Synthesis of Oxide-Free InP QDs: Surface Control and H 2 - Assisted Growth

Transcription

1 Supporting Information Synthesis of Oxide-Free InP QDs: Surface Control and H 2 - Assisted Growth Edwin A. Baquero, a,b Héloïse Virieux, a Robert A. Swain, a Angélique Gillet, a Arnaud Cros-Gagneux, a Yannick Coppel, c Bruno Chaudret, a Céline Nayral,* a and Fabien Delpech* a a Université de Toulouse; INSA, UPS, CNRS; LPCNO (Laboratoire de Physique et Chimie des Nano- Objets), 135 avenue de Rangueil, F Toulouse, France. b Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia Sede Bogotá, Carrera 30 No , Bogotá, Colombia c Laboratoire de Chimie de Coordination, UPR-CNRS 8241, 205 route de Narbonne, Toulouse Cedex, France cnayral@insa-toulouse.fr, fdelpech@insa-toulouse.fr Table of Contents 1. Experimental Procedures S2 2. Analysis of InP QDs S5 3. Solid State NMR analysis of InP QDs S7 4. TEM Images of Growing Experiments S13 5. Analysis of InP@ZnS QDs S14 6. References S16 S1

2 1. Experimental Procedures Materials: Hexadecylamine (HDA 98%), palmitic acid (PA, 99%), oleylamine (OLA, 85%), tris(trimethylsilyl)phosphine (PTMS, 98.0 %), and trioctylphosphine (TOP, 99%) were purchased from Strem. Tris(N,N -diisopropylacetamidinato) Indium(III) was purchased from Nanomeps. Ethanol and mesitylene (RPE, Analysis grade) were purchased from Carlo Erba. Zinc stearate 99%, and sulfur powder 99% were purchased from sigma Aldrich. All reagents and solvents were dried, distilled and degassed before use. All manipulations were carried out under argon atmosphere using Schlenk tubes and vacuum line techniques, or in glovebox. Synthesis of InP QDs: mg ( mmol) of tris(n,n -diisopropylacetamidinato) Indium(III), mg ( mmol) of palmitic acid, and 72.4 mg (0.300 mmol) of HDA were dissolved in 3 ml of mesitylene in a 100 ml Fischer Porter. Then, 2 ml of a (TMS) 3 P solution (0.075 M in mesitylene) was injected at room temperature. After injection, the system was closed and stirred at 150 C (for sample 1) or 230 C under either Argon (for sample 2) or H 2 or D 2 at 1.8 bar relative to atmospheric pressure (for samples 3 and 4, respectively) for 21h in a Fischer Porter flask. During that time, the color of the solution changed from pale yellow to dark red (for samples 1 and 2) or dark brown (for sample 3). Then, the reaction was allowed to reach room temperature. The InP QDs were precipitated by addition of 3 x 15 ml of EtOH, centrifuged at rpm during 12 min, and dry under vacuum during 5h. Synthesis of InP@ZnS QDs: This protocol was adapted to one already reported 1 as follows: an InP QDs synthesis is performed as described above. Instead of making purification by precipitation, the system was cooling down at room temperature, then, inside the glovebox, the solution was transferred to a three-neck flask and 5 ml of oleylamine (OLA) is added. Then, outside the glovebox, the system is heated up at 190 C, and slow injection of 5 eq (1.88 ml, mmol) of zinc stearate M in 1- octadecene (ODE) is performed. After 30 minutes, 5 eq (0.34 ml, 0.75 mmol) of saturated solution of sulfur in trioctylphosphine (TOP-S, 2.20 M) is slowly injected and stirred at 200 C during 90 minutes. Then, 3.5 eq (1.31 ml, mmol) of solution of zinc stearate (0.400 M) is added and the system is heated up at 230 C for 30 minutes. After, 3.5 eq (0.24 ml, 0.52 mmol) of TOP-S (2.20 M) is slowly injected and the system is then heated up at 260 C during 30 minutes. Finally, 1.75 eq (0.66 ml, 0.26 mmol) of zinc stearate (0.400 M) is added to the system and heated up at the same temperature during 30 minutes more. The total time of reaction is 210 minutes. At the end of the reaction, the temperature S2

