Preparation of nanoparticle materials

Abstract

A method of producing nanoparticles comprises effecting conversion of a nanoparticle precursor composition to the material of the nanoparticles. The nanoparticle precursor composition comprises a first precursor species containing a group 13 element to be incorporated into the nanoparticles and a separate second precursor species containing either a group 15 or a group 16 element to be incorporated into the nanoparticles. The conversion is effected in the presence of molecular cluster compounds under conditions permitting seeding and growth of the nanoparticles on the molecular cluster compounds. The molecular cluster compounds and nanoparticle precursor composition can be dissolved in a solvent at a first temperature to form a solution and the temperature of the solution can then be increased to a second temperature sufficient to initiate seeding and growth of the nanoparticles on the molecular cluster compounds.

Claims

1. A method of producing nanoparticles comprising: effecting conversion of a nanoparticle precursor composition to a material of the nanoparticles, said precursor composition comprising a first precursor species containing a group 13 element to be incorporated into the nanoparticles and a separate second precursor species containing either a group 15 or a group 16 element to be incorporated into the nanoparticles, wherein said conversion is effected in the presence of molecular cluster compounds under conditions permitting seeding and growth of the nanoparticles on the molecular cluster compounds.

2. The method of claim 1, wherein the Group 13 element is indium (In) and the Group 15 element is phosphorus (P).

3. The method of claim 1, wherein the Group 13 element is indium (In) and the Group 16 element is sulfur (S).

4. The method of claim 1, wherein the Group 13 element is indium (In) and the Group 16 element is selenium (Se).

5. The method of claim 1, wherein the first precursor species comprises a group 13 element and a carboxylate.

6. The method of claim 5, wherein the carboxylate is acetate.

7. The method of claim 5, wherein the carboxylate is stearate.

8. The method of claim 1, wherein the second precursor species comprises PH.sub.3.

9. The method of claim 1, wherein the second precursor species comprises a group 15 element and a trimethylsilyl group.

10. The method of claim 1, wherein said conversion effected in the presence of a molecular cluster compound under conditions permitting seeding and growth of quaternary or ternary nanoparticles on the molecular cluster compounds.

11. A method of producing nanoparticles comprising: effecting conversion of a of a nanoparticle precursor composition to a material of the nanoparticles, said precursor composition comprising a first precursor species containing a group 13 element to be incorporated into the nanoparticles and a separate second precursor species containing either a group 15 or a group 16 element to be incorporated into the nanoparticles, wherein said conversion is effected in the presence of molecular cluster compounds under conditions permitting seeding and growth of the nanoparticles on the molecular cluster compounds, and wherein the molecular cluster compounds and nanoparticle precursor composition are dissolved in a solvent at a first temperature to form a solution and the temperature of the solution is then increased to a second temperature which is sufficient to initiate seeding and growth of the nanoparticles on the molecular cluster compounds.

12. The method of claim 11, wherein the Group 13 element is indium (In) and the Group 15 element is phosphorus (P).

13. The method of claim 11, wherein the Group 13 element is indium (In) and the Group 16 element is sulfur (S).

14. The method of claim 11, wherein the Group 13 element is indium (In) and the Group 16 element is selenium (Se).

15. The method of claim 11, wherein the first precursor species comprises a group 13 element and a carboxylate.

16. The method of claim 15, wherein the carboxylate is acetate.

17. The method of claim 15, wherein the carboxylate is stearate.

18. The method of claim 11, wherein the second precursor species comprises PH.sub.3.

19. The method of claim 11, wherein the second precursor species comprises a group 15 element and a trimethylsilyl group.

20. The method of claim 11, wherein said conversion effected in the presence of a molecular cluster compound under conditions permitting seeding and growth of quaternary or ternary nanoparticles on the molecular cluster compounds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is illustrated with reference to the following non-limiting Examples and accompanying figures, in which:

(2) FIG. 1) is a diagram of a) core particle consisting of a CdSe core and HDA as an organic capping agent, b) core-shell particle consisting of a CdSe core a ZnS shell and HDA as an organic capping agent, c) core-multi shell organic capped particle consisting of a CdSe core a HgS shell followed by a ZnS shell with a HDA capping agent;

