The Role of Acid in Modulating Precursor Conversion in InP-QD Synthesis

Transcription

1 Supporting Information to Accompany: The Role of Acid in Modulating Precursor Conversion in InP-QD Synthesis Dylan C. Gary and Brandi M. Cossairt* Contents: Additional experimental details, selected 1 H NMR spectra for starting materials (Figures S1, S2), UV-Vis time aliquots for InP growth using P(SiMe 3 ) 3 and HP(SiMe 3 ) 2 (Figures S3, S4), 31 P{ 1 H} spectra of P(SiMe 3 ) 3 + acid control experiments (Figure S5), 31 P{ 1 H} spectra of P(SiMe 3 ) 3 + octylammonium myristate control experiments (Figure S6), 31 P{ 1 H} NMR spectra of early time aliquots from selected InP syntheses (Figure S7), FWHM comparison for tetrabutylammonium myristate versus myristic acid (Figure S8), TEM analysis of particles grown with P(SiMe 3 ) 3 and HP(SiMe 3 ) 2 (Figure S9), and complete mechanistic picture for acid-catalyzed speciation pathway (Figure S10). Additional Experimental Details Procedures for in situ Aliquoting for 31 P { 1 H} NMR: Room Temperature Control: An indium myristate solution with excess myristic acid was prepared from indium acetate (0.117 grams mmoles) and myristic acid (0.331 grams 1.45 mmoles) in 1-octadecene. This solution was placed under a flow of nitrogen, and allowed to come to room temperature. A syringe of P(SiMe 3 ) 3 (58 µl, 0.20 mmol) in 1-octadecene was prepared in a nitrogen filled glovebox and sealed by inserting the needle of the syringe into a 14/20 Suba seal septum. An NMR tube was sealed with a septum and the seal was secured with electrical tape in the glovebox. The syringe and the NMR tube were removed from the glovebox. A 1 ml glass syringe was outfitted with a 19G needle and inserted into the indium myristate solution. The P(SiMe 3 ) 3 solution was injected into the indium myristate solution, and approximately 0.4 ml of the reaction solution was immediately drawn into the glass syringe and injected into the NMR tube for analysis. Competitive Phosphine Control Experiment: An indium myristate solution was prepared from indium acetate (0.117 g, 0.40 mmoles) and myristic acid (0.27 g, 1.2 mmol) in 1- octadecene. A 0.10 mmol solution of HP(SiMe 3 ) 2 in 2.5 g of 1-octadecene was prepared in the same manner as previously employed above. A syringe with 290 µl of P(SiMe 3 ) 3 in 2.5 g of 1-octadecene was prepared along with two NMR tubes sealed with septa and wrapped with electrical tape in manner previously employed above. Approximately ten hours after injecting the sparged methanol into the Schlenk flask, the syringe of P(SiMe 3 ) 3 and the sealed NMR tubes were removed from the glovebox. The P(SiMe 3 ) 3 solution was injected into the HP(SiMe 3 ) 2 solution with vigorous stirring, and 0.4 ml of the resulting solution was drawn and injected into one of the sealed NMR tubes to confirm approximately equal proportions of both targeted phosphines. A dry ice/acetone bath was prepared in a wide mouth dewer flask. The NMR tube was removed from the glovebox and suspended in the dry ice/acetone bath. The indium myristate solution was then heated to 316 o C. The temperature controller was then set to keep a temperature of 285 o C. The syringe and the NMR tube were removed from the glovebox. A 1 ml glass syringe was outfitted with a 19G needle and inserted into the indium myristate solution. The temperature controller was set to keep a temperature of 285 o C. The P(SiMe 3 ) 3 solution was injected into the indium myristate solution just as the solution fell to the temperature reading of 315 o C and approximately 0.4 ml of the reaction solution was immediately drawn into the glass syringe and injected into the NMR tube for analysis. Procedure for Gaussian Fitting: Gaussian curves were fit to the UV-Vis data in Excel using the equation:

