One-pot synthesis of highly luminescent InP/ZnS nanocrystals without ...
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One-pot synthesis of highly luminescent InP/ZnS nanocrystals without precursor injection Liang Li and Peter Reiss*
CEA Grenoble, INAC/SPrAM (UMR 5819 CEA-CNRS-UJF), 17 rue des Martyrs, 38054 Grenoble cedex 9, France. E-mail: [email protected]
Materials: Except for zinc stearate (90%, Riedel de Haën), all reagents and solvents were purchased from Sigma-Aldrich and used as received: indium acetate (99.99%), myristic acid (>99%), tris(trimethylsilyl)phosphine (95%), 1-dodecanethiol (97%), 1-octadecene (90%). Synthesis of InP/ZnS core/shell nanocrystals: For a typical synthesis, 0.1 mmol of indium myristate, prepared from indium acetate and myristic acid (MA), 0.1 mmol of zinc stearate, 0.1 mmol of dodecanethiol (DDT), 0.1 mmol of tris(trimethylsilyl)phosphine (P(TMS)3) and 8 mL of 1-octadecene (ODE) were stirred under inert atmosphere in a three-neck flask equipped with a condenser. The mixture was then heated to a temperature within 230°C~300°C using a rate of 2°C/s and kept for a certain time (5 min – 2 hrs) to grow the InP/ZnS NCs. During the temperature increase, a color change from colorless to green was observed at 60-80°C, indicating that P(TMS)3 started to react with the indium precursor. To isolate the NCs, the reaction mixture was cooled down to room temperature, and 1 volume equivalent of a chloroform/methanol (1:1 vol:vol) mixture as well as 10 equivalents of acetone were added, followed by centrifugation. The resulting precipitate could readily be dispersed in a number of organic solvents, including hexanes, toluene or chloroform. No size sorting procedures were performed for any of the samples presented here. Preparation of indium myristate In(MA)x: 2 mmol of indium acetate were mixed under inert atmosphere with the desired quantity (i.e. 4-8 mmol) of myristic acid (MA) and 20 mL of ODE in a 50 mL three neck flask equipped with a condenser. The mixture was heated to 100-120°C for 1 h under vacuum to obtain an optically clear solution, backfilled with Ar, and then cooled down to room temperature. Stock solutions with different In:MA ratios were prepared and stored in a glovebox. Measurement of the fluorescence quantum yield (Q.Y.):1 The absolute fluorescence Q.Y.s of the InP/ZnS NCs were determined by comparison with a standard of known Q.Y. (freshly prepared solution of Rhodamine 6G in ethanol; Q.Y. 95%), using the following formula: ΦNC = ΦStandard (gradNC/gradStandard)(nNC2/nStandard2) with Φ being the Q.Y., grad the gradient (slope) of the plot of the integrated fluorescence intensity vs. absorbance and n the refractive index of the solvent (1.375 for hexane, 1.36 for ethanol). Purified samples of InP/ZnS in hexane were put into 1 cm quartz cuvettes and diluted until the absorbance at the first excitonic was below 0.1. At least three samples of different concentration were prepared. The absorbance of the standard was adjusted to be equal to each NC dispersion at the excitation wavelength (450 nm).
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a)
b)
c)
Figure S1. Representative EDX spectra (JEOL JSM-840A SEM equipped with an Oxford Instruments energy dispersive X-ray analyzer) of samples with different shell thickness: a) In:P:MA:Zn:S = 1:1:2:1:1, 60 min; b) In:P:MA:Zn:S = 1:1:2:5:5, 60 min (in this case 4 equivalents of the Zn and S precursors have been added after 30 min of reaction). c) Temporal evolution of the composition of sample a (dashed lines are added to guide the eye).
Table S1. Atomic % of the elements determined from EDX analysis (mean values of 10 independent measurements per sample) for aliquots taken at different reaction times (In:P:MA:Zn:S = 1:1:2:1:1; values in brackets at 60 min: In:P:MA:Zn:S = 1:1:2:5:5 [sample b in Fig. S1]).
t(min) 5 10 30 60
P 25.04 22.73 19.63 19.08 (5.62)
In 36.30 36.73 36.77 34.05 (8.82)
Zn 11.60 16.00 19.06 19.99 (30.83)
S 27.06 24.54 24.53 26.89 (54.71)
S2
Figure S2. Evolution of the UV-vis absorption spectra with reaction time at different temperatures and at varying ratios of In:MA (m=minutes). Within each panel the spectra have been vertically shifted for clarity. (In:P: Zn:S = 1:1:1:1)
Figure S3. TEM images of InP/ZnS NCs. Left/middle: average size 3.5 nm (In:P:MA:Zn:S = 1:0.7:3.5:1:1); right: 4.1 nm (In:P:MA:Zn:S = 1:1:2:1:1).
Figure S4. Influence of the ZnS precursor concentration on the growth of InP/ZnS NCs obtained at 270°C after a reaction time of 120 min.
References (1) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, 991-1024.
