Method of semiconductor nanoparticle synthesis
View Patent ↗A method is described for the manufacture of semiconductor nanoparticles. Improved yields are obtained by use of a reducing agent or oxygen reaction promoter.
1. A method of producing nanoparticles comprising.
(a) mixing a first precursor and at least one coordinating solvent to form a first mixture;
(b) exposing the first mixture to a reaction promoter, different from the coordinating solvent, selected from the group consisting of oxygen and a reducing agent, to thereby reduce the first precursor's valency;
(c) heading the first mixture to a temperature that is sufficiently high to of form nanoparticles when a second precursor is added;
(d) introducing a second precursor into the first mixture after the first precursor's valency has been reduced to form a second mixture thereby resulting in the formation of a plurality of nanoparticles; and
(e) cooling the second mixture to stop further growth of the nanoparticles.
2. The method of claim 1 wherein the reaction promoter is a reducing agent.
3. The method of claim 2 wherein the exposing step comprises adding the reducing agent to the first mixture.
4. The method of claim 2 wherein the reducing agent is a chemical reducing agent selected from the group consisting of tertiary, secondary, and primary phosphines; amines; hydrazines; hydroxyphenyl compounds; hydrogen; hydrides; metals; boranes; aldehydes; alcohols; thiols; reducing halides; and polyfunctional reductants.
5. The method of claim 2 wherein the reducing agent is a cathode.
6. The method of claim 5 wherein the cathode is made of a material selected from the group consisting of platinum, silver, and carbon.
7. The method of claim 1 wherein the reaction promoter is oxygen.
8. The method of claim 7 wherein the exposing step comprises directly exposing the first mixture to a source of oxygen.
9. The method of claim 7 wherein the oxygen is formed in situ.
10. The method of claim 9 wherein the oxygen is formed by a redox reaction.
11. The method of claim 10 wherein the exposing step comprises adding a reducing agent selected from the group consisting of tertiary, secondary, and primary phosphines; amines; hydrazines; hydroxyphenyl compounds; hydrogen; hydrides; metals; boranes; aldehydes; alcohols; thiols; reducing halides; and polyfunctional reductants.
12. The method of claim 7 wherein the exposing step comprises exposing a coordinating solvent to a source of oxygen and adding the exposed coordinating solvent to the mixture.
13. The method of claim 1 wherein the coordinating solvent is selected from the group consisting of amines, alkyl phosphines, alkyl phosphine oxides, fatty acids, ethers, furans, phospho-acids, pyridines, alkenes, alkynes and combinations thereof.
14. The method of claim 13 wherein the coordinating solvent is pure.
15. The method of claim 1 wherein the mixing step further includes mixing a ligand with the first precursor and coordinating solvent.
16. The method of claim 15 wherein the ligand is selected from the group consisting of phospho-acids, carboxylic acids, amines, amides, alcohols, ethers, alkenes, and alkynes.
17. The method of claim 16 wherein the ligand is a phosphonic acid.
18. The method of claim 17 wherein the phosphonic acid is selected from the group consisting of hexylphosphonic acid and tetradecylphosphonic acid.
19. The method of claim 1 wherein the coordinating solvent is a mixture of a non-coordinating solvent and a ligand.
20. The method of claim 19 wherein the non-coordinating solvent is an alkane.
21. The method of claim 19 wherein the ligand is selected from the group consisting of phospho-acids, carboxylic acids, amines, amides, alcohols, ethers, alkenes, and alkynes.
22. The method of claim 1 wherein the nanoparticles are semiconductive.
23. The method of claim 22 wherein the first precursor is selected from the group consisting of Group 2, 12, 13 and 14 element-containing compounds.
24. The method of claim 22 wherein the second precursor is selected from the group consisting of Groups 14, 15 and 16 element-containing compounds.
25. The method of claim 1 which further comprises producing a nanoparticle shell.
26. The method of claim 25 wherein the shell producing step comprises:
(a′) mixing the nanoparticles with at least one coordinating solvent to form a third mixture;
(b′) heating the third mixture to a temperature that is sufficiently high to form a shell on the nanoparticles when third and fourth precursors are added;
(c′) introducing third and fourth precursors into the third mixture after heating the third mixture form a fourth mixture thereby resulting in the formation of shells on a plurality of nanoparticles; and
(d′) cooling the third mixture to stop further growth of the shell; wherein the method further comprises exposing the third or fourth mixture to a reaction promoter selected from the group consisting of oxygen and a reducing agent.
27. The method of claim 26 wherein an additive or additive precursor is included in step (a′).
28. A method of producing semiconductive nanoparticles having a valency “n ”, comprising:
(a) mixing a first precursor having a valency “c” and at least one coordinating solvent to form a first mixture;
(b) exposing the first mixture to a reaction promoter different from the coordinating solvent wherein the reaction promoter converts the valency of the first precursor to a valency “a”;
(c) heating the first mixture to a temperature that is sufficiently high to form nanoparticles when a second precursor is added;
(d) introducing a second precursor into the first mixture, the first mixture comprising the first precursor with the valency “a”, to form a second mixture thereby resulting in the formation of a plurality of nanoparticles; wherein the second precursor has a valency “b”, and wherein a+b=n and c+b.≠n; and
(e) cooling the second mixture to stop further growth of the nanoparticles.
29. The method of claim 28 wherein the reaction promoter is a reducing agent.
30. The method of claim 29 wherein the reaction promoter is a cathode.
31. The method of claim 30 wherein the cathode is made of a material selected from the group consisting of platinum, silver and carbon.
32. The method of claim 29 wherein the reducing agent is a chemical reducing agent selected from the group consisting of tertiary, secondary, and primary phosphines; amines; hydrazines; hydroxyphenyl compounds; hydrogen; hydrides; metals; boranes; aldehydes; alcohols; thiols; reducing halides; and polyfunctional reductants.
33. The method of claim 32 wherein the coordinating solvent is pure.
34. The method of claim 28 wherein the reaction promoter is a source of oxygen.
35. The method of claim 28 wherein the reaction promoter is oxygen that is formed in situ by a redox reaction.
36. The method of claim 35 wherein the exposing step comprises adding a reducing agent selected from the group consisting of tertiary, secondary, and primary phosphines; amines; hydrazines; hydroxyphenyl compounds; hydrogen; hydrides; metals; boranes; aldehydes; alcohols; thiols; reducing halides; and polyfunctional reductants.
37. The method of claim 28 wherein the step of heating the first mixture occurs prior to introducing the second precursor.