Nanocrystals including III-V semiconductors

1. A water-soluble semiconductor nanocrystal comprising a core including a first semiconductor material, the first semiconductor material being a III-V alloy having the formula M 1 i M 2 J E 1 x E 2 y , wherein M 1 and M 2 are each independently a group III element; E 1 and E 2 are each independently a group V element; wherein (a) neither i nor j is zero, or (b) neither x nor y is zero; and the hydrodynamic diameter of the semiconductor nanocrystal is between 5 nm and 15 nm, and wherein the nanocrystal has an emission wavelength in a range of 700 to 1000 nm.

2. The semiconductor nanocrystal of claim 1 , wherein the first semiconductor material includes indium or gallium.

3. The semiconductor nanocrystal of claim 2 , wherein the first semiconductor material includes nitrogen, phosphorus, arsenic, or antimony.

4. The semiconductor nanocrystal of claim 1 , further comprising an overcoating on a surface of the core, the overcoating including a second semiconductor material.

5. The semiconductor nanocrystal of claim 4 , wherein the second semiconductor material includes a II-VI or a III-V semiconductor material.

6. The semiconductor nanocrystal of claim 4 , further comprising a second overcoating on a surface of the core, the overcoating including a third semiconductor material.

7. The semiconductor nanocrystal of claim 6 , wherein the second semiconductor material is a III-V semiconductor material and the third semiconductor material is a II-VI semiconductor material.

8. The semiconductor nanocrystal of claim 1 , further comprising a ligand on a surface of the semiconductor nanocrystal.

9. The semiconductor nanocrystal of claim 8 , wherein the semiconductor nanocrystal has a hydrodynamic diameter of less than 15 nm.

10. The semiconductor nanocrystal of claim 1 , where the ligand is selected to render the semiconductor nanocrystal water soluble.

11. A water-soluble semiconductor nanocrystal comprising:

a core including a first semiconductor material, the first semiconductor material being a III-V alloy having the formula M 1 i M 2 j E 1 x E 2 y , wherein M 1 and M 2 are each independently a group III element; E 1 and E 2 are each independently a group V element; and i, j, x and y are each independently a non-negative number, wherein (a) neither i nor j is zero, or (b) neither x nor y is zero; and the hydrodynamic diameter of the semiconductor nanocrystal is between 5 nm and 15 nm;

a first overcoating including a second semiconductor material on a surface of the core; and

a second overcoating including a third semiconductor material on a surface of the first overcoating, and wherein the nanocrystal has an emission wavelength in a range of 700 to 1000 nm.

12. The semiconductor nanocrystal of claim 11 , wherein the second semiconductor material is selected to electronically passivate the core.

13. The semiconductor nanocrystal of claim 12 , wherein the third semiconductor material is selected to chemically stabilize the first overcoating.

14. The semiconductor nanocrystal of claim 11 , wherein the first overcoating includes a III-V semiconductor material.

15. The semiconductor nanocrystal of claim 14 , wherein the second overcoating includes a II-VI semiconductor material.

16. The semiconductor nanocrystal of claim 11 , further comprising a ligand on a surface of the semiconductor nanocrystal.

17. The semiconductor nanocrystal of claim 16 , wherein the semiconductor nanocrystal has a hydrodynamic diameter of less than 15 nm.

18. The semiconductor nanocrystal of claim 11 , where the ligand is selected to render the semiconductor nanocrystal water soluble.

19. A water-soluble semiconductor nanocrystal comprising:

a core including a first semiconductor material; and

an overcoating including a second semiconductor material on a surface of the core; wherein the second semiconductor material includes a II-VI alloy having the formula M 1 i M 2 j E 1 x E 2 y , wherein M 1 and M 2 are each independently a group II element; E 1 and E 2 are each independently a group VI element; and i, j, x and y are each independently a non-negative number, wherein (a) neither i nor j is zero, or (b) neither x nor y is zero; wherein the hydrodynamic diameter of the semiconductor nanocrystal is between 5 nm and 15 nm, and wherein the nanocrystal has an emission wavelength in a range of 700 to 1000 nm.

20. The semiconductor nanocrystal of claim 19 , wherein the first semiconductor material includes a III-V semiconductor material.

21. The semiconductor nanocrystal of claim 19 , further comprising a ligand on a surface of the semiconductor nanocrystal.

22. The semiconductor nanocrystal of claim 21 , wherein the semiconductor nanocrystal has a hydrodynamic diameter of less than 15 nm.

23. The semiconductor nanocrystal of claim 19 , where the ligand is selected to render the semiconductor nanocrystal water soluble.

24. A water-soluble fluorescent particle comprising:

a semiconductor nanocrystal including a III-V semiconductor material and a II-VI semiconductor, material wherein the III-V semiconductor material is an alloy having the formula M 1 i M 2 j E 1 x E 2 y , wherein M 1 and M 2 are each independently a group III element; E 1 and E 2 are each independently a group V element; and i, j, x and y are each independently a non-negative number, wherein (a) neither i nor j is zero, or (b) neither x nor y is zero; and

a ligand on a surface of the semiconductor nanocrystal;

wherein the particle has a hydrodynamic diameter not greater than 15 nm, and wherein the nanocrystal has an emission wavelength in a range of 700 to 1000 nm.

