Water-soluble fluorescent semiconductor nanocrystals

• US 6,319,426 B1
• Filed: 09/17/1999
• Issued: 11/20/2001
• Est. Priority Date: 09/18/1998
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Lee, Jin-Kyu, Bawendi, Moungi G., Mikulec, Frederic V.
• Primary Examiner(s): Koslow, C. Melissa
• Application Number:
  US09/397,428
• Time in Patent Office: 795 Days
• Field of Search: 252/301.4 R, 252/301.4 S, 252/301.6 R, 252/301.6 S, 428/403, 428/407, 428/690
• US Class Current: 252/301.40R
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C01B 19/007 Tellurides or selenides of metals C01B19/002 takes precedence
• CPC Class Codes: C01P 2004/64 Nanometer sized, i.e. from 1-100 nanometer
• CPC Class Codes: G01N 33/533 with fluorescent label
• CPC Class Codes: G01N 33/588 with semiconductor nanocrystal label, e.g. quantum dots
• CPC Class Codes: Y10T 428/2991 Coated
• CPC Class Codes: Y10T 428/2998 including synthetic resin or polymer

Abstract

A water-soluble semiconductor nanocrystal capable of light emission is provided. The nanocrystal including a semiconductor nanocrystal core having a selected band gap energy, a shell layer overcoating the core comprised of a semiconductor material having a band gap energy greater than that of the semiconductor nanocrystal, and an outer layer comprised of a molecule having at least one linking group for attachment of the molecule to the overcoating shell layer and at least one hydrophilic group optionally spaced apart from the linking group by a hydrophobic region sufficient to prevent electron charge transfer across the hydrophobic region.

Claims

1. A water-soluble semiconductor nanocrystal capable of energy emission, comprising:

a semiconductor nanocrystal core having a selected band gap energy;

a shell layer overcoating the semiconductor nanocrystal core, the shell comprised of a semiconductor material having a band gap energy greater than that of the core;

an outer layer comprising a molecule having a first portion comprising at least two linking groups for attachment to the nanocrystal and a second portion comprising at least one hydrophilic group.

3. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule has structural formula (I),

4. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule has structural formula (II),

wherein:

Y is the hydrophilic moiety;

Z is a hydrophobic region having a backbone of at least six atoms;

X and X′

are individually or together the linking groups, are the same or different and are selected from the group of S, N, P and O═

P, each of X and X′

optionally including other substituents in order to satisfy valence requirements and atoms bridging X and X′

are selected to form a 5-membered to 8-membered ring upon coordination to the nanocrystal surface.

5. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule has structural formula (III),

wherein:

Y is the hydrophilic moiety;

Z is a hydrophobic region having a backbone of at least six atoms;

X, X′ and

X″

are individually or together linking groups, are the same or different and are selected from the group of S, N, P and O═

P, each of X, X′ and

X″

optionally including other substituents in order to satisfy valence requirements, and atoms bridging X and X′

are selected to form a 5-membered to 8-membered ring upon coordination to the semiconductor surface, atoms bridging X and X″

are selected to form a 5-membered to 8-membered ring upon coordination to the semiconductor surface, and atoms bridging X′ and

X″

are selected to form a 5-membered to 8-membered ring upon coordination to the nanocrystal surface.

6. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule has the structural formula (IV),

7. The water-soluble nanocrystal of claim 6, wherein R¹ is a thiol, a phosphine, a phosphine oxide, or an amine.

8. The water-soluble nanocrystal of claim 6, wherein R² contains between 6 and 20 atoms.

9. The water-soluble nanocrystal of claim 8, wherein R² is a linear alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, a cycloalkyl or a heterocyclic.

10. The water-soluble nanocrystal of claim 6, wherein b is 1, 2 or 3, and R³ contains between 6 and 20 atoms.

11. The water-soluble nanocrystal of claim 10, wherein R³ is a linear alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, a cycloalkyl or heterocyclic.

