Compositions comprising free-standing two-dimensional nanocrystals

1. A polymer composite comprising:

(a) an organic polymer; and

(b) a planar MXene composition comprising at least one layer having first and second surfaces, each layer comprising:

a substantially two-dimensional array of crystal cells,

each crystal cell having an empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M,

wherein M is at least one Group IIIB, IVB, VB, or VIB metal,

wherein each X is C, N, or a combination thereof and

n=1, 2, or 3;

wherein at least one of said surfaces of each layer has surface terminations comprising alkoxide, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide, thiol, or a combination thereof;

wherein the planar MXene composition is distributed within the polymer.

2. The polymer composite of claim 1 , wherein the organic polymer comprises a thermoset or thermoplastic polymer or polymer resin, elastomer, or mixtures thereof.

3. The polymer composite of claim 1 , wherein the organic polymer comprises an aromatic or heteroaromatic moiety within the polymer.

4. The polymer composite of claim 3 , wherein the aromatic or heteroaromatic moiety within the polymer is phenyl, biphenyl, pyridinyl, bipyridinyl, naphthyl, or pyrimidinyl.

5. The polymer composite of claim 1 , wherein the organic polymer comprises an anisotropic polymer that is directionally oriented to be parallel in a polymer composite composition.

6. The polymer composite of claim 5 , wherein the anisotropic polymer is a liquid crystal polymer.

7. The polymer composite of claim 1 , wherein the organic polymer comprises an amide or ester derivative of terephthalic acid or naphthalic acid.

8. The polymer composite of claim 1 , wherein the organic polymer comprises polyethylene, polypropylene, polyethylenenaphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether etherketone (PEEK), polyamide, polyaryletherketone (PAEK), polyethersulfone (PES), polyethylenenimine (PEI), poly (p-phenylene sulfide) (PPS), polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyvinylidene difluoride (PVDF), or a polyvinyl fluoride (PVF).

9. The polymer composite of claim 1 wherein the planar MXene composition is present in the organic polymer in an amount ranging from about 0.1 wt % to about 50 wt %, relative to the combined weight of the organic polymer and planar MXene composition.

10. The polymer composite of claim 1 , wherein the polymer composite is in a form having a planar configuration, and the organic polymer is oriented in a plane coincident with the plane of that planar configuration.

11. The polymer composite of claim 10 , wherein the substantially two-dimensional array of crystal cells of the MXene composition defines a plane, and this plane is substantially aligned with plane of the oriented polymer coincident with the plane of the polymer composite.

12. The polymer composite claim 11 , the polymer composite having a flexural strength that is greater than the flexural strength of a corresponding polymer without the presence of the planar MXene composition.

13. The polymer composite claim 11 , the polymer composite having a stiffness that is greater than the stiffness of a corresponding polymer without the presence of the planar MXene composition.

14. The polymer composite of claim 1 , wherein the M n+1 X n comprises Sc 2 C, Sc 2 N, Ti 2 C, Ti 2 N, Mo 2 C, V 2 C, V 2 N, Cr 2 C, Cr 2 N, Zr 2 C, Zr 2 N, Nb 2 C, Nb 2 N, Hf 2 C, Hf 2 N, Ti 3 C 2 , Ti 3 N 2 , V 3 C 2 , V 3 C 2 , Ta 3 C 2 , Ta 3 N 2 , or Ti 4 C 3 , Ti 4 N 3 , V 4 C 3 , V 4 N 3 , Ta 4 C 3 ,Ta 4 N 3 , or a combination thereof.

15. The polymer composite of claim 1 , wherein the M n+1 X n comprises Ti 3 C 2 , Ti 3 CN, Ti 2 C, Ta 4 C 3 , or (V 1/2 Cr 1/2 ) 3 C 2 .

16. A conductive composition comprising

a planar MXene composition comprising at least one layer having first and second surfaces, each layer comprising:

a substantially two-dimensional array of crystal cells,

each crystal cell having an empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M,

wherein M is at least one Group IIIB, IVB, VB, or VIB metal,

wherein each X is C, N, or a combination thereof and

n=1, 2, or 3;

wherein at least one of said surfaces of each layer has surface terminations comprising alkoxide, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide, thiol, or a combination thereof;

said assembly having thickness of from 15 nm to 75 nm and a surface resistivity of less than about 50 micro-ohm-meter.

17. The conductive composition of claim 16 , wherein the stacked assembly is at least 65% tranparent to at least one wavelength of light in a range of from about 250 nm to about 850 nm.

18. The conductive composition of claim 17 , wherein the stacked assembly is at least 95% tranparent to at least one wavelength of light in a range of from about 250 nm to about 850 nm.

