# US 11,440,800 B2 · Method for separating and recovering carbon nanotubes

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- Number: US 11,440,800 B2
- Document ID: US11440800B2
- Status: Granted
- Kind: B2
- Application number: 17/254,689
- Filed: 2019-07-25
- Published: 2021-09-02
- Granted: 2022-09-13
- Earliest claimed: 2018-07-27
- Assignees: National Institute of Advanced Industrial Science and Technology
- Applicants: National Institute of Advanced Industrial Science and Technology
- Inventors: Takeshi Tanaka; Yohei Yomogida; Hiromichi Kataura
- Web page: https://patentgrep.com/patent/US11440800B2

## CPC

- C01B 32/172: Sorting
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- C01B 2202/02: Single-walled nanotubes
- C01B 2202/20: Nanotubes characterized by their properties
- C01B 2202/22: Electronic properties
- C01B 2202/26: Mechanical properties
- C01B 2202/36: Diameter
- C01P 2002/84: by UV- or VIS- data
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

The invention has for its object to provide an aqueous solution for structural separation capable of acting on carbon nanotubes (CNTs) having a specific structure thereby separating them with high accuracy, a separation and recovery method capable of allowing the aqueous solution to act on CNTs having a specific structure thereby separating and recovering them, and CNTs obtained by the separation and recovery method. According to the invention, it is possible to separate CNTs having a specific structure with high accuracy by solubilizing lithocholic acid or a lithocolic acid isomer that has high hydrophobicity and is insoluble in water by itself, and a carbon nanotube obtained by using an aqueous solution containing lithocholic acid or a lithocholic acid isomer, each solubilized, as an aqueous solution for structural separation of CNTs.

## Claims

### Claim 1

A method for separating and recovering carbon nanotubes, comprising;
eluting carbon nanotubes having a diameter of 1 nm or less from a gel on which carbon nanotubes are adsorbed, by using an aqueous solution containing at least one selected from the group consisting of solubilized lithocholic acid and solubilized lithocholic acid isomer.

### Claim 2 (depends on 1)

A method for separation and recovery of carbon nanotubes as recited in claim 1, wherein said lithocholic acid, and said lithocholic acid isomer are solubilized by another surfactant.

### Claim 3 (depends on 2)

A method for separation and recovery of carbon nanotubes as recited in claim 2, wherein said another surfactant is sodium dodecyl sulfate and/or sodium cholate.

### Claim 4 (depends on 1)

A method for separation and recovery of carbon nanotubes as recited in claim 1, further comprising, after eluting carbon nanotubes having a diameter of 1 nm or less, eluting carbon nanotubes remaining in the gel with a diameter of larger than 1 nm.

### Claim 5 (depends on 1)

A method for separation and recovery of carbon nanotubes as recited in claim 1, wherein said lithocholic acid and said lithocholic acid isomer are solubilized by another surfactant.

### Claim 6 (depends on 5)

A method for separation and recovery of carbon nanotubes as recited in claim 5, wherein said another surfactant is sodium dodecyl sulfate and/or sodium cholate.

### Claim 7 (depends on 1)

A method for separating and recovering carbon nanotubes as recited in claim 1, wherein the carbon nanotubes with a different chiral index are selectively eluted from the gel on which the carbon nanotubes are adsorbed.

### Claim 8 (depends on 7)

A method for separation and recovery of carbon nanotubes as recited in claim 7, wherein said lithocholic acid and said lithocholic acid isomer are solubilized by another surfactant.

### Claim 9 (depends on 8)

A method for separation and recovery of carbon nanotubes as recited in claim 8, wherein said another surfactant is sodium dodecyl sulfate and/or sodium cholate.

### Claim 10 (depends on 1)

A method for separation and recovery of carbon nanotubes as recited in claim 1, wherein the aqueous solution containing the at least one selected from the group consisting of solubilized lithocholic acid and solubilized lithocholic acid isomer is prepared to obtain an aqueous solution for separation; preparing the gel containing carbon nanotubes; mixing the gel and the aqueous solution for separation to elute the carbon nanotubes; and separating the carbon nanotubes.