Process for forming shaped group II-VI semiconductor nanocrystals, and product formed using process
First Claim
1. A process for the formation of Group II-VI semiconductor nanocrystals comprises introducing the precursors into a heated binary mixture of first and second different surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of said semiconductor nanocrystals formed in said binary mixture of surfactants is capable of being controlled by adjusting the ratio of said first and second surfactants in said binary mixture.
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Abstract
A process for the formation of shaped Group II-VI semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.
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Citations
36 Claims
- 1. A process for the formation of Group II-VI semiconductor nanocrystals comprises introducing the precursors into a heated binary mixture of first and second different surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of said semiconductor nanocrystals formed in said binary mixture of surfactants is capable of being controlled by adjusting the ratio of said first and second surfactants in said binary mixture.
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9. A process for forming shaped Group II-VI semiconductor nanocrystals in a heated binary mixture of surfactants which comprises:
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a) forming one or more solutions, each comprising one or more Group II and/or Group VI semiconductor nanocrystal precursors dissolved in a liquid which is a solvent for said one or more semiconductor precursors;
b) forming a binary mixture of high boiling organic surfactants comprising;
i) a first surfactant; and
ii) a second surfactant;
c) adjusting the ratio of said first and second surfactants in said binary mixture to control the shape of said semiconductor nanocrystals to be formed therein;
d) heating said binary mixture of surfactants to a temperature at which said Group II and Group VI precursors will react in said heated binary mixture of surfactants to form said Group II-VI semiconductor nanocrystals;
e) adding said one or more solutions of Group II and Group VI semiconductor nanocrystal precursors to said heated binary mixture of surfactants to form said semiconductor nanocrystals; and
f) subsequently reducing the temperature of said heated binary mixture of surfactants containing said semiconductor nanocrystals to stop said growth of said semiconductor nanocrystals. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
(a) forming a first solution containing at least one Group II metal selected from the group consisting of Zn, Cd, and Hg; and
(b) forming a second solution containing at least one Group VI element selected from the group consisting of S, Se, and Te.
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11. The process of claim 9 wherein said step of forming said one or more solutions, each comprising one or more Group II and Group VI semiconductor nanocrystal precursors dissolved in a liquid which is a solvent for said one or more semiconductor precursors further comprises forming a single solution containing
a) at least one or more Group II metals, or compounds containing Group II metals, selected from the group consisting of Zn, Cd, and Hg; - and
(b) at least one or more Group VI elements, or compounds containing Group VI elements, selected from the group consisting of S, Se, and Te.
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12. The process of claim 9 wherein at least one of said one or more solutions comprises
a) a particular Group II metal; - and
b) a particular Group VI element.
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13. The process of claim 9 wherein:
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a) said heating step is carried out until said binary mixture of surfactants reaches a temperature at which said semiconductor nanocrystals will nucleate when said one or more solutions are added to said binary mixture;
b) said nucleation temperature is lowered to a crystal growth temperature after said step of adding said solution to said heated binary mixture of surfactants; and
c) said heated binary mixture of surfactants containing said one or more solutions is maintained at said crystal growth temperature until said step of reducing the temperature of said mixture containing said solution sufficiently to stop formation of said semiconductor nanocrystals.
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14. The process of claim 9 wherein said concentration of said first surfactant in said binary mixture of surfactants is increased sufficiently to permit growth of substantially spherical semiconductor nanocrystals in said binary mixture of surfactants.
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15. The process of claim 9 wherein said concentration of said second surfactant in said binary mixture of surfactants is increased sufficiently to permit growth of rod-like semiconductor nanocrystals in said binary mixture of surfactants.
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16. The process of claim 9 wherein said heated binary mixture of surfactants comprises two different phosphorus-containing surfactants.
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17. The process of claim 16 wherein said second phosphorus-containing surfactant in said binary mixture of surfactants comprises a phosphorus-containing organic acid.
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18. The process of claim 17 wherein said phosphorus-containing organic acid second surfactant comprises a phosphonic acid surfactant having the formula ROP(OH)2, where R is a 3-18 carbon organic group.
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19. The process of claim 17 wherein said phosphorus-containing organic acid second surfactant is a phosphinic acid having the formula R′
- RxH(1-x)POOH, where R and R′
are the same or different 3-18 carbon organic groups and x is 0-1.