12. The water-soluble nanocrystal of claim 6, wherein R⁴ is a carboxylate, a phosphonate, a sulfonate or an ammonium.

13. The water-soluble nanocrystal of claim 6, wherein the molecule is a multidentate ligand.

14. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule comprises structural formula (V),

15. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule comprises the formula,

wherein:

the Xs are the same or different and are selected from the group consisting of S, N, P and O═

P, and optionally include other substituents to satisfy valence requirements;

the Ys are a hydrophilic moiety;

R is H or a polar moiety;

R′

is H or a non-polar moiety;

m is in the range about 3 to 100; and

n is in the range about 3 to 100.

16. The water-soluble nanocrystal of claim 14, wherein the molecule is a multidentate ligand.

17. The water-soluble nanocrystal of claim 1 or 2, wherein the molecule is a multidentate ligand.

23. The water-soluble nanocrystal of claim 1, or 18, wherein the nanocrystal core is a Group II-VI, Group III-V or Group IV semiconductor.

24. The water-soluble nanocrystal of claim 23, wherein the core is a member of a monodisperse particle population.

25. The water-soluble nanocrystal of claim 24, wherein the monodisperse particle population is characterized in that when irradiated the population emits light in a spectral range less than about 40 nm full width at half maximum (FWHM).

26. The water-soluble nanocrystal of claim 25, wherein the monodisperse particle population is characterized in that when irradiated the population emits light in a spectral range less than about 25 nm full width at half maximum (FWHM).

27. The water-soluble nanocrystal of claim 24, 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.

28. The water-soluble nanocrystal of claim 27, wherein the monodisperse particle population is characterized in that it exhibits no more than about 5% rms deviation in the diameter of the core.

29. The water-soluble nanocrystal of claim 23, wherein the core comprises CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, MgTe, GaAs, GaP, GaSb, GaN, HgS, HgSe, HgTe, InAs, InP, InSb, InN, AlAs, AlP, AlSb, AlS, PbS, PbSe, Ge, Si, an alloy thereof, or a mixture thereof.

30. The water-soluble nanocrystal of claim 1 or 18, wherein the core comprises CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, MgTe, GaAs, Gap, GaSb, GaN, HgS, HgSe, HgTe, InAs, InP, InSb, InN, AlAs, AlP, AlSb, AlS, PbS, PbSe, Ge, Si, an alloy thereof, or a mixture thereof, and the shell comprises ZnO, ZnS, ZnSe, ZnTe, CdO, CdS, CdSe, CdTe, MgS, MgSe, GaAs, GaN, GaP, GaAs, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP, InSb, AlAs, AlN, AlP, AlSb, an alloy thereof, or a mixture thereof.

31. The water-soluble nanocrystal of claim 1 or 18, wherein the core is CdSe and the shell is ZnS.

2. A water-soluble semiconductor nanocrystal capable of energy emission, comprising:

a semiconductor nanocrystal core having a selected band gap energy; and

an outer layer comprising a molecule having a first portion comprising at least one linking group for attachment to the nanocrystal and a second portion comprising at least one hydrophilic group, the molecule being selected from the group consisting of;

a structure of formula (I),

18. A water-soluble semiconductor nanocrystal capable of energy emission, comprising:

a semiconductor nanocrystal core having a selected band gap energy;

a shell layer overcoating the semiconductor nanocrystal core, the shell comprised of a semiconductor material having a band gap energy greater than that of the semiconductor nanocrystal; and

a bilayer overcoating the shell, the bilayer comprising;

an inner layer having affinity for the shell; and

an outer layer comprising a molecule having a hydrophilic group spaced apart from the inner layer by a hydrophobic region adjacent to the inner layer.

19. The water-soluble nanocrystal of claim 18, wherein the inner layer comprises a coordinating lyophilic compound.

20. The water-soluble nanocrystal of claim 19, wherein the coordinating lyophilic compound is selected from the group consisting of trialkyl phosphines, trialkyl phosphine oxides, and alkyl amines.

21. The water-soluble nanocrystal of claim 18, wherein the outer layer comprises a surfactant.

22. The water-soluble nanocrystal of claim 21, wherein the surfactant is selected from the group consisting of sodium dioctyl sulfosuccinate, C₁₂H₂₅(OCH₂CH₂)₂₃OH, C₁₈H₃₇(OCH₂CH₂)₁₀OH and C₁₈H₃₇(OC₂CH₂)₂₀OH.