19. The conductive composition of claim 17 , wherein the M n+1 X n comprises Sc 2 C, Sc 2 N, Ti 2 C, Ti 2 N, Mo 2 C, V 2 C, V 2 N, Cr 2 C, Cr 2 N, Zr 2 C, Zr 2 N, Nb 2 C, Nb 2 N, Hf 2 C, Hf 2 N, Ti 3 C 2 , Ti 3 N 2 , V 3 C 2 , V 3 C 2 , Ta 3 C 2 , Ta 3 N 2 , or Ti 4 C 3 , Ti 4 N 3 , V 4 C 3 , V 4 N 3 , Ta 4 C 3 ,Ta 4 N 3 , or a combination thereof.

20. The conductive composition of claim 16 , wherein M n+1 X n comprises Ti 3 C 2 , Ti 3 CN, or Ti 2 C.

21. An electronic device comprising a stacked assembly of at least two layers having first and second surfaces, each layer comprising:

a substantially two-dimensional array of crystal cells,

each crystal cell having the empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M;

wherein M is a Group IIIB, IVB, VB, or VIB metal;

each X is C, N, or a combination thereof; and

n=1, 2, or 3;

wherein at least one of said surfaces of each layer has bound thereto surface terminations comprising alkoxide, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide, nitride, subnitride, sulfide, thiol, or a combination thereof;

said stacked assembly having a surface resistivity of less than about 50 micro-ohm-meter.

22. The electronic device of claim 21 , wherein the stacked assembly exhibits at least 65% tranparency to at least one wavelength of light in a range of from about 250 nm to about 850 nm.

23. The electronic device of claim 21 , wherein the stacked assembly further comprises intercalated lithium, sodium, potassium, cesium, ammonium, magnesium, or aluminum ions.

24. The electronic device of claim 23 , wherein the stacked assembly further comprises intercalated hydrazine, hydrazine monohydrate, DMSO, urea, or N, N-dimethylformamide.

25. The electronic device of claim 21 , wherein M n+1 X n comprises Sc 2 C, Sc 2 N, Ti 2 C, Ti 2 N, Mo 2 C, V 2 C, V 2 N, Cr 2 C, Cr 2 N, Zr 2 C, Zr 2 N, Nb 2 C, Nb 2 N, Hf 2 C, Hf 2 N, Ti 3 C 2 , Ti 3 N 2 , V 3 C 2 , V 3 C 2 , Ta 3 C 2 , Ta 3 N 2 , or Ti 4 C 3 , Ti 4 N 3 , V 4 C 3 , V 4 N 3 , Ta 4 C 3 ,Ta 4 N 3 , or a combination thereof.

26. The electronic device of claim 21 , wherein M n+1 X n comprises Ti 3 C 2 , TiNbC, Ti 3 CN, or Ti 2 C.

27. An electronic device of claim 23 that is an ion battery.

28. An electronic device of claim 23 that is a lithium ion battery.

29. An electronic device of claim 23 that is a metal-ion capacitor.

30. A suspension of delaminated flakes, the flakes comprising MXene compositions comprising:

at least one layer having first and second surfaces, each layer comprising:

a substantially two-dimensional array of crystal cells,

each crystal cell having an empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M,

wherein M is at least one Group IIIB, IVB, VB, or VIB metal,

wherein each X is C, N, or a combination thereof and

n=1, 2, or 3;

wherein at least one of said surfaces of each layer has surface terminations comprising alkoxide, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide, thiol, or a combination thereof.

31. The suspension of claim 30 , wherein M n+1 X n comprises Sc 2 C, Sc 2 N, Ti 2 C, Ti 2 N, Mo 2 C, V 2 C, V 2 N, Cr 2 C, Cr 2 N, Zr 2 C, Zr 2 N, Nb 2 C, Nb 2 N, Hf 2 C, Hf 2 N, Ti 3 C 2 , Ti 3 N 2 , V 3 C 2 , V 3 C 2 , Ta 3 C 2 , Ta 3 N 2 , or Ti 4 C 3 , Ti 4 N 3 , V 4 C 3 , V 4 N 3 , Ta 4 C 3 ,Ta 4 N 3 , or a combination thereof.

32. The suspension of claim 26 , wherein M n+1 X n comprises Ti 3 C 2 , Ti 3 CN, Ti 2 C, Ta 4 C 3 , or (V 1/2 Cr 1/2 ) 3 C 2 .

33. The suspension of claim 30 , wherein the delaminated flakes are suspended in an aqueous medium.

34. The suspension of claim 30 , wherein the delaminated flakes are suspended in isopropanol.