(3) FIG. 2) Molecular clusters used as seeding agents: a) Zn.sub.10(SEt).sub.10Et.sub.10; b) [RGaS].sub.4; c) [Bu.sup.tGaS].sub.7; d) [RInSe].sub.4; and e) [X].sub.4[M.sub.10Se.sub.4(SPh).sub.16]X=cation, M=Zn, Cd, Te;

(4) FIGS. 3A and 3B depict the formation of a Cadmium selenide quantum dot using [M.sub.10Se.sub.4(SPh).sub.16][X].sub.4 XLi.sup.+or (CH.sub.3).sub.3NH.sup.+, Et.sub.3NH.sup.+ as the molecular seed and cadmium acetate and tri-noctylphosphine selenide as the cadmium and selenium element-source precursors and with hexadecylamine used as the capping agent;

(5) FIGS. 4A and 4B depict the formation of a gallium sulfide quantum dot using [.sup.tBuGaS].sub.7 as the molecular seed and gallium(II)acetylacetonate and tri-n-octylphosphine sulfide as the gallium and sulfide element-source precursors and with hexadecylamine used as the capping agent;

(6) FIGS. 5A and 5B depict the formation of a indium selenide quantum dot using as the molecular seed and Indium(II)acetylacetonate and tri-n-octylphosphine sulfide as the Indium and selenide element-source precursors and with hexadecylamine and tri-n-octylphosphine oxide used as the capping agent;

(7) FIGS. 6A and 6B depict the formation of a zinc sulfide quantum dot using Zn.sub.10(SEt).sub.10Et.sub.10 as the molecular seed and zinc acetate and tri-n-octylphosphine sulfide as the zinc and sulfur element-source precursors and with hexadecylamine used as the capping agent;

(8) FIG. 7) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/Cd(CH.sub.3CO.sub.2).sub.2 in HDA in accordance with Example 2;

(9) FIG. 8) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/Cd(CH.sub.3CO.sub.2).sub.2 in HDA in accordance with Example 1;

(10) FIG. 9) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOP/Se/CdO in HDA in accordance with Example 3;

(11) FIG. 10) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/Cd(OH).sub.2 in HDA in accordance with Example 4;

(12) FIG. 11) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/Me.sub.2Cd in HDA in accordance with Example 5;

(13) FIG. 12) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/(C.sub.17H.sub.35COO).sub.2Cd in HDA in accordance with Example 7;

(14) FIG. 13) Evolution of the PL spectra of CdSe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/TOPSe/CdCO.sub.3 in HDA in accordance with Example 8; and

(15) FIG. 14) Evolution of the PL spectra of CdTe nanoparticles as the nanoparticles become bigger during growth. Preparation from [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]/Te as a slurry in TOP/Cd(CH.sub.3CO.sub.2).sub.2 in HDA in accordance with Example 9.

EXAMPLES

(16) All syntheses and manipulations were carried out under a dry oxygen-free argon or nitrogen atmosphere using standard Schlenk or glove box techniques. All solvents were distilled from appropriate drying agents prior to use (Na/K-benzophenone for THF, Et.sub.2O, toluene, hexanes and pentane). HDA, octylamine, TOP, Cd(CH.sub.3CO.sub.2).sub.2, selenium powder, CdO, CdCO.sub.3 (Aldrich) were procured commercially and used without further purification.

(17) UV-vis absorption spectra were measured on a Heios Thermospectronic. Photoluminescence (PL) spectra were measured with a Fluorolog-3 (FL3-22) photo spectrometer at the excitation wavelength 380 nm. Powder X-Ray diffraction (PXRD) measurements were performed on a Bruker AXS D8 diffractometer using monochromated CuK.sub. radiation.

(18) For all methods all capping agent solutions were dried and degassed before use by heating the mixture to 120 C. under a dynamic vacuum for at least 1 hour. The reaction mixture was then cooled to the desired temperature for that particular reaction before any seeding agent or growth precursors were added to the solution.

