SUPPORTING INFORMATION

Transcription

1 SUPPORTING INFORMATION Shape Control of Colloidal Cu 2-x S Polyhedral Nanocrystals by Tuning the Nucleation Rates Ward van der Stam, Sabine Gradmann, Thomas Altantzis, Xiaoxing Ke, Marc Baldus, Sara Bals and Celso de Mello Donega* Condensed Matter and Interfaces, Debye Institute for Nanomaterials Science, Utrecht University, P.O. Box 80000, 3508 TA Utrecht, The Netherlands NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Department of Chemistry, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium Corresponding Author: *c.demello-donega@uu.nl S1

2 Figure S1. (a,d,g,j) 1D Powder Electron Diffraction (PED) patterns of four Cu 2-x S nanocrystal samples. 1D PED patterns were obtained by radially integrating 2D Electron Diffraction patterns displayed in (b,e,h,k). In the case of excess Cu compared to Sn, polyhedral Cu 2-x S NCs with the lowchalcocite crystal structure are formed. An increase of the Sn concentration results in Cu 2-x S nanoplatelets with the djurleite crystal structure. The 2D ED patterns were acquired on areas containing a large number of nanocrystals (c,f,i,l), in order to get statistically valid 1D PED patterns. Colors denote the TEM, 2D ED and 1D PED of the same samples (cyan; thin nanoplatelets, blue; thick nanoplatelets, red; bipyramids, green; bifrustums). Figure S2. (a) X-ray Diffractograms of high aspect ratio Cu 2-x S nanoplatelets (red line) and hexagonal Cu 2-x S bipyramids (blue line). (b) Calculated XRD patterns for djurleite and low-chalcocite. Red bars in both panels denote the XRD pattern for the djurleite crystal structure, while the blue bars denote the XRD pattern for low-chalcocite crystal structure. The patterns are very similar, but the djurleite peak at around 46 is shifted toward smaller angles in low-chalcocite. The bipyramid NCs closely match the chalcocite phase, while the nanoplatelets match the djurleite phase. S2

3 Figure S3. HRTEM image (left) and corresponding FFT pattern (right) of a single hexagonal bipyramid Cu 2-x S NC, viewed along the [010] direction, revealing the characteristic diffraction spots of the monoclinic low-chalcocite crystal structure. Figure S4. Transmission Electron Microscopy images of Cu 2-x S NCs synthesized after (a) the addition of halides in the form of CuBr and (b) after the addition of Sn(OAc) 4. Concentrations of Cu:halide and Cu:Sn are the same as in the synthesis protocol for hexagonal Cu 2-x S bipyramids, i.e. Cu:halide 1:2 in (a) and Cu:Sn 2:1 in (b). Scale bars correspond to 100 nm. S3

4 Figure S5. (a) High-Angle Annular Dark Field Scanning Transmission Electron Microscopy image of hexagonal bipyramid Cu 2-x S NCs. (b) Energy-Dispersive X-ray spectroscopy (EDS) chemical mapping of the NCs shown in (a). Sn is present at low concentrations (2-3%) and is not homogeneously distributed, but is concentrated on nanocrystals that appear larger and morphologically distinct from the majority of the ensemble. S4

5 Figure S6. (a) Dark-field STEM image of high aspect ratio Cu 2-x S hexagonal nanoplatelets. The yellow rectangle indicates the region on which elemental mapping was performed (displayed in b). (b) Energy-Dispersive X-ray spectroscopy (EDS) elemental maps of the Cu 2-x S nanoplatelets shown in panel (a). (c) Dark-field STEM image of a stack of high aspect ratio Cu 2-x S hexagonal nanoplatelets. The long white arrow indicates the direction of an EDS linescan across the stack, which is shown in panel (d). The short white arrows in panel c correspond to the black arrows in panel d. These measurements indicate that Sn is not concentrated in any particular facet. The Sn-rich spot in panel (b) is probably due to residual SnBr x complexes that were not removed by the washing procedure used to purify the NCs, since it does not contain significant amounts of Cu and S. S5

6 Figure S7. Solid-state and solution 119 Sn NMR spectra of polyhedral Cu 2-x S nanocrystals and pre-nucleation reaction products. (a) Solid-state 119 Sn NMR spectrum of high aspect ratio Cu 2-x S nanoplatelets (black line) and solution 119 Sn NMR spectra (blue, CuCl and SnBr 4 mixed in the same concentration and ratio used to synthesize the nanoplatelets, and red, SnBr 4 only). (b) Solid-state 119 Sn NMR spectrum of low aspect ratio Cu 2-x S nanoplatelets (black line) and solution 119 Sn NMR spectra (blue, CuCl and SnBr 4 mixed in the same concentration and ratio used to synthesize the nanoplatelets, and red, SnBr 4 only). (c) Solid-state 119 Sn NMR spectra of Cu 2-x S hexagonal bipyramids without MAS (red line) and with 5 khz MAS (blue line), and solution 119 Sn NMR spectrum (black line, SnBr 4 only). The insets denote the nanocrystal morphology and the Cu:Sn ratio in the reaction mixture. Figure S8. 1 H-NMR spectra of three solution based samples, where all combinations of metal salts were mixed in a DDT/OLAM mixture, just below the nucleation temperature (~180 C), to make sure + all precursors can form without nucleation of Cu 2-x S NCs. The peak at 5 ppm stems from R-NH 3 compounds formed after deprotonation of thiol molecules by amines. The broad peak at 2 ppm is characteristic for alkyl chains. A peak at 7.8 ppm is observed, corresponding to a proton in close proximity to a Sn-atom. S6

7 Figure S9. Solid-state 1 H-NMR spectra of Cu 2-x S bipyramids and Cu 2-x S nanoplatelets. No evidence for surface bound amines is found, which would give rise to a broad signal at 5.5 ppm. Instead, sharp signals are observed, which indicate mostly unbound organic molecules. Reference 1 H-NMR spectra of dodecanethiol and oleylamine are added for clarity. S7