Ultrafast Dynamics of the First Excited-State of Quasi Monodispersed Single-Walled (9,7) Carbon Nanotubes

Time-resolved two color pump/probe spectroscopy was used to unravel the dynamics of ultrafast decay occurring upon population of the first optical bright excitonic level (E₁₁) in quasi-monodispersed, polymer-wrapped, single-walled (9,7)-carbon nanotubes (SWNTs) in toluene at room temperature. After resonant E₁₁ excitation, transfer of population to at least one optically dark level near E₁₁ was observed to take place within the first picosecond. In addition, phonon-assisted E₁₁-excitation led to transients similar to those observed upon resonant E₁₁-excitation indicating ultrafast vibrational relaxation convoluted with the temporal resolution of 60 fs

Separation of Single-Walled Carbon Nanotubes by 1‑Dodecanol-Mediated Size-Exclusion Chromatography

A simple, single-column, high-throughput fractionation procedure based on size-exclusion chromatography of aqueous sodium dodecyl sulfate suspensions of single-walled carbon nanotubes (SWCNTs) is presented. This procedure is found to yield monochiral or near monochiral SWCNT fractions of semiconducting SWCNTs. Unsorted and resulting monochiral suspensions are characterized using optical absorption and photoluminescence spectroscopy

Separation of Single-Walled Carbon Nanotubes with a Gel Permeation Chromatography System

A gel permeation chromatography system is used to separate aqueous sodium dodecyl sulfate suspensions of single-walled carbon nanotubes (SWCNTs). This automated procedure requires no precentrifugation, is scalable, and is found to yield monochiral SWCNT fractions of semiconducting SWCNTs with a purity of 61–95%. Unsorted and resulting monochiral fractions are characterized using optical absorption and photoluminescence spectroscopy

Length-Sorted, Large-Diameter, Polyfluorene-Wrapped Semiconducting Single-Walled Carbon Nanotubes for High-Density, Short-Channel Transistors

Samples of highly enriched semiconducting SWCNTs with average diameters of 1.35 nm have been prepared by combining PODOF polymer wrapping with size-exclusion chromatography. The purity of the material was determined to be >99.7% from the transfer characteristics of short-channel transistors comprising densely aligned sc-SWCNTs. The transistors have a hole mobility of up to 297 cm²V^–1 s^–1 and an On/Off ratio as high as 2 × 10⁸

Polymer Library Comprising Fluorene and Carbazole Homo- and Copolymers for Selective Single-Walled Carbon Nanotubes Extraction

To date, (<i>n</i>, <i>m</i>) single-walled carbon nanotubes (SWNTs) cannot be selectively synthesized. Therefore, postprocessing of SWNTs including solubilization and sorting is necessary for further applications. Toward this goal, we have synthesized a polymer library consisting of fluorene- and carbazole-based homo- and copolymers. Variations of the connection of these aromatics together with the incorporation of further conjugated monomers give access to a broad diversity of polymers. Their ability to selectively wrap specific (<i>n</i>, <i>m</i>) species is investigated toward HiPco SWNTs raw material which contains more than 40 (<i>n</i>, <i>m</i>) species. Absorption and fluorescence spectroscopies were used to analyze SWNTs/polymer suspensions. These results provide evidence for selective SWNTs/polymer interactions and allow a more detailed assessment of polymer structure–property relationships, thus paving the way toward custom synthesis of polymers for single (<i>n</i>, <i>m</i>) SWNTs extraction

Highly Selective Dispersion of Single-Walled Carbon Nanotubes via Polymer Wrapping: A Combinatorial Study via Modular Conjugation

Fourteen different “hairy-rod” conjugated polymers, 9,9-dioctylfluorene derivatives entailing 1,2,3-triazole, azomethine, ethynyle, biphenyle, stilbene, and azobenzene lateral units, are synthesized via modular conjugation and are systematically investigated with respect to their ability to selectively disperse SWCNTs. Four polymers of the azomethine type, with unprecedented selectivity toward dispersing (8,7), (7,6), and (9,5) SWCNT species, have been identified. In particular, azomethine polymers, herein applied for the first time for SWCNT dispersion, have been evidenced to be very effective in the highly selective solubilization of SWCNTs. The experimentally observed selectivity results are unambiguously supported by molecular dynamics simulations that account for the geometrical properties and deformation energy landscape of the polymer. Specifically, the calculations accurately and with high precision predict the experimentally observed selectivity for the (7,6) and (9,5) conformations

Sorting of Double-Walled Carbon Nanotubes According to Their Outer Wall Electronic Type <i>via</i> a Gel Permeation Method

In this work, we demonstrate the application of the gel permeation technique to the sorting of double-walled carbon nanotubes (DWCNTs) according to their outer wall electronic type. Our method uses Sephacryl S-200 gel and yields sorted fractions of DWCNTs with impurities removed and highly enriched in nanotubes with either metallic (M) or semiconducting (S) outer walls. The prepared fractions are fully characterized using optical absorption spectroscopy, transmission electron microscopy, and atomic force microscopy, and the entire procedure is monitored in real time using process Raman analysis. The sorted DWCNTs are then integrated into single nanotube field effect transistors, allowing detailed electronic measurement of the transconductance properties of the four unique inner@outer wall combinations of S@S, S@M, M@S, and M@M

Separation of Double-Walled Carbon Nanotubes by Size Exclusion Column Chromatography

In this report we demonstrate the separation of raw carbon nanotube material into fractions of double-walled (DWCNTs) and single-walled carbon nanotubes (SWCNTs). Our method utilizes size exclusion chromatography with Sephacryl gel S-200 and yielded two distinct fractions of single- and double-walled nanotubes with average diameters of 0.93 ± 0.03 and 1.64 ± 0.15 nm, respectively. The presented technique is easily scalable and offers an alternative to traditional density gradient ultracentrifugation methods. CNT fractions were characterized by atomic force microscopy and Raman and absorption spectroscopy as well as transmission electron microscopy