3 is cooled down. quantum dots are then purified three times by precipitating them in ethanol, centrifuged at rpm during 10 minutes and suspended in toluene. Growth of InP QDs: Once the InP QDs 2 or 3 were obtained following the procedure above mentioned, the Fischer-Porter flask was introduced in the glove-box and then, one third of the initial amount of each reagent was added: 53.9 mg (0.100 mmol) of tris(n,n -diisopropylacetamidinato) Indium(III), 77.5 mg (0.300 mmol) of palmitic acid, and 24.1 mg (0.100 mmol) of HDA dissolved in 1 ml of mesitylene and then, 0.67 ml of a (TMS) 3 P solution (0.075 M in mesitylene) was injected at room temperature. After injection, the system was closed and stirred at 230 C under either Argon (growth for sample 2) or H 2 at 1.8 bar relative to atmospheric pressure (growth for sample 3) for 21h. Then, the reaction was allowed to reach room temperature, and then the same procedure of addition was repeated for samples 2 (4 times) and 3 (7 times). Once the additions have been completed, the InP QDs were precipitated by addition of 3 x 15 ml of EtOH, centrifuged at rpm during 12 min, and dry under vacuum during 5h. Samples Characterization Solid-state NMR experiments were recorded on a Bruker AvanceIII 400 spectrometer. Samples were packed into 3.2mm zirconia rotors inside a glove box. The rotors were spun between 8 to 18 khz at room temperature. For 1 H MAS and 13 C DP (direct polarization) MAS experiments, small flip angle (~30 ) were used with recycle delays of 5 s and 10 s, respectively. 31 P Hahn-echo and 2 H solid-echo MAS were performed with a recycle delay of 60 s and 6 s, respectively. 13 C CP-MAS, 31 P CP-MAS and 2 H CP-MAS spectra were recorded with a recycle delay of 2 s and contact times of 2 ms, 2 ms and 3 ms, respectively. All chemical shifts for 1 H and 13 C are relative to TMS. 31 P chemical shifts were referenced to an external 85% H 3 PO 4 sample. 2 H MAS NMR spectra were simulated with the Dmfit software. 2 Samples for TEM analysis were prepared in glovebox by slow evaporation of a drop of the colloidal solution deposited onto a carbon-covered copper grid. TEM analysis were performed at the Service Commun de Microscopie Electronique de l Université Paul Sabatier (TEMSCAN) on a JEOL JEM 1400 electron microscope operating at 100kV with a point resolution of 4.5 Å. The size distributions were determined by measuring at least 250 particles using image J software. S3

4 X-ray diffraction spectra were recorded on a MPD Pro Panalytical spectrometer using the Cu Kα radiation. A powder of the sample was placed on a glass slide for the analysis. UV-Visible Absorbance spectra were measured by using a Perkin Elmer lambda 35 scanning spectrometer with the sample in a 2 mm cells. Photoluminescence (PL) spectra were recorded with excitation laser centred at 402 nm (Nichia-NLVH 3000E). The light is then dispersed by a monochromator PI Acton SpectraPro 2500i. The detection is done 90 by CDD camera (Spec-10:100 BR/LN). Acquisition is performed by Winspec32 software. For absolute determinations of quantum yield (QY), an integrating sphere (Labsphere) was used. QY measurements were performed in air-saturated solution at room temperature. For the calculation, standard procedure was performed using the procedure described in the literature. 3 The luminescence parts of the curves were fitted with a GaussAmp function on Origin software before the calculation of the integrated emission. S4

5 2. Analysis of InP QDs 1 4 Figure S1. (a) TEM image, (b) X-ray diffractogram, (c) UV-Vis spectrum of InP QDs 1. The inset of panel (a) shows the size distribution of the QDs (2.0 ± 0.3 nm) Figure S2. (a) TEM image, (b) X-ray diffractogram, (c) UV-Vis spectrum of InP QDs 2. The inset of panel (a) shows the size distribution of the QDs (4.1 ± 0.4 nm) Figure S3. (a) TEM image, (b) X-ray diffractogram, (c) UV-Vis spectrum of InP QDs 3. The inset of panel (a) shows the size distribution of the QDs (4.5 ± 0.4 nm) S5

6 Figure S4. (a) TEM image, (b) X-ray diffractogram, (c) UV-Vis spectrum of InP QDs 4. The inset of panel (a) shows the size distribution of the QDs (4.3 ± 0.4 nm) S6

7 3. Solid State NMR analysis of InP QDs 1 4 Figure S5. (a) 31 P Hahn-echo MAS NMR spectrum of InP QDs 1 (spinning speed 16 khz), (b) 31 P CP MAS NMR spectrum of InP QDs 1 (spinning speed 18 khz) Figure S6. 1 H MAS NMR of InP QDs 1 (spinning rate 16 khz). : grease S7