25. The fluorescent particle of claim 24 , wherein the particle has a diameter between 10 nm and 15 nm.

26. The fluorescent particle of claim 24 , wherein the semiconductor nanocrystal includes a core including the III-V semiconductor material and an overcoating on a surface of the core, the overcoating including the II-VI semiconductor material.

27. The semiconductor nanocrystal of claim 24 , where the ligand is selected to render the semiconductor nanocrystal water soluble.

28. A water-soluble semiconductor nanocrystal comprising a core including a first semiconductor material having the formula M 1 E 1 x E 2 1−x , wherein M 1 is a group III element; E 1 and E 2 are each independently a group V element; and x is a non-negative number; and the hydrodynamic diameter of the semiconductor nanocrystal is between 5 nm and 15 nm, and wherein the nanocrystal has an emission wavelength in a range of 700 to 1000 nm.

29. The semiconductor nanocrystal of claim 28 , wherein M 1 is indium or gallium.

30. The semiconductor nanocrystal of claim 29 , wherein each of E 1 and E 2 , independently, are nitrogen, phosphorus, arsenic, or antimony.

31. The semiconductor nanocrystal of claim 30 , wherein 0<x <1.

32. The semiconductor nanocrystal of claim 31 , wherein M 1 is indium.

33. The semiconductor nanocrystal of claim 32 , wherein E 1 is arsenic.

34. The semiconductor nanocrystal of claim 33 , wherein E 2 is phosphorus.

35. The semiconductor nanocrystal of claim 34 , wherein 0.33 ≦x≦0.82.

36. The semiconductor nanocrystal of claim 28 , further comprising an overcoating on a surface of the core, the overcoating including a second semiconductor material.

37. The semiconductor nanocrystal of claim 36 , wherein the second semiconductor material includes a II-VI or a III-V semiconductor material.

38. The semiconductor nanocrystal of claim 36 , further comprising a second overcoating on a surface of the core, the overcoating including a third semiconductor material.

39. The semiconductor nanocrystal of claim 38 , wherein the second semiconductor material is a III-V semiconductor material and the third semiconductor material is a II-VI semiconductor material.

40. The semiconductor nanocrystal of claim 28 , further comprising a ligand on a surface of the semiconductor nanocrystal.

41. The semiconductor nanocrystal of claim 40 , wherein the semiconductor nanocrystal has a hydrodynamic diameter of less than 15 nm.

42. The semiconductor nanocrystal of claim 28 , where the ligand is selected to render the semiconductor nanocrystal water soluble.

43. A water-soluble semiconductor nanocrystal comprising:

a core including a first semiconductor material, the first semiconductor material being a III-V alloy having the formula M 1 i M 2 J E 1 x E 2 y , wherein M 1 and M 2 are each independently a group III element; E 1 and E 2 are each independently a group V element; wherein (a) neither i nor j is zero, or (b) neither x nor y is zero;

an overcoating on a surface of the core, the overcoating including a second semiconductor material, wherein the second semiconductor material includes a III-V semiconductor material; and

a second overcoating on a surface of the core, the overcoating including a third semiconductor material, wherein the third semiconductor material includes a II-VI semiconductor material; and the hydrodynamic diameter of the semiconductor nanocrystal is between 10 nm and 15 nm.

44. The semiconductor nanocrystal of claim 43 , wherein the first semiconductor material is InAs x P 1−x .

45. The semiconductor nanocrystal of claim 44 , wherein the second semiconductor material is InP.

46. The semiconductor nanocrystal of claim 45 , wherein the third semiconductor material is ZnSe.

47. The semiconductor nanocrystal of claims 43 , wherein the semiconductor nanocrystal has a hydrodynamic diameter of less than 15 nm.

48. A water-soluble semiconductor nanocrystal comprising a core including a first semiconductor material, the first semiconductor material being a III-V alloy having the formula M 1 i M 2 J E 1 x E 2 y , wherein M 1 and M 2 are each independently a group III element; E 1 and E 2 are each independently a group V element; wherein (a) neither i nor j is zero, or (b) neither x nor y is zero, and the emission wavelength of the nanocrystal is below 800 nm, and wherein the nanocrystal has a hydrodynamic diameter less than 15 nm.

49. The semiconductor nanocrystal of claim 48 , wherein the M 1 is indium or gallium.

50. The semiconductor nanocrystal of claim 49 , wherein each of E 1 and E 2 , independently, are nitrogen, phosphorus, arsenic, or antimony.

51. The semiconductor nanocrystal of claim 50 , wherein 0<x <1.

52. The semiconductor nanocrystal of claim 51 , wherein M 1 is indium.

53. The semiconductor nanocrystal of claim 52 , wherein E 1 is arsenic.

54. The semiconductor nanocrystal of claim 53 , wherein E 2 is phosphorus.

55. The semiconductor nanocrystal of claim 54 , wherein 0.33≦x≦0.82.

56. The semiconductor nanocrystal of claim 48 , further comprising an overcoating on a surface of the core, the overcoating including a second semiconductor material.

57. The semiconductor nanocrystal of claim 56 , wherein the second semiconductor material includes a II-VI or a III-V semiconductor material.

58. The semiconductor nanocrystal of claim 56 , further comprising a second overcoating on a surface of the core, the overcoating including a third semiconductor material.

59. The semiconductor nanocrystal of claim 58 , wherein the second semiconductor material is a III-V semiconductor material and the third semiconductor material is a II-VI semiconductor material.