All reagents and solvents were obtained from commercial suppliers and used without further purification. MWNT 7000 series and very thin-MWNT were purcharsed from Nanocyl. SWNT were purchased from Carbon Nanotechnologies, Inc. (HiPCOSWNT, CarbonNanotechnology,Inc.,lot#R0496,www.cnanotech.com). Characterization techniques. Thermogravimetric analyses of 1mg of each compound were recorded on a TGA Q500 (TA Instruments) under N 2 , by equilibrating at 100 °C, and following a ramp of 10 °C/min up to 900 °C. TEM analyses were performed on a TEM Philips EM208, using an accelerating voltage of 100 kV. 0.1 mg of the different compounds were dispersed in 1 mL of solvent and one drop of this solution was deposited on a TEM grid (200 mesh, Nichel, carbon only). For TEM characterization, Philips EM 208, accelerating voltage of 100 kV was used. Raman spectra were recorded with an inVia Renishaw microspectrometer equipped with a He-Ne laser at 633nm. Synthesis of SWNT-1 and MWNT-2. (Scheme 1) An excess of aminoacid and paraformaldehide were added to a suspension of 20 mg of pristine SWNT or MWNT in 50mL of DMF. The reaction mixture was heated at 130 ºC for 5 days, reagents where added every day. Compounds were filtered with a Millipore system (JH 0.45 µm filter), the solid was washed thoroughly with methanol until the solvent was clear. For TGA and Raman characterization, the precipitated was dried under vacuum overnight. To cleave the Boc group from functionalized SWNT and MWNT, they were dispersed by sonication in 15 mL of DMF, respectively. After that, HCl gas was bubbled for 5 min. Solutions were kept overnight under magnetic stirred. Solutions were filtrated and washed thoroughly with methanol. The precipitates were dried
Biomolecules
Carbon nanotubes (CNT) have fascinating applications in flexible electronics, biosensors, and energy storage devices, and are classified as metallic or semiconducting based on their chirality. Semiconducting CNTs have been teased as a new material for building blocks in electronic devices, owing to their band gap resembling silicon. However, CNTs must be sorted into metallic and semiconducting for such applications. Formerly, gel chromatography, ultracentrifugation, size exclusion chromatography, and phage display libraries were utilized for sorting CNTs. Nevertheless, these techniques are either expensive or have poor efficiency. In this study, we utilize a novel technique of using a library of nine tripeptides with glycine as a central residue to study the effect of flanking residues for large-scale separation of CNTs. Through molecular dynamics, we found that the tripeptide combinations with threonine as one of the flanking residues have a high affinity for metallic CNTs, whereas...