8 1 H- 13 C CP-MAS C MAS (ppm) C Chemical Shift (ppm) Figure S7. Comparison between 1 H- 13 C CP-MAS and 13 C MAS NMR spectra of InP QDs 1. (spinning rate 16 khz). : grease Figure S8. (a) 31 P Hahn-echo MAS NMR spectrum of InP QDs 2 (spinning speed 16 khz), (b) 31 P CP MAS NMR spectrum of InP QDs 2 (spinning speed 18 khz) S8

9 1 H- 13 C CP-MAS * * 13 C MAS (ppm) 120 * C Chemical Shift (ppm) Figure S9. Comparison between 1 H- 13 C CP-MAS and 13 C DP MAS NMR spectra of InP QDs 2. (spinning rate 16 khz). (*: residual mesitylene, : grease) Figure S10. (a) 31 P Hahn-echo MAS NMR spectrum of InP QDs 3 (spinning speed 16 khz), (b) 31 P CP MAS NMR spectrum of InP QDs 3 (spinning speed 18 khz) S9

10 Figure S11. 1 H MAS NMR of InP QDs 3 (spinning rate 16 khz) 1 H- 13 C CP-MAS C MAS (ppm) C Chemical Shift (ppm) Figure S12. Comparison between 1 H- 13 C CP-MAS and 13 C MAS NMR spectra of InP QDs 3 (spinning rate 16 khz) S10

11 P Chemical Shift (ppm) Figure S P Hahn-echo MAS NMR spectrum of InP QDs 4 (spinning speed 16 khz) 1 H- 13 C CP-MAS C MAS * * (ppm) C Chemical Shift (ppm) Figure S14. Comparison between 1 H- 13 C CP-MAS and 13 C MAS NMR spectra of InP QDs 4 (spinning rate 16 khz). *: mesitylene S11

12 Figure S15. (a) Experimental (blue) and simulated (red) 2 H- 1 H CP-MAS spectrum of InP QDs 4 (spinning rate 8 khz). The simulated spectrum was slightly shifted to facilitate comparison. (b, c, d) simulated spectra of the signal at 9.0, 3.05 and 2.15 ppm (khz) Figure S16. 2 H solid-echo MAS NMR spectrum of a PA/HDA solution in mesitylene after heating at 230 C for 21h under D 2 at 1.8 bar (spinning rate 16 khz) S12

13 4. TEM Images of Growing Experiments Figure S17. TEM images of growth experiments performed with InP QDs 3 after a) 1st addition (4.5 ± 0.4 nm), b) 2nd addition (5.2 ± 0.6 nm), c) 3rd addition (5.3 ± 0.6 nm), d) 4rd addition (5.4 ± 0.5 nm), e) 5th addition (5.4 ± 0.6 nm), f) 6th addition (6.2 ± 0.6 nm), and g) 7th addition (6.7 ± 0.6 nm) Figure S18. TEM images of growth experiments performed with InP QDs 2 after a) 1st addition (3.9 ± 0.3 nm), b) 2nd addition (4.0 ± 0.5 nm), c) 3rd addition (4.2 ± 0.4 nm), and d) 4rd addition (4.4 ± 0.4 nm) S13

14 5. Analysis of QDs 5 6 InP = Ligands 2-3 OLA 1) Zn(stearate) 2 (5 eq), 190 C, 0.5 h 2) TOP-S (5 eq), C, 1.5 h 3) Zn(stearate) 2 (3.5 eq), 230 C, 0.5 h 4) TOP-S (3.5 eq), 260 C, 0.5 h 5) Zn(stearate) 2 (1.7 eq), 260 C, 0.5 h InP InP/ZnS OLA = 5-6 Scheme S1. Synthesis of InP/ZnS QDs 5 6. TOP: Trioctylphosphine, OLA: Oleylamine Figure S19: TEM image of InP@ZnS QDs 5. The size distribution of the QDs is 4.5 ± 0.5 nm. Figure S20: UV-Vis (black), and PL (red) spectra of InP@ZnS QDs 5. S14

15 Figure S21: TEM image of QDs 6. The size distribution of the QDs is 5.2 ± 0.6 nm. Figure S22: UV-Vis (black), and PL (red) spectra of QDs 6. S15

16 5. References (1) M. D. Tessier, D. Dupont, K. D. Nolf, J. D. Roo, Z. Hens, Chem. Matter. 2015, 27, (2) D. Massiot, F. Fayon, M. Capron, I. King, S. Le Calve, B. Alonso, J. O. Durand, B. Bujoli, Z. Gan, G. Hoatson, Magn. Reson. Chem. 2002, 40, (3) C. Würth, M. Grabolle, J. Pauli, M. Spieles, U. Resch-Genger, Nat. Protoc. 2013, 8, S16