Methods for synthesis of semiconductor nanocrystals and thermoelectric compositions
View Patent ↗The present invention provides methods for synthesis of IV–VI nanostructures, and thermoelectric compositions formed of such structures. In one aspect, the method includes forming a solution of a Group IV reagent, a Group VI reagent and a surfactant. A reducing agent can be added to the solution, and the resultant solution can be maintained at an elevated temperature, e.g., in a range of about 20° C. to about 360° C., for a duration sufficient for generating nanoparticles as binary alloys of the IV–VI elements.
1. A method of synthesizing nanoparticles, comprising:
forming a solution of a Group IV reagent and Group VI reagent and a surfactant,
adding a reducing agent to the solution, and
maintaining the resultant solution at an elevated temperature in a range of about 20 to about 360° C. for a time duration so as to generate nanoparticles containing said Group IV and Group VI elements.
2. The method of claim 1 , further comprising selecting said surfactant to be any of polyethylene glycol (PEG), hexadecyltrimethylammonium bromide (CTAB) or tergitol NP-9.
3. The method of claim 1 , further comprising selecting said Group IV element to be Pb or Sn.
4. The method of claim 1 , further comprising selecting said Group VI element to be any of Te or Se.
5. The method of claim 1 , further comprising selecting said reagent having a Group IV element to be any of lead acetate, lead chloride, or lead sulfate.
6. The method of claim 1 , further comprising selecting said reagent having a Group VI element to be any of Te powder, Se powder, NaSeO 3 , or NaTeO 3 .
7. The method of claim 1 , further comprising selecting said reducing agent to be any of a hydrazine hydrate, sodium borohydride (NaBH 4 ).
8. The method of claim 1 , further comprising selecting said time duration to be in a range of about 1 hour to about 50 hours.
9. The method of claim 1 , further comprising adding a base to said solution so as to facilitate reaction of said reagents for generating said nanoparticles.
10. The method of claim 9 , further comprising selecting said base to be any of NaOH.
11. The method of claim 1 , further comprising selecting said solvent to be any of water, alcohol and hexane.
12. The method of claim 1 , further comprising centrifuging a product generated subsequent to the step of maintaining the solution at an elevated temperature to collect a precipitate containing the nanoparticles.
13. The method of claim 12 , further comprising washing said precipitate to remove byproducts from the generated nanoparticles.
14. The method of claim 1 , further comprising selecting said surfactant and its concentration such that said resultant nanoparticles have sizes in a range of about a few nanometers to about 200 nanometers.
15. The method of claim 14 , further comprising selecting a molar concentration of said surfactant in the solution to be in a range of about 0.001 to about 0.1.
16. The method of claim 1 , further comprising compactifying said nanoparticles by applying a pressure in a range of about 100 to about 1000 MPa thereto at a temperature in a range of about 400 C. to about 900 C.
17. A method of generating PbTe nanoparticles, comprising
preparing a solution containing a surfactant, a Pb-containing reagent and a Te-containing reagent,
adding a reducing agent to said solution,
maintaining the resultant solution at a temperature in a range of about 20° C. to about 360° C. for a time duration in a range of about 1 hour to about 50 hours so as to generate a reaction product containing PbTe nanoparticles.
18. The method of claim 17 , further comprising washing said product to strip off byproducts from said nanoparticles.
19. The method of claim 17 , further comprising selecting said solvent to be water.
20. The method of claim 17 , further comprising selecting said reducing agent to be hydrazine hydrate.
21. The method of claim 17 , wherein said Pb-containing reagent comprises a lead-containing salt.
22. The method of claim 21 , wherein said Pb-containing salt comprises any of lead acetate, lead chloride and lead sulfate.
23. The method of claim 17 , wherein said Te-containing reagent comprises any of Te powder, NaTeO 3 .
24. The method of claim 17 , further comprising adding a base to said solution so as to facilitate formation of the nanoparticles.
25. The method of claim 24 , further comprising selecting said base to be NaOH.
26. The method of claim 17 , further comprising selecting a molar concentration of said surfactant so as to generate PbTe nanoparticles having average sizes in a range of about a few nanometers to about 200 nanometers.
27. A method of forming PbSe nanoparticles, comprising
preparing a solution containing a surfactant, and Se-containing reagent and a Pb-containing reagent,
adding a reducing agent and a base to the solution,
maintaining the resultant solution at a temperature below about 360° C. for a time duration sufficient to cause formation of a product containing PbSe nanoparticles.
28. The method of claim 27 , further comprising selecting said surfactant to be any of PEG, CTAB and tergitol NP-9.
29. The method of claim 27 , further comprising selecting said Se-containing reagent to be any of Se powder or an Se salt.
30. The method of claim 29 , further comprising selecting said Se salt to be NaSeO 3 .
31. The method of claim 27 , further comprising selecting said lead-containing reagent to be a lead-containing salt.
32. The method of claim 31 , wherein said lead-containing salt comprises lead acetate.
33. The method of claim 27 , further comprising selecting said reaction temperature to be in a range of about 20° C. to about 360° C.