A carbon nanotube composition capable of producing an FET having improved mobility is provided. The carbon nanotube composition of the present invention is a halogen-free carbon nanotube composition comprising a carbon nanotube having the following features (1) and (2).

(1) A dispersion liquid obtained by dispersing the carbon nanotube in a solution containing a cholic acid derivative and water has, in the absorption spectrum in the wavelength range of 300 nm to 1100 nm measured by an ultraviolet/visible/near-infrared spectroscopy, the minimum absorbance in the range of 600 nm to 700 nm and the maximum absorbance in the range of 900 nm to 1050 nm; wherein the ratio of the minimum absorbance and the maximum absorbance is 2.5 or more and 4.5 or less; and
(2) the dispersion liquid has the height ratio of the G-band and the D-band (value of (D/G)×100) of 3.33 or less, as measured by a Raman spectrophotometer, using light having a wavelength of 532 nm as excitation light.

A method for producing a carbon nanotube-metal composite in which carbon nanotubes are layered on a metal substrate, the method comprising: (i) depositing a liquid, in which carbon nanotubes are suspended, onto said metal substrate; (ii) during or after step (i), subjecting said liquid to a shearing force sufficient to spatially confine the liquid to induce at least partial alignment of said carbon nanotubes on said metal substrate; and (iii) removing said liquid to produce said carbon nanotube-metal composite; wherein, after step (iii), the lengthwise dimensions of said carbon nanotubes are adhered to and oriented parallel with said metal surface, and said carbon nanotubes are at least partially aligned with each other. In some embodiments, the liquid is deposited in the form of droplets, and the droplets are subjected to a shearing force to cause them to elongate, which induces at least partial alignment of the carbon nanotubes.

A method for producing a carbon nanotube-metal composite in which carbon nanotubes are layered on a metal substrate, the method comprising: (i) depositing a liquid, in which carbon nanotubes are suspended, onto said metal substrate; (ii) during or after step (i), subjecting said liquid to a shearing force sufficient to spatially confine the liquid to induce at least partial alignment of said carbon nanotubes on said metal substrate; and (iii) removing said liquid to produce said carbon nanotube-metal composite; wherein, after step (iii), the lengthwise dimensions of said carbon nanotubes are adhered to and oriented parallel with said metal surface, and said carbon nanotubes are at least partially aligned with each other. In some embodiments, the liquid is deposited in the form of droplets, and the droplets are subjected to a shearing force to cause them to elongate, which induces at least partial alignment of the carbon nanotubes.

A method for carbon nanotube purification, preferably including: providing carbon nanotubes; depositing a mask; and/or selectively removing a portion of the mask; and optionally including removing a subset of the carbon nanotubes and/or removing the remaining mask.

A method for carbon nanotube purification, preferably including: providing carbon nanotubes; depositing a mask; and/or selectively removing a portion of the mask; and optionally including removing a subset of the carbon nanotubes and/or removing the remaining mask.

The disclosed method includes a separation step wherein composite particles are transferred to a vicinity of an inlet of a fibrous carbon nanostructure path configured to recover fibrous carbon nanostructures by allowing the fibrous carbon nanostructures to pass therethrough, and a fluid flowing toward the inlet of the path and an external force including a component of a direction opposite to the direction in which the fluid flows are applied to the composite particles to separate the fibrous carbon nanostructures and a particulate ceramic support substrate; and a recovery step wherein the separated fibrous carbon nanostructures are transferred to an interior of the path for recovery by a flow of the fluid, with the separated substrate transferred away from the fibrous carbon nanostructure path for recovery, wherein, in the separation step, the external force applied to the substrate is greater than that applied to the fibrous carbon nanostructures.

The disclosed method includes a separation step wherein composite particles are transferred to a vicinity of an inlet of a fibrous carbon nanostructure path configured to recover fibrous carbon nanostructures by allowing the fibrous carbon nanostructures to pass therethrough, and a fluid flowing toward the inlet of the path and an external force including a component of a direction opposite to the direction in which the fluid flows are applied to the composite particles to separate the fibrous carbon nanostructures and a particulate ceramic support substrate; and a recovery step wherein the separated fibrous carbon nanostructures are transferred to an interior of the path for recovery by a flow of the fluid, with the separated substrate transferred away from the fibrous carbon nanostructure path for recovery, wherein, in the separation step, the external force applied to the substrate is greater than that applied to the fibrous carbon nanostructures.

To reduce cost for the method for separating semiconducting carbon nanotube from a mixture of metallic and semiconducting carbon nanotubes. The separation method includes preparing a dispersion by mixing a first substance, a second substance, SDS, SC, and a mixture of metallic and semiconducting carbon nanotubes with a solvent, wherein the dispersion into two layers, which are a first layer mainly containing the first substance and a second layer mainly containing the second substance, whereby the semiconducting carbon nanotube is transferred into the first layer, and the metallic carbon nanotube is transferred into the second layer, wherein the first substance is an α-glucan which is composed of glucose linked via α-glucosidic linkage and which has a weight average molecular weight Mw of 4,000 to 7,000 and has a ratio in amount of α-1, 6 linked glucose residues to the entire glucose residues of 40 to 70%.

To reduce cost for the method for separating semiconducting carbon nanotube from a mixture of metallic and semiconducting carbon nanotubes. The separation method includes preparing a dispersion by mixing a first substance, a second substance, SDS, SC, and a mixture of metallic and semiconducting carbon nanotubes with a solvent, wherein the dispersion into two layers, which are a first layer mainly containing the first substance and a second layer mainly containing the second substance, whereby the semiconducting carbon nanotube is transferred into the first layer, and the metallic carbon nanotube is transferred into the second layer, wherein the first substance is an α-glucan which is composed of glucose linked via α-glucosidic linkage and which has a weight average molecular weight Mw of 4,000 to 7,000 and has a ratio in amount of α-1, 6 linked glucose residues to the entire glucose residues of 40 to 70%.

Disclosed are methods for separating carbon nanotubes on the basis of a specified parameter, such as length. The methods include labelling of the carbon nanotubes with a biological moiety, followed by SDS-PAGE and staining, to separate the carbon nanotubes on the basis of length and/or characterize their length. In some embodiments, egg-white lysozyme, conjugated covalently onto single-walled carbon nanotubes surfaces using carbodiimide method, followed by SDS-PAGE and visualization of the single-walled nanotubes using silver staining, provides high resolution characterization of length of the single-walled carbon nanotubes. This high precision, inexpensive, rapid and simple separation method obviates the need for centrifugation, additional chemical analyses, and expensive spectroscopic techniques such as Raman spectroscopy to visualize carbon nanotube bands. The disclosed methods find utility in quality-control in the manufacture of carbon nanotubes of specific lengths.