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One-pot synthesis of highly luminescent InP/ZnS nanocrystals without precursor injection Liang Li and Peter Reiss*
CEA Grenoble, INAC/SPrAM (UMR 5819 CEA-CNRS-UJF), 17 rue des Martyrs, 38054 Grenoble cedex 9, France. E-mail: [email protected]
Materials: Except for zinc stearate (90%, Riedel de Haën), all reagents and solvents were purchased from Sigma-Aldrich and used as received: indium acetate (99.99%), myristic acid (>99%), tris(trimethylsilyl)phosphine (95%), 1-dodecanethiol (97%), 1-octadecene (90%). Synthesis of InP/ZnS core/shell nanocrystals: For a typical synthesis, 0.1 mmol of indium myristate, prepared from indium acetate and myristic acid (MA), 0.1 mmol of zinc stearate, 0.1 mmol of dodecanethiol (DDT), 0.1 mmol of tris(trimethylsilyl)phosphine (P(TMS)3) and 8 mL of 1-octadecene (ODE) were stirred under inert atmosphere in a three-neck flask equipped with a condenser. The mixture was then heated to a temperature within 230°C~300°C using a rate of 2°C/s and kept for a certain time (5 min – 2 hrs) to grow the InP/ZnS NCs. During the temperature increase, a color change from colorless to green was observed at 60-80°C, indicating that P(TMS)3 started to react with the indium precursor. To isolate the NCs, the reaction mixture was cooled down to room temperature, and 1 volume equivalent of a chloroform/methanol (1:1 vol:vol) mixture as well as 10 equivalents of acetone were added, followed by centrifugation. The resulting precipitate could readily be dispersed in a number of organic solvents, including hexanes, toluene or chloroform. No size sorting procedures were performed for any of the samples presented here. Preparation of indium myristate In(MA)x: 2 mmol of indium acetate were mixed under inert atmosphere with the desired quantity (i.e. 4-8 mmol) of myristic acid (MA) and 20 mL of ODE in a 50 mL three neck flask equipped with a condenser. The mixture was heated to 100-120°C for 1 h under vacuum to obtain an optically clear solution, backfilled with Ar, and then cooled down to room temperature. Stock solutions with different In:MA ratios were prepared and stored in a glovebox. Measurement of the fluorescence quantum yield (Q.Y.):1 The absolute fluorescence Q.Y.s of the InP/ZnS NCs were determined by comparison with a standard of known Q.Y. (freshly prepared solution of Rhodamine 6G in ethanol; Q.Y. 95%), using the following formula: ΦNC = ΦStandard (gradNC/gradStandard)(nNC2/nStandard2) with Φ being the Q.Y., grad the gradient (slope) of the plot of the integrated fluorescence intensity vs. absorbance and n the refractive index of the solvent (1.375 for hexane, 1.36 for ethanol). Purified samples of InP/ZnS in hexane were put into 1 cm quartz cuvettes and diluted until the absorbance at the first excitonic was below 0.1. At least three samples of different concentration were prepared. The absorbance of the standard was adjusted to be equal to each NC dispersion at the excitation wavelength (450 nm).
S1
a)
b)
c)
Figure S1. Representative EDX spectra (JEOL JSM-840A SEM equipped with an Oxford Instruments energy dispersive X-ray analyzer) of samples with different shell thickness: a) In:P:MA:Zn:S = 1:1:2:1:1, 60 min; b) In:P:MA:Zn:S = 1:1:2:5:5, 60 min (in this case 4 equivalents of the Zn and S precursors have been added after 30 min of reaction). c) Temporal evolution of the composition of sample a (dashed lines are added to guide the eye).
Table S1. Atomic % of the elements determined from EDX analysis (mean values of 10 independent measurements per sample) for aliquots taken at different reaction times (In:P:MA:Zn:S = 1:1:2:1:1; values in brackets at 60 min: In:P:MA:Zn:S = 1:1:2:5:5 [sample b in Fig. S1]).
t(min) 5 10 30 60
P 25.04 22.73 19.63 19.08 (5.62)
In 36.30 36.73 36.77 34.05 (8.82)
Zn 11.60 16.00 19.06 19.99 (30.83)
S 27.06 24.54 24.53 26.89 (54.71)
S2
Figure S2. Evolution of the UV-vis absorption spectra with reaction time at different temperatures and at varying ratios of In:MA (m=minutes). Within each panel the spectra have been vertically shifted for clarity. (In:P: Zn:S = 1:1:1:1)
Figure S3. TEM images of InP/ZnS NCs. Left/middle: average size 3.5 nm (In:P:MA:Zn:S = 1:0.7:3.5:1:1); right: 4.1 nm (In:P:MA:Zn:S = 1:1:2:1:1).
Figure S4. Influence of the ZnS precursor concentration on the growth of InP/ZnS NCs obtained at 270°C after a reaction time of 120 min.
References (1) Demas, J. N.; Crosby, G. A. J. Phys. Chem. 1971, 75, 991-1024.
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