Passivated nanoparticles

1. A method for fabricating a passivated semiconductor nanocrystal, said method comprising the steps of:

synthesizing an alloy-gradient nanoparticle, said nanoparticle comprising Cd, S and Se;

applying a semiconductor coating comprising Zn and S over said alloy-gradient nanoparticle, said coating having a wider band gap than the alloy-gradient nanoparticle to provide a semiconductor coated alloy-gradient nanoparticle;

coating the surface of the semiconductor coated alloy-gradient nanoparticle by growing monolayers of aluminum on the surface of the semiconductor coated alloy-gradient nanoparticle; and

oxidizing the surface of said aluminum layer by exposure to an ambient environment to form an aluminum oxide layer thereon to provide a passivated semiconductor nanocrystal;

wherein the semiconductor coated alloy-gradient nanoparticle with the aluminum oxide layer has less of a reduction in fluorescence than a semiconductor coated alloy-gradient nanoparticle not having an aluminum oxide layer.

2. The method of claim 1 , wherein the semiconductor coating is a binary semiconductor coating.

3. The method of claim 1 , wherein the semiconductor coating is an alloy-gradient coating further comprising at least one additional different Group VI element.

4. The method of claim 1 , wherein the synthesizing step comprises dissolving the Cd, S and Se in a solvent comprising octadecene and a fatty acid to provide a nanocrystal precursor solution; and heating said precursor solution.

5. The method of claim 1 , wherein the alloy-gradient nanoparticle is homogenous.

6. The method of claim 1 , wherein the alloy-gradient nanoparticle is nonhomogeneous.

7. The method of claim 1 , further comprising the step of coupling an active agent to the aluminum oxide layer.

8. The method of claim 7 , wherein the active agent is associated with the surface of, encapsulated within, surrounded by, or dispersed throughout the passivated semiconductor nanocrystal.

9. The method of claim 7 , wherein the active agent is coupled to the aluminum oxide layer.

10. The method of claim 7 , wherein the active agent is selected from the group consisting of chemotherapeutic agents, diagnostic agents, imaging agents, prophylactic agents, nutraceutical agents, nucleic acids, proteins, peptides, lipids, carbohydrates, hormones, small molecules, metals, ceramics, drugs, vaccines, immunological agents, and combinations thereof.

11. The method of claim 1 , further comprising the step of coupling a targeting moiety to the passivated semiconductor nanocrystal.

12. The method of claim 7 , further comprising the step of coupling a targeting moiety to the active agent.

13. The method as in claim 11 , wherein the targeting moiety is selected from the group consisting of a protein, peptide, antibody, antibody fragment, saccharide, carbohydrate, glycan, cytokine, chemokine, nucleotide, lectin, lipid, receptor, steroid, neurotransmitter, cell surface marker, cancer antigen, glycoprotein antigen, melanoma associated antigen, proteolytic enzyme, angiogenesis marker, prostate membrane specific antigen (PMSA), small cell lung carcinoma antigen (SCLCA), hormone receptor, tumor suppressor gene antigen, cell cycle regulator antigen, proliferation marker, human carcinoma antigen, antigen associated with an immune system disease, antigen associated with a pathogen-borne condition, and combinations thereof.

14. The method as in claim 11 , wherein greater than 20% of the passivated semiconductor nanocrystal surface area is functionalized with the targeting moiety.

15. The method as in claim 11 , wherein greater than 50% of the passivated semiconductor nanocrystal surface area is functionalized with the targeting moiety.

16. The method of claim 1 , further comprising the step of coating said passivated semiconductor nanocrystal with an additional passivation material.

17. The method of claim 1 , further comprising the step of coating said passivated semiconductor nanocrystal with a protective coating.