(19) Cluster Preparation

(20) Preparation of [HNEt.sub.3].sub.2[Cd.sub.4(SPh).sub.10]

(21) To a stirred methanol (60 ml) solution of benzenethiol (20.00 g, 182 mmol) and triethylamine (18.50 g, 182 mmoL) was added dropwise Cd(NO.sub.3).sub.24H.sub.2O (21.00 g, 68.00 mmol) that had previously been dissolved in methanol (60 mL). The solution was then allowed to stir while warming until the precipitate had completely dissolved to leave a clear solution. This was then place at 5 C. for 24 h in which time large colourless crystals of [HNEt.sub.3].sub.2[Cd.sub.4(SPh).sub.10] had formed. FW=1745.85. Anal. Calcu for C.sub.72H.sub.82N.sub.2S.sub.10Cd.sub.4 C=49.53, H=4.70, N=1.61, S=18.37, Cd=25.75%; Found C=49.73, H=4.88, N=1.59, S=17.92%

(22) Preparation of [HNEt.sub.3].sub.4[Cd.sub.10(SPh).sub.16]

(23) This was by a similar procedure to that described by Dance et al.sup.36. To a stirred acetonitrile (100 ml) solution of [HNEt.sub.3].sub.2[Cd.sub.4(SPh).sub.10] (80.00 g, 45.58 mmol) was added 3.57 g 45.21 mmol of selenium powder, the resulting slurry was left to stir for 12 hours, this produced a white precipitate. A further 750 ml of acetonitrile was added and the solution warmed to 75 C. to give a clear pale yellow solution which was allowed to cool to 5 C., yielding large colourless crystals. The crystals were washed in hexane and recrystallized from hot acetonitrile. To give 22.50 g of [HNEt.sub.3].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16]. FW=3595.19 Anal. Calc for C.sub.120H.sub.144N.sub.4Se.sub.4S.sub.16Cd.sub.10. C=40.08, H=4.00, N=1.56, S=14.27, Se=8.78, Cd=31.26%. Found C=40.04, H=4.03, N=1.48, S=14.22, Cd=31.20%.

Example 1

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/Cd(CH3CO2)2 in HDA

(24) HDA (300 g) was placed in a three-neck flask and dried/degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 1.0 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.311 mmol), TOPSe (20 ml, 40.00 mmol) [previously prepared from dissolving selenium powder in TOP] and Cd(CH.sub.3CO.sub.2).sub.2 (10.66 g 40.00 mmol) the temperature of reaction mixture was gradually increased from 70 C. to 180 C. over an 8 hour period. The progressive formation/growth of the nanoparticles was monitored by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached 572 nm by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol which gave a precipitation of nanoparticles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA and Cd(CH.sub.3CO.sub.2).sub.2. This produced 9.26 g of HDA capped CdSe nanoparticles.

Example 2

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/Cd(CH3CO2)2 in HDA

(25) HDA (250 g) and octylamine (20 g) was placed in a three-neck flask and dried/degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 1.0 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.311 mmol), TOPSe (1M, 4 ml, 4.00 mmol) [previously prepared from dissolving selenium powder in TOP] and Cd(CH.sub.3CO.sub.2).sub.2 dissolved in TOP (0.5M, 4 ml, 2.00 mmol) the temperature of reaction mixture was gradually increased from 70 C. to 150 C. over an hour period. A further 17 ml (17.00 mmol) of TOPSe and 27 ml of a 0.5M Cd(CH.sub.3CO.sub.2).sub.2 dissolved in TOP (13.50 mmol) were added dropwise while the temperature was gradually increased to 200 C. over a 24 hour period. The progressive formation/growth of the nanoparticles was monitored by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size 630 nm by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol which gave a precipitation of particles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 4.56 g of HDA capped CdSe nanoparticles.

Example 3

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOP/Se/CdO in HDA

(26) HDA (150 g) and t-decylphosphonic acid (0.75 g) was placed in a three-neck flask and dried and degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 80 C. To this was added 0.5 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.156 mmol), 20 ml of TOP, 0.6 g of selenium powder (7.599 mmol) and 0.8 g CdO (6.231 mmol) the reaction mixture was allowed to stir to give a pale red cloudy mixture. The temperature of the reaction mixture was gradually increased from 80 C. to 250 C. over a period of 24 h. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (593 nm) by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol, which gave a precipitation of particles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 1.55 g of HDA capped CdSe nanoparticles.

Example 4

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/Cd(HO)2 in HDA

(27) HDA (400 g) was placed in a three-neck flask and dried and degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 1.00 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.278 mmol), 20.0 ml of TOPSe, (2M solution) and 5.85 g of Cd(OH).sub.2 (40.00 mmol), the reaction mixture was allowed to stir to give a pale yellow cloudy mixture. The temperature of the reaction mixture was gradually increased from 70 C. to 240 C. over a period of 24 h. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (609 nm) by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol, which gave a precipitation of particles. The resulting CdSe were dried before redissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 10.18 g of HDA capped CdSe nanoparticles.

