Polymer-conjugated quantum dots and methods of making the same

1. A quantum dot comprising:

an inorganic core; and a shell, wherein the shell comprises a polymer conjugated to the inorganic core, the polymer comprising a first monomer unit represented by formula I and a second monomer unit represented by formula II:

wherein R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of hydrogen, R 9 , C 1-6 alkyl, and C 1-6 alkyl substituted with one or more of R 9 , provided that at least one of R 1 , R 2 , R 3 , and R 4 is R 9 or C 1-6 alkyl substituted with one of or more of R 9 ;

wherein each R 9 is independently represented by formula III:

wherein R 10 is independently selected from the group consisting of hydrogen, C 1-6 alkyl, and C 1-6 alkyl substituted with one or more hydroxyl;

wherein each R 11 is independently selected from the group consisting of hydrogen, methyl, and combinations thereof;

wherein n is from 0 to 200;

wherein R 5 , R 6 , R 7 , and R 8 are each independently selected from the group consisting of hydrogen, R 12 , C 1-6 alkyl, and C 1-6 alkyl substituted with one or more of R 12 , provided that at least one of R 5 , R 6 , R 7 , and R 8 is R 12 or C 1-6 alkyl substituted with one or more of R 12 ;

wherein each R 12 is independently represented by formula IV:

wherein each X 1 is —C 1-6 alkylene-; and

wherein the molar ratio of R 9 to R 12 substitutions in the polymer is in the range of about 94:6 to about 75:25.

2. The quantum dot of claim 1 , wherein the polymer is water-soluble.

3. The quantum dot of claim 1 , wherein n is 0 and R 10 is hydrogen.

4. The quantum dot of claim 1 , R 1 , R 2 , R 3 , R 5 , R 6 , and R 7 are hydrogen.

5. The quantum dot of claim 1 , wherein X 1 is ethylene.

6. The quantum dot of claim 1 , wherein the polymer comprises about 1 to about 10 monomer units that are substituted with R 12 .

7. The quantum dot of claim 1 , wherein the polymer has a weight average molecular weight of at least about 500 Da.

8. The quantum dot of claim 1 , wherein the polymer comprises at least about 90% by mole of a combined amount of the first monomer unit and the second monomer unit.

9. The quantum dot of claim 1 , wherein the inorganic core comprises an element selected from the group consisting of Cd, Se, S, Te, Zn, and combinations thereof.

10. The quantum dot of claim 1 , wherein the inorganic core comprises an inner core and one or more outer layers, the inner core comprising a inorganic material that is luminescent, and the one or more outer layers comprising a inorganic material that exhibits a high bandgap.

11. The quantum dot of claim 1 , wherein the inorganic core has a diameter less than about 30 nm.

12. The quantum dot of claim 1 , wherein the shell has a hydrodynamic thickness of less than or equal to about 20 nm.

13. The quantum dot of claim 1 , wherein the quantum dot maintains at least 80% luminescence intensity when dispersed in aqueous solution for about 5 days.

14. A method of making a quantum dot of claim 1 comprising:

conjugating an inorganic core with a polymer comprising a first monomer unit represented by formula I and a second monomer unit represented by formula II:

wherein R 1 , R 2 , R 3 , and R 4 are each independently selected from the group consisting of hydrogen, R 9 , C 1-6 alkyl, and C 1-6 alkyl substituted with one or more of R 9 , provided that at least one of R 1 , R 2 , R 3 , and R 4 is R 9 or C 1-6 alkyl substituted with one or more of R 9 ;

wherein each R 9 is independently represented by formula III:

wherein R 10 is independently selected from the group consisting of hydrogen, C 1-6 alkyl, and C 1-6 alkyl substituted with one or more hydroxy;

wherein each R 11 is independently selected from the group consisting of hydrogen, methyl, and combinations thereof;

wherein n is from 0 to 200;

wherein R 5 , R 6 , R 7 , and R 8 are each independently selected from the group consisting of hydrogen, R 12 , C 1-6 alkyl, and C 1-6 alkyl substituted with one or more of R 12 , provided that at least one of R 5 , R 6 , R 7 , and R 8 is R 12 or C 1-6 alkyl substituted with one or more of R 12 ; and

wherein each R 12 is independently represented by formula IV:

wherein each X 1 is —C 1-6 alkylene-.

15. The method of claim 14 , wherein the molar ratio of R 9 to R 12 substitutions in the polymer is in the range of about 94:6 to about 75:25.

16. The method of claim 14 , wherein the polymer comprises R 12 before conjugating with the quantum dot.

17. The method of claim 14 , wherein the method does not include conjugating the quantum dot with a compound represented by formula V:

wherein X 2 is —C 1-6 alkylene-.

18. A method comprising exposing a composition comprising the quantum dot of claim 1 to a radiation that is effective to produce luminescence.

19. The method of claim 18 , further comprising detecting the luminescence produced from the quantum dot.

20. The method of claim 18 , further comprising measuring luminescence intensity produced from the quantum dot and correlating the luminescence intensity with a concentration of quantum dots in the composition.

21. A method for detecting a component within a system, the method comprising:

providing the quantum dot of claim 1 to the system, wherein the quantum dot further comprises one or more molecules conjugated to the polymer, wherein the one or more molecules have affinity for the component;

exposing the system to radiation that is effective to produce luminescence from the quantum dot; and

measuring the intensity of radiation emitted by the quantum dots, wherein an increased intensity correlates with the presence of the component.

22. The method of claim 21 , wherein the system is a biological system.

23. The method of claim 22 , wherein the molecule is selected from the group consisting of an antibody, a ligand, a receptor, and nucleic acid.

24. The method of claim 23 , wherein the molecule has affinity for a target on the component, wherein the target is selected from the group consisting of an antigen, a receptor, ligand, a nucleic acid.