Defining Rules for the Shape Evolution of Gold Nanoparticles

Transcription

1 Supporting Information for Defining Rules for the Shape Evolution of Gold Nanoparticles Mark R. Langille, Michelle L. Personick, Jian Zhang, Chad A. Mirkin* Department of Chemistry and International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois Experiment Standard Conditions Variations Reducing Agent Halides in the Absence of Silver Silver Trace Halides in the Presence of Silver High Concentrations of Halides in the Presence of Silver Overgrowth of Concave Cubes in CTA-Br 10.0 ml 10 mm CTA-Br μl10 mm AuCl μl large seeds 10.0 ml 50 mm CTA-Cl 500 μl large seeds 10.0 ml 100 mm CTA-Cl μl 1M HCl 0.1 μl small seeds 10.0 ml 40 mm CTA-Cl 0.6 ml 1M NaCl μl 1M HCl 0.1 μl small seeds 10.0 ml 100 mm CTA-Cl or Br μl 1M HCl μl 10 mm AgNO μl small seeds μl 10 mm AuCl μl 10 mm AgNO μl 100 mm AA concave cubes seeds Chart S1. Summary of Reaction Conditions. 0.05, 0.20, or 1.0 ml 100 mm AA Bromide: 0.0, or 50.0 μl 1M NaBr Iodide: 0.0,10.0, or 75.0 μl 10 mm NaI 10.0, 40.0, or μl 10 mm AgNO 3 Bromide: 10.0 μl 10 mm AgNO 3 with 0.0, 10.0, 20.0, or 50.0 μl 10 mm NaBr 40.0 μl 10 mm AgNO 3 with 0.0, or 40.0 μl 10 mm NaBr Iodide: 10.0 μl 10 mm AgNO 3 with 0.0, 1.0, 5.0, or 10.0 μl 0.1 mm NaI Seemain text 10.0 ml 100 mm or 20 mm CTA-Br S1

2 Ag : Au Counts (a.u.) Ag : Au Figure S1. SEM image of {111}-faceted octahedra produced by slightly lowering the concentration of ascorbic acid in the growth solution to 0.5 mm. This shows that cubes and octahedra are very close in surface energy to one another. Scale bar: 200 nm. B) Ag 3500 A) Au 3d 3/2 3d 5/ Au Ag C C) Concentration Binding Energy of Bromide (ev) (μm) Au 4f 7/2 4f 5/ Binding Energy (ev) Concentration Binding Energy of Bromide (ev) ( μm) Figure S2. (A) Representative XPS survey scan and high resolution XPS spectra of (B) Ag 3d and (C) Au 4f peaks used in determining surface silver/gold ratios for nanoparticles formed under various reaction conditions. S2

3 Figure S3. XPS data showing the silver coverage on the particles formed with various concentrations of sodium bromide in the growth solution, compared to the published experimental silver coverage in the absence of bromide (black squares). 10 μm silver nitrate (red triangles) with 0.0 μm, 10 μm, 20 μm, 50 μm sodium bromide, and 40 μm silver nitrate (blue circles) with 0 μm, 40 μm sodium bromide. Figure S4. SEM images of reaction products from growth solutions containing 40 mm CTA-Cl, 40 μm silver nitrate and (A) 0.0 μm and (B) 40 μm sodium bromide. Scale bars: 200 nm. In the S3

4 absence of bromide, {310}-faceted truncated ditetragonal prisms are formed and with 40 μm bromide, {720}-faceted concave cubes are produced. (C) XPS data showing the silver/gold ratio for particles generated with different concentrations of bromide in the growth solution, showing that as the bromide concentration is increased, the amount of silver on the particles surface also increases. Figure S5. SEM images of reaction products from growth solutions containing 40 mm CTA-Cl, 10 μm silver nitrate and (A) 0.00 μm (B) 0.01 μm (C) 0.05 μm and (D) 0.10 μm sodium iodide. Scale bars: 200 nm. In the absence of iodide, a mixture of {110}-faceted bipyramids and {110}- faceted rhombic dodecahedra are produced. With increasing iodide, the size and yield of the bipyramids decrease while the size and yield of the rhombic dodecahedra increase. At 0.10 μm iodide, {310}-faceted truncated ditetragonal prisms are generated. (E) XPS data showing the silver/gold ratio for particles generated with different concentrations of iodide in the growth solution, showing that as the iodide concentration is increased, the amount of silver on the particles surface also increases. (F) ICP-AES kinetics data of the reactions containing 0.00 μm (black squares), 0.05 μm (red triangles), and 0.10 μm (blue cicles) of sodium iodide. Final gold concentrations are higher with increasing iodide because the destabilization of the Ag UPD layer by iodide allows more gold to be reduced onto the particle surface before the reaction comes to completion. S4

5 Figure S6. SEM images of tetrahexahedra produced using growth solutions containing 100 mm CTA-Br and (A) 40 μm silver nitrate and (B) 100 μm silver nitrate. Scale bars: 200 nm. Figure S7. Schematic of reaction products from solutions containing 100 μm silver nitrate in solutions of (A) 100 mm CTA-Cl, (B) 100 mm CTA-Cl and 100 mm sodium bromide, (C) 100 mm CTA-Br, and (D) 100 mm CTA-Br and 100 mm sodium chloride. Scale bars: 200 nm. At 100 μm silver nitrate, all of the reactions which contain bromide produce tetrahexahedra (B-D) and concave cubes are only produced in the absence of bromide (A). This demonstrates that the effects of bromide dominate over chloride. S5

6 Figure S8. SEM images of particles produced in reaction solutions containing 10 μm silver nitrate and (A) 100 mm CTA-Br and (B) 25 mm CTA-Br. Scale bars: 200 nm. With low silver and high CTA-Br, growth is uncontrolled, resulting in stellated particles (A). When the CTA-Br concentration is decreased, more silver is able to deposit on to the particle surface, enabling the stabilization of tetrahexahedra (B). Figure S9. SEM images of particles produced in reactions containing 500 μm silver and concave cube seeds in (A) 100 mm CTA-Br and (B) 20 mm CTA-Br. Scale bars: 200 nm. At high concentrations of CTA-Br, bromide inhibits silver deposition and overgrown concave cubes are formed (A), while at 20 mm CTA-Br, silver is able to stabilize {111}-facets, leading to the formation of octahedra (B). S6

7 Figure S10. SEM image of particles formed in growth solutions containing 10 μm silver, 100 mm CTA-Cl and 10 μm sodium iodide. Scale bar: 200 nm. The presence of iodide leads to poorly controlled growth and particles with extremely stellated features. Figure S11. TEM images of concave cubes at early stages of growth. (A) 8 minutes, (B) 14 minutes, (C) 20 minutes, and (D) 26 minutes. Scale bars: 