Separation of single-walled carbon nanotubes by self-forming density gradient ultracentrifugation

1. A method of using a density gradient to separate single-walled carbon nanotubes, said method comprising:

providing a nanotube composition comprising at least one surface active block copolymer and a mixture of single-walled carbon nanotubes, said mixture selected from mixed nanotube diameters, mixed nanotube chiralities, mixed nanotube electronic types and combinations of said mixtures;

contacting said nanotube composition with a fluid medium capable of forming a density gradient therein under centrifugation, and centrifuging said nanotube composition; and

separating said nanotube composition into at least one separation fraction enriched with single-walled carbon nanotubes of at least one of said selected nanotube diameter, nanotube chirality and nanotube electronic type, said single-walled carbon nanotubes complexed with a said surface active block copolymer, said enrichment relative to said nanotube composition,

said method without pre-centrifugation preparation of a linear density gradient.

2. The method of claim 1 comprising isolating at least one of said at least one separation fraction from said fluid medium.

3. The method of claim 2 comprising repeating said providing, contacting, centrifuging, separating and isolating, with at least one said isolated separation fraction.

4. The method of claim 3 wherein said repeating comprises changing from at least one of a preceding said surface active block copolymer and said fluid medium.

5. The method of claim 2 comprising removal of at least one said surface active block copolymer from said single-walled carbon nanotubes, in at least one said isolated separation fraction.

6. The method of claim 2 wherein a said surface active block copolymer is selected from linear and X-shaped amphiphilic poly(alkylene oxide) block copolymers and combinations thereof.

7. The method of claim 6 wherein a said linear amphiphilic block copolymer comprises poly(ethylene oxide) blocks and poly(propylene oxide) blocks.

8. The method of claim 7 wherein one said isolated separation fraction is enriched with semiconducting single-walled carbon nanotubes.

9. The method of claim 6 wherein an X-shaped amphiphilic block copolymer comprises poly(ethylene oxide) and poly(polypropylene oxide) blocks.

10. The method of claim 9 wherein one said isolated separation fraction is enriched with metallic single-walled carbon nanotubes.

11. The method of claim 1 wherein said fluid medium comprises aqueous iodixanol.

12. The method of claim 11 wherein a fraction of said centrifuged nanotube composition is isopycnic at a position along said formed density gradient.

13. A method of using a surface active block copolymer to separate single-walled carbon nanotubes, said method comprising:

providing a fluid medium capable of forming a density gradient therein under centrifugation;

providing a composition comprising at least one block poly(alkylene oxide) copolymer and a mixture of single-walled carbon nanotubes, said mixture comprising metallic and semiconducting single-walled nanotubes;

centrifuging said composition in said fluid medium for at least one of a time and at a rotational rate sufficient to form said density gradient in said fluid medium, said block poly(alkylene oxide) copolymer inducing a nanotube buoyant density approximating a density along said density gradient; and

separating said nanotube composition into at least one separation fraction enriched with one of said metallic and semiconducting single-walled nanotubes, said enrichment relative to said single-walled carbon nanotube composition.

14. The method of claim 13 wherein a said block poly(alkylene oxide) copolymer is selected from linear and X-shaped block poly(alkylene oxide) copolymers and combinations thereof.

15. The method of claim 14 wherein a said linear block copolymer comprises poly(ethylene oxide) and poly(propylene oxide) blocks.

16. The method of claim 15 wherein a said poly(ethylene oxide) block of a said linear block copolymer has a length greater than about 50 monomeric units.

17. The method of claim 16 wherein a said poly(propylene oxide) block of a said linear block copolymer has a length shorter than about 35 monomeric units.

18. The method of claim 15 comprising isolating at least one of said of least one separation fraction enriched with semiconducting single-walled carbon nanotubes.

19. The method of claim 14 wherein an X-shaped block poly(alkylene oxide) copolymer comprises poly(ethylene oxide) and poly(propylene oxide) blocks.

20. The method of claim 19 wherein a said poly(ethylene oxide) block of a said X-shaped block copolymer has a length greater than about 10 monomeric units.

21. The method of claim 20 wherein a said poly(propylene oxide) block of a said X-shaped block copolymer has a length greater than about 30 monomeric units.

22. The method of claim 19 comprising isolating at least one of said of least one separation fraction enriched with metallic single-walled carbon nanotubes.

23. The method of claim 13 wherein said fluid medium comprises aqueous iodixanol.

24. The method of claim 23 wherein a said block poly(alkylene oxide) copolymer is present at a concentration up to about 1% w/v in said fluid medium.

25. The method of claim 13 comprising isolation of at least one of said of least one separation fraction and deposition of said single-walled carbon nanotubes on a substrate.

26. A method of separating single-walled carbon nanotubes, said method comprising:

providing a fluid medium capable of forming a density gradient therein under centrifugation;

providing a composition comprising a single linear block poly(alkylene oxide) copolymer and a mixture of single-walled carbon nanotubes, said mixture comprising metallic and semiconducting nanotubes;

centrifuging said composition in said fluid medium for at least one of a time and at a rotational rate sufficient to form said density gradient in said fluid medium, said linear block poly(alkylene oxide) copolymer inducing a nanotube buoyant density approximating a density along said density gradient; and

separating said nanotube composition into at least one separation fraction enriched with semiconducting single-walled carbon nanotubes, said enrichment relative to said single-walled carbon nanotubes in said composition.

27. The method of claim 26 wherein a said linear block poly(alkylene oxide) copolymer comprises two poly(ethylene oxide) blocks and one poly(propylene oxide block, and a poly(ethylene oxide) block of said copolymer has a length greater than about 50 monomeric units.

28. The method of claim 27 wherein the poly(propylene oxide) block has a length shorter than about 35 monomeric units.

29. The method of claim 26 wherein said fluid medium comprises about 35%-about 40% iodixanol (w/v) in water.

30. The method of claim 29 wherein said fluid medium comprises about 35% iodixanol (w/v) and said composition is centrifuged less than about 10 hours.

31. The method of claim 30 wherein said composition is centrifuged about 4 hours to provide said at least one separation fraction comprising about 99.9% pure semiconducting single-walled carbon nanotubes.