- RxH(1-x)POOH, where R and R′
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20. A process for forming shaped Group II-VI semiconductor nanocrystals in a heated binary mixture of surfactants which comprises:
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a) forming a solution comprising;
i) a first semiconductor precursor comprising one or more particular Group II metals, or compounds containing one or more particular Group II metals;
ii) a second semiconductor precursor comprising one or more particular Group VI elements, or compounds containing one or more particular Group VI elements; and
iii) a liquid which is a solvent for said first and second precursors;
b) forming a binary mixture of high boiling phosphorus-containing organic surfactants comprising;
i) a first surfactant capable of promoting growth of spherical semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants; and
ii) a second surfactant capable of promoting growth of rod-like shaped semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants;
c) adjusting the ratio of said first and second surfactants in said binary mixture to control the shape of said semiconductor nanocrystals to be formed therein;
d) heating said binary mixture of phosphorus-containing organic surfactants to a temperature sufficient to permit formation of Group II-VI semiconductor nanocrystals therein;
e) adding said solution of Group II and Group VI semiconductor nanocrystal precursors to said heated binary mixture of surfactants to form said semiconductor nanocrystals; and
f) subsequently reducing the temperature of said heated binary mixture of surfactants containing said semiconductor nanocrystals to stop said growth of said semiconductor nanocrystals. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
a) said heating step is carried out until said binary mixture of surfactants reaches a temperature at which said semiconductor nanocrystals will nucleate when said one or more solutions are added to said binary mixture;
b) said nucleation temperature is lowered to a crystal growth temperature during or after said step of adding said solution to said heated binary mixture of surfactants; and
c) said heated binary mixture of surfactants containing said one or more solutions is maintained at said crystal growth temperature until said step of reducing the temperature of said mixture containing said solution sufficiently to stop formation of said semiconductor nanocrystals.
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22. The process of claim 21 wherein said nucleation temperature is lowered to a crystal growth temperature during said step of adding said solution of Group II and Group VI semiconductor nanocrystal precursors to said heated binary mixture of surfactants by adding to said binary mixture of surfactants said solution of Group II and Group VI semiconductor nanocrystal precursors at a temperature sufficiently lower than the temperature of said binary surfactant mixture to thereby cool said binary mixture of surfactants down to said crystal growth temperature as said solution of Group II and Group VI semiconductor nanocrystal precursors is added to said heated binary mixture.
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23. The process of claim 20 wherein said Group II metal is selected from the group consisting of Zn, Cd, and Hg;
- and said Group VI element is selected from the group consisting of S, Se, and Te.
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24. The process of claim 20 wherein said liquid which is a solvent for said first and second precursors comprises a polar organic solvent.
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25. The process of claim 23 wherein said solvent comprises a trialkyl phosphine.
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26. The process of claim 20 wherein said first surfactant in said binary mixture of surfactants is selected from the group consisting of a 3-18 carbon tri-alkyl phosphine and a 3-18 carbon tri-alkyl phosphine oxide.
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27. The process of claim 20 wherein said second surfactant in said binary mixture of surfactants comprises a phosphorus-containing organic acid.
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28. The process of claim 27 wherein said phosphorus-containing organic acid second surfactant in said binary mixture comprises phosphonic acid having the formula ROP(OH)2, where R is a 3-18 carbon organic group.
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29. The process of claim 28 wherein said phosphonic acid second surfactant comprises hexyl-phosphonic acid.
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30. The process of claim 27 wherein said phosphorus-containing organic acid second surfactant is a phosphinic acid having the formula R′
- RxH(1-x)POOH, where R and R′
are the same or different 3-18 carbon organic groups and x is 0-1.
- RxH(1-x)POOH, where R and R′
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31. A process for forming shaped CdSe semiconductor nanocrystals in a heated binary mixture of surfactants which comprises:
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a) forming a solution comprising;
i) a first semiconductor precursor comprising Cd metal, and/or one or more compounds containing Cd metal;
ii) a second semiconductor precursor comprising Se, and/or one or more compounds containing Se; and
iii) a liquid which is a solvent for said first and second precursors;
b) forming a binary mixture of high boiling phosphorus-containing organic surfactants comprising;
i) a first phosphorus-containing surfactant capable of promoting growth of spherical semiconductor nanocrystals with increased percentage of said first surfactant in the ratio of said surfactants in said binary mixture of surfactants; and
ii) a second surfactant capable of promoting growth of rod-like shaped semiconductor nanocrystals with increased percentage of said second surfactant in the ratio of said surfactants in said binary mixture of surfactants;
c) adjusting the ratio of said first and second surfactants in said binary mixture to control the shape of said CdSe semiconductor nanocrystals to be formed therein;
d) heating said binary mixture of phosphorus-containing organic surfactants to a temperature sufficient to permit formation of Group II-VI semiconductor nanocrystals therein;
e) adding said solution of Cd and Se semiconductor nanocrystal precursors to said heated binary mixture of surfactants to form said CdSe semiconductor nanocrystals; and
f) subsequently reducing the temperature of said heated binary mixture of surfactants containing said semiconductor nanocrystals to stop said growth of said semiconductor nanocrystals.
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- 32. A rod-like Group II-VI semiconductor nanocrystal formed by reacting together a precursor containing one or more Group II metals selected from the group consisting of Zn, Cd, and Hg with a precursor containing one or more Group VI elements selected from the group consisting of S, Se, and Te in a binary mixture of surfactants which includes an organo phosphorus-containing surfactant capable of promoting growth of rod-like semiconductor nanocrystals when a sufficient amount of said surfactant is present in said binary mixture of surfactants.
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36. A rod shaped CdSe semiconductor nanocrystal formed by reacting together a Cd precursor with a Se precursor in a binary mixture of phosphorus-containing organic surfactants containing at least 5 wt. % of an organo phosphorus-containing acid surfactant.
Specification