Highly luminescent color-selective nano-crystalline materials

• US 6,322,901 B1
• Filed: 11/13/1997
• Issued: 11/27/2001
• Est. Priority Date: 11/13/1997
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Rodriguez-Viejo, Xavier, Bawendi, Moungi, Jensen, Klavs F., Dabbousi, Bashir O., Mikulec, Frederic Victor
• Primary Examiner(s): Le, H. Thi
• Application Number:
  US08/969,302
• Time in Patent Office: 1,475 Days
• Field of Search: 428/403, 428/548, 428/570, 428/551
• US Class Current: 428/548
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 17/20 Methods for preparing sulfides or polysulfides, in general ammonium sulfides or polysulfides C01C; sulfides or polysulfides of metals, other than alkali metals, magnesium, calcium, strontium and barium, see the relevant groups of subclasses C01F or C01G, according to the metal
• CPC Class Codes: C01B 19/007 Tellurides or selenides of metals C01B19/002 takes precedence
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2002/84 by UV- or VIS- data
• CPC Class Codes: C01P 2004/04 obtained by TEM, STEM, STM or AFM
• CPC Class Codes: C01P 2004/52 highly monodisperse size distribution
• CPC Class Codes: C01P 2004/86 Thin layer coatings, i.e. the coating thickness being less than 0.1 time the particle radius
• CPC Class Codes: C01P 2006/60 Optical properties, e.g. expressed in CIELAB-values
• CPC Class Codes: C09K 11/883 with zinc or cadmium
• CPC Class Codes: Y10T 428/12028 Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, etc.]
• CPC Class Codes: Y10T 428/12049 Nonmetal component
• CPC Class Codes: Y10T 428/12181 Composite powder [e.g., coated, etc.]
• CPC Class Codes: Y10T 428/2991 Coated

Abstract

A coated nanocrystal capable of light emission includes a substantially monodisperse nanoparticle selected from the group consisting of CdX, where x=S, Se, Te and an overcoating of ZnY, where Y=S, Se, uniformly deposited thereon, said coated nanoparticle characterized in that when irradiated the particles exhibit photoluminescence in a narrow spectral range of no greater than about 60 nm, and most preferably 40 nm, at full width half max (FWHM). The particle size of the nanocrystallite core is in the range of about 20 Åto about 125 Å, with a deviation of less than 10% in the core. The coated nanocrystal exhibits photoluminescence having quantum yields of greater than 30%.

Claims

1. A coated nanocrystal capable of light emission, comprising:

a core comprising a first semiconductor material, said core being a member of a monodisperse particle population; and

an overcoating uniformly deposited on the core comprising a second semiconductor material,

wherein the first semiconductor material and the second semiconductor material are the same or different,

and wherein the monodisperse particle population is characterized in that when irradiated the population emits light in a spectral range of no greater than about 60 nm full width at half max (FWHM).

2. The coated nanocrystal of claim 1, wherein the spectral range is not greater than about 40 nm full width at half max (FWHM).

3. The coated nanocrystal of claim 1, wherein the spectral range is not greater than about 30 nm full width at half max (FWHM).

4. The coated nanocrystal of claim 1, wherein the coated nanocrystal exhibits photoluminescence having quantum yields of greater than 30%.

5. The coated nanocrystal of claim 4, wherein the coated nanocrystal exhibits photoluminescence having quantum yields in the range of about 30% to 50%.

6. The coated nanocrystal of claim 1, wherein the spectral range is selected from the spectrum in the range of about 470 nm to about 620 nm.

7. The coated nanocrystal of claim 1, wherein the monodisperse particle population is characterized in that it exhibits no more than about 10% rms deviation in the diameter of the core.

8. The coated nanocrystal of claim 7, wherein the monodisperse particle population is characterized in that it exhibits no more than about 5% rms deviation in the diameter of the core.

9. The coated nanocrystal of claim 7 or 8, wherein the diameter of the core is in the range of about 20 Å

to about 125 Å

.

13. The coated nanocrystal of claim 1 or 10, wherein the overcoating comprises greater than about 0 to about 5.3 monolayers of the second semiconductor material.

14. The coated nanocrystal of claim 13, wherein the overcoating comprises less than about one monolayer of the second semiconductor material.

15. The coated nanocrystal of claim 14, wherein the second semiconductor material is ZnS or ZnSe.

16. The coated nanocrystal of claim 13, wherein the overcoating comprises in the range of about one to about two monolayers of the second semiconductor material.

17. The coated nanocrystal of claim 13, wherein the second semiconductor material is ZnS or ZnSe.

18. The coated nanocrystal of claim 1 or 10, wherein the nanocrystal further comprises an organic layer on the nanocrystal outer surface.

19. The coated nanocrystal of claim 18, wherein the organic layer comprises a moiety selected to provide compatibility with a suspension medium.

20. The coated nanocrystal of claim 18, wherein the organic layer comprises a moiety selected to exhibit affinity for the outer surface of the nanocrystal.

21. The coated nanocrystal of claim 20, wherein the organic layer comprises a short-chain polymer terminating in a moiety having affinity for a suspending medium.

22. The coated nanocrystal of claim 1 or 10, wherein the first semiconductor material is selected from the group consisting of CdS, CdSe, CdTe, and mixtures thereof.

23. The coated nanocrystal of claim 22, wherein the second semiconductor material is selected from the group consisting of ZnS, ZnSe, CdS, CdSe, and mixtures thereof.

24. The coated nanocrystal of claim 1 or 10, wherein the second semiconductor material is selected from the group consisting of ZnS, ZnSe, CdS, CdSe, and mixtures thereof.

25. The coated nanocrystal of claim 1 or 10, wherein the first semiconductor material is CdSe and the second semiconductor material is ZnS.

26. The coated nanocrystal of claim 25, wherein the overcoating comprises greater than about 0 to about 5.3 monolayers of the second semiconductor material.

27. The coated nanocrystal of claim 26, wherein the overcoating comprises less than about one monolayer of the second semiconductor material.

28. The coated nanocrystal of claim 27, wherein the second semiconductor material is ZnS or ZnSe.

29. The coated nanocrystal of claim 26, wherein the overcoating comprises in the range of about one to about two monolayers of the second semiconductor material.

30. The coated nanocrystal of claim 26, wherein the second semiconductor material is ZnS or ZnSe.

31. The coated nanocrystal of claim 1 or 10, wherein said coated nanocrystal is a member of a substantially monodisperse particle population.

10. A coated nanocrystal capable of light emission, comprising:

a core comprising a first semiconductor material, said core being a member of a monodisperse particle population; and

an overcoating uniformly deposited on the core comprising a second semiconductor material,

wherein the first semiconductor material and the second semiconductor material are the same or different,

and wherein the monodisperse particle population is characterized in that it exhibits no more than about a 10% rms deviation in the diameter of the core.

11. The coated nanocrystal of claim 10, wherein the coated nanocrystal exhibits less than a 5% rms deviation in diameter of the core.

12. The coated nanocrystal of claim 11 or 10, wherein the diameter of the core is in the range of about 20 Å

to about 125 Å

.