Example 5

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/Me2Cd in HDA

(28) HDA (100 g) was placed in a three-neck flask and dried and degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 0.13 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.036 mmol), 2.5 ml of TOPSe, (2M solution) and 0.71 g Me.sub.2Cd [that had previously been dissolved in TOP] (0.358 ml, 5.00 mmol) the reaction mixture was allowed to stir. The temperature of the reaction mixture was gradually increased from 80 C. to 260 C. over a period of 24 h. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-Vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (587 nm) by cooling the reaction to 60 C. followed by addition of 100 ml of dry warm ethanol, which gave a precipitation of particles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 1.52 g of HDA capped CdSe nanoparticles.

Example 6

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/Me2Cd in HDA

(29) HDA (100 g) was placed in a three-neck flask and dried and degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 0.13 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.036 mmol). The temperature was then increased to 100 C. and maintained at this temperature while 2.5 ml of TOPSe, (2M solution) and 0.71 g Me.sub.2Cd [that had previously been dissolved in TOP] (0.358 ml, 5.00 mmol) were added dropwise over a 4 hour period. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV Vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (500 nm) by cooling the reaction to 60 C. followed by addition of 100 ml of dry warm ethanol, which gave a precipitation of particles. The resulting CdSe were dried before redissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 1.26 g of HDA capped CdSe nanoparticles.

Example 7

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/(C17H35COO)2Cd in HDA

(30) HDA (200 g) was placed in a three-neck flask and dried and degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 80 C. To this was added 0.5 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.139 mmol), 20 ml of TOPSe (2M solution) and a solution of 2.568 g CdO (20 mmol) previously dissolved in steric acid (23.00 g), the reaction mixture was allowed to stir to give a pale yellow clear solution. The temperature of the reaction mixture was gradually increased from 70 C. to 220 C. over a period of 24 h. The progressive formation/growth of the nanoparticles was followed by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (590 nm) by cooling the reaction to 60 C. followed by addition of 400 ml of dry warm ethanol, which gave a precipitation of particles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 4.27 g of HDA capped CdSe nanoparticles.

Example 8

Preparation of CdSe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPSe/CdCO3 in HDA

(31) HDA (50 g) was placed in a three-neck flask and dried/degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 75 C. To this was added 0.5 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.156 mmol), TOPSe (1.0M, 5 ml, 5.00 mmol) [previously prepared from dissolving selenium powder in TOP] and CdCO.sub.3 dissolved in TOP (0.5M, 5 ml, 2.50 mmol) the temperature of reaction mixture was gradually increased from 70 C. to 200 C. over a 48 h period. The progressive formation/growth of the nanoparticles were monitored by their emission wavelength by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached the desired size (587 nm) by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol which gave a precipitation of particles. The resulting CdSe were dried before re-dissolving in toluene filtering through Celite followed by reprecipitation from warm ethanol to remove any excess HDA. This produced 0.95 g of HDA capped CdSe nanoparticles.

Example 9

Preparation of CdTe Nanoparticles from [Et3NH]4[Cd10Se4(SPh)16]/TOPTe/Cd(Ch3CO2)2 in HDA

(32) HDA (200 g) was placed in a three-neck flask and dried/degassed by heating to 120 C. under a dynamic vacuum for 1 hour. The solution was then cooled to 70 C. To this was added 1.0 g of [Et.sub.3NH].sub.4[Cd.sub.10Se.sub.4(SPh).sub.16] (0.311 mmol), a brown slurry of TOP (20 ml) with tellurium (2.55 g, 20.00 mmol) along with Cd(CH.sub.3CO.sub.2).sub.2 (4.33 g, 20.00 mmol) was added. The temperature of reaction mixture was gradually increased from 70 C. to 160 C. over an 8 hour period. The progressive formation/growth on the CdTe nanoparticles was monitored by their emission wavelengths by taking aliquots from the reaction mixture and measuring their UV-vis and PL spectra. The reaction was stopped when the emission spectra had reached (624 nm) by cooling the reaction to 60 C. followed by addition of 200 ml of dry warm ethanol which gave a precipitation of particles. The resulting CdTe were dried before recrystallizing from toluene followed by re-precipitation from warm ethanol to remove any excess HDA. This produced 6.92 g of HDA capped CdTe nanoparticles.

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