Length-based liquid-liquid extraction of carbon nanotubes using a phase transfer catalyst

1. A method for separating SWNTs on a basis of length, said method comprising the steps of:

a) preparing functionalized SWNTs;

wherein the functionalized SWNTs are functionalized with ionizable functional moieties;

b) dissolving said functionalized SWNTs in a polar solvent to form a polar phase;

c) dissolving an amount of a phase transfer agent in a non-polar solvent to form a non-polar phase;

wherein said amount is substoichiometric in relation to the ionizable functional moieties;

d) combining the polar phase and the non-polar phase to form a bi-phase mixture;

e) adding a cationic donor species to the bi-phase mixture; and

f) agitating the bi-phase mixture;

wherein the phase transfer agent is electrostatically coupled with at least a portion of the ionizable functional moieties within the bi-phase mixture; and

wherein said agitating effects a preferential transport of short SWNTs into the non-polar phase to produce a non-polar phase enriched in short SWNTs and a polar phase enriched in longer SWNTs.

2. The method of claim 1 , wherein the ionizable functional moieties comprise sulfonic acid groups.

3. The method of claim 2 , wherein the ionizable functional moieties comprise chlorobenzenesulfonic acid groups.

4. The method of claim 1 , wherein the polar solvent is water.

5. The method of claim 1 , wherein the phase transfer agent is TOAB.

6. The method of claim 1 , wherein the non-polar solvent is selected from the group consisting of ethyl acetate, toluene, chloroform, benzene, and combinations thereof.

7. The method of claim 1 , wherein the cationic donor species is selected from the group consisting of NH 4 Cl, NH 4 Br, NaCl, and combinations thereof.

8. The method of claim 1 , wherein the cationic donor species is electrostatically coupled with at least a portion of the ionizable functional moieties.

9. The method of claim 1 , wherein the agitating step is accomplished by shaking.

10. The method of claim 1 , wherein the agitating step forms an emulsion.

11. The method of claim 10 , wherein the emulsion is stable.

12. The method of claim 11 , further comprising the steps of:

a) freezing the emulsion; and

b) thawing the emulsion;

wherein the step of freezing and the step of thawing break the emulsion.

13. The method of claim 1 , further comprising separating the non-polar phase enriched in short SWNTs from the polar phase enriched in longer SWNTs.

14. The method of claim 13 , further comprising filtering the non-polar phase enriched in short SWNTs to collect a short SWNT fraction.

15. The method of claim 14 , further comprising repeating the steps of claim 1 on the short SWNT fraction to provide a further separation of short SWNTs on a basis of length.

16. The method of claim 13 , further comprising filtering the polar phase enriched in longer SWNTs to collect a longer SWNT fraction.

17. The method of claim 16 , further comprising repeating the steps of claim 1 on the longer SWNT fraction to provide a further separation of longer SWNTs on a basis of length.

18. The method of claim 12 , further comprising separating the non-polar polar phase enriched in short SWNTs from the polar phase enriched in longer SWNTs.

19. The method of claim 18 , further comprising filtering the non-polar phase enriched in short SWNTs to collect a short SWNT fraction.

20. The method of claim 1 , further comprising adding a flocculating agent to the non-polar phase enriched in short SWNTs.

21. The method of claim 20 , wherein the flocculating agent comprises acetic acid.

22. The method of claim 1 , wherein the ionizable functional moieties comprise carboxylic acid-containing functional groups.

23. A method for separating CNTs on a basis of length, said method comprising the steps of:

a) preparing functionalized CNTs;

wherein the functionalized CNTs are functionalized with ionizable functional moieties;

b) dissolving said functionalized CNTs in a polar solvent to form a polar phase;

c) dissolving an amount of a phase transfer agent in a non-polar solvent to form a non-polar phase;

wherein said amount is substoichiometric in relation to the ionizable functional moieties;

d) combining the polar phase and the non-polar phase to form a bi-phase mixture;

e) adding a cationic donor species to the bi-phase mixture; and

f) agitating the bi-phase mixture;

wherein the phase transfer agent is electrostatically coupled with at least a portion of the ionizable functional moieties within the bi-phase mixture; and

wherein said agitating effects a preferential transport of short CNTs into the non-polar phase to produce a non-polar phase enriched in short CNTs and a polar phase enriched in longer CNTs.

24. A method for separating 1-dimensional nanostructures on a basis of length, said method comprising the steps of:

a) preparing functionalized 1-dimensional nanostructures;

wherein the functionalized 1-dimensional nanostructures are functionalized with ionizable functional moieties;

b) dissolving said functionalized 1-dimensional nanostructures in a polar solvent to form a polar phase;

c) dissolving a substoichiometric amount of a phase transfer agent in a non-polar solvent to form a non-polar phase;

wherein said amount is substoichiometric in relation to the ionizable functional moieties;

d) combining the polar phase and the non-polar phase to form a bi-phase mixture;

e) adding a cationic donor species to the bi-phase mixture; and

f) agitating the bi-phase mixture;

wherein the phase transfer agent is electrostatically coupled with at least a portion of the ionizable functional moieties within the bi-phase mixture; and

wherein said agitating effects a preferential transport of short 1-dimensional nanostructures into the non-polar phase to produce a non-polar phase enriched in short 1-dimensional nanostructures and a polar phase enriched in longer 1-dimensional nanostructures.