2 f(x,σ)= B + Aexp(-1*(x 0 -x 2 )/(2σ 2 )) Where B is equal to the energy of absorbance at 1.55 ev (assumed to have no contribution from the nanoparticles), A is equal to the absorbance of the lowest energy electronic transition, 2σ is the full width at half max of the distribution, and x 0 is the energy of the lowest energy electronic transition. The quality of each fit for each distribution was judged on the criteria that: 1. The absorbance at 1.55 ev be set as the baseline of the distribution (B= absorbance at 1.55 ev) 2. The difference between the distribution and the real data be minimal from the point of inflection of the UV-Vis data and the peak of the distribution. 3. The amplitude of the distribution be as close to the absorbance at the least energetic energy transition as possible without sacrificing too much in criteria 2.

3 1 H NMR Spectra of [NBu 4 ][O 2 C(CH 2 ) 12 CH 3 ] and [H 3 N(CH 2 ) 7 CH 3 ][O 2 C(CH 2 ) 12 CH 3 ] Figure S1. 1 H NMR spectrum of [NBu 4 ][O 2 C(CH 2 ) 12 CH 3 ] in C 6 D 6. Figure S2. 1 H NMR spectrum of [NBu 4 ][O 2 C(CH 2 ) 12 CH 3 ] in C 6 D 6.

4 UV-Vis Spectra of Timed Aliquots from InP Reaction Mixtures Figure S3. UV-Vis spectra of timed aliquots from reaction with P(SiMe 3 ) 3 : 0.40 mmol In(O 2 CCH 3 ) 3, 1.45 mmol myristic acid, 0.20 mmol P(SiMe 3 ) 3, 315 C inject, 285 C grow. Figure S4. UV-Vis spectra of timed aliquots from reaction with HP(SiMe 3 ) 2 : 0.40 mmol In(O 2 CCH 3 ) 3, 1.20 mmol myristic acid, 0.20 mmol P(SiMe 3 ) 3, 315 C inject, 285 C grow.

5 Protonolysis of P(SiMe 3 ) 3 with Various Acids Confirmed by 31 P{ 1 H} NMR Spectroscopy Figure S5. 1 H NMR spectra of reactions resulting from addition of CH 3 OH (top), HCl (middle), and HO 2 C(CH 2 ) 12 CH 3 (bottom) to P(SiMe 3 ) 3 in C 6 D 6. Spectra were allowed to proceed to completion, requiring approximately 10 hours for CH 3 OH, and only 10 minutes for the stronger acids.

6 31 P{ 1 H} NMR Controls for Protonolysis by Myristic Acid vs. Octylammonium Myristate Figure S6. 1 H NMR spectra of reactions resulting from addition of [H 3 N(CH 2 ) 7 CH 3 ][O 2 C(CH 2 ) 12 CH 3 ] (top) and HO 2 C(CH 2 ) 12 CH 3 (bottom) to P(SiMe 3 ) 3 in C 6 D 6. Spectra were obtained approximately 10 minutes after mixing at room temperature and showed no further changes with time.

7 31 P{ 1 H} NMR of InP Reaction Aliquots Taken Within Ten Seconds of Injection of P(TMS) 3 Solution Figure S7. 31 P{ 1 H} NMR spectra of InP reaction mixture aliquots obtained immediately (within 10 s) after injection of P(SiMe 3 ) 3 at 315 C (top) and 20 C (bottom).

8 Data Analysis for InP Syntheses Using Tetrabutylammonium Myristate at 315 C Injection Temperature Figure S8. Transmission Electron Microscopy Images of Nanoparticles Prepared with HP(SiMe3)2 and P(SiMe3)3 With Ideal Concentrations of Myristic Acid Figure S9. InP QDs synthesized with P(SiMe3)3 InP QDs synthesized with HP(SiMe3)2

9 Figure S10. General acid-catalyzed mechanistic scheme including all protonolysis pathways. Note: R = (CH 2 ) 12 CH 3 ; n = 1-3.