Method for separating single-wall carbon nanotubes and compositions thereof

The invention relates to a process for sorting and separating a mixture of (n, m) type single-wall carbon nanotubes according to (n, m) type. A mixture of (n, m) type single-wall carbon nanotubes is suspended such that the single-wall carbon nanotubes are individually dispersed. The nanotube suspension can be done in a surfactant-water solution and the surfactant surrounding the nanotubes keeps the nanotube isolated and from aggregating with other nanotubes. The nanotube suspension is acidified to protonate a fraction of the nanotubes. An electric field is applied and the protonated nanotubes migrate in the electric fields at different rates dependent on their (n, m) type. Fractions of nanotubes are collected at different fractionation times. The process of protonation, applying an electric field, and fractionation is repeated at increasingly higher pH to separated the (n, m) nanotube mixture into individual (n, m) nanotube fractions. The separation enables new electronic devices requiring selected (n, m) nanotube types

Preferred orientation in fibers of HiPco single wall carbon nanotubes from diffuse x-ray scattering

Neat Fibers of HiPco single wall carbon nanotubes extruded from strong acid suspensions exhibit preferred orientation along fiber axes. We characterize the extrusion-induced alignment using x-ray fiber diagrams and polarized Raman scattering, using a model which allows for some fraction of the sample to remain completely unaligned. We show that both x-ray and Raman data are required for a complete texture analysis of SWNT fibers

Thermoelectric Power of p-Doped Single-Wall Carbon Nanotubes and the Role of Phonon Drag

We measured thermoelectric power S of bulk single-wall carbon nanotube (SWNT) materials p-doped with acids. In contrast to oxygen-exposed or degassed samples, S is very small at the lowest temperatures, increases super-linearly above a characteristic and sample-dependent T, and then levels off. We attribute this unusual behavior to 1-D phonon drag, in which the depression of the Fermi energy cuts off electron-phonon scattering at temperatures below a characteristic T0. This idea is supported by a model calculation in which the low temperature behavior of phonon drag is specifically related to the one-dimensional character of the electronic spectrum

Single Wall Carbon Nanotube Fibers Extruded from Super-Acid Suspensions: Preferred Orientation, Electrical and Thermal Transport

Fibers of single wall carbon nanotubes extruded from super-acid suspensions exhibit preferred orientation along their axes. We characterize the alignment by x-ray fiber diagrams and polarized Raman scattering, using a model which allows for a completely unaligned fraction. This fraction ranges from 0.17 to 0.05±0.02 for three fibers extruded under different conditions, with corresponding Gaussian full widths at half-maximum (FWHM) from 64o to 44o±2o. FWHM, aligned fraction, electrical and thermal transport all improve with decreasing extrusion orifice diameter. Resistivity, thermoelectric power and resonant-enhanced Raman scattering indicate that the neat fibers are strongly p-doped; the lowest observed ρ is 0.25mΩcm at 300 K. High temperature annealing increases ρ by more than 1 order of magnitude and restores the Raman resonance associated with low-energy van Hove transitions, without affecting the nanotube alignment

Macroscopic Neat Single-Walled Carbon Nanotubes Fibers

The first-ever well-aligned continuous macroscopic neat single-walled carbon nanotube (SWNT) fibers were produced using conventional spinning techniques. Neat SWNT fibers, containing no surfactant or polymer, were made by spinning dispersions of SWNTs in 102% sulfuric acid into different coagulants. The critical role of sulfuric acid in dispersing and aligning SWNTs during fiber formation has been explored. Characterization shows alignment greater than any other macroscopic neat SWNT material reported to-date while providing insight into the fundamental hierarchy and nature of SWNT fiber formation. Electrical, thermal, and mechanical measurements indicate that neat SWNT fibers hold tremendous potential for future applications

Synthesis and structure of oxygen-deficient La2NiCoO5 and LaSrCo2O5 phases

The La2NiCoO5 and LaSrCo2O5 phases have been synthesized by the temperature-programmed reduction (TPR) of the parent mixed perovskites LaNi0.5Co0.5O3 and La0.5Sr0.5CoO3, respectively, under an ammonia atmosphere. While La2NiCoO5 adopts a structure similar to the vacancy-ordered La2Ni2O5, LaSrCo2O5 crystallized in a brownmillerite-like structure. The reactivity of the perovskite oxides towards reduction by ammonia and the structure of the product oxides are found to be guided by factors such as the coordination and oxidation state of the transition-metal cations

Tritium sequence analysis of oligoribonucleotides: a combination of post-labeling and thin-layer chromatographic techniques for the analysis of partial snake venom phosphodiesterase digests

A tritium derivative method for sequence analysis of polyribonucleotides is detailed, which is based on borotritide reduction of oligonucleotide-3′ dialdehydes generated by controlled snake venom phosphodiesterase/alkaline phosphomonoesterase digestion and periodate treatment of time point aliquots of the incubation mixture. Radioactive oligonucleotide derivatives are resolved according to chain length by PEI-cellulose(1) anion-exchange TLC and their 3′-termini identified by techniques described in the preceding paper of this series(2). The present tritium derivative method is compared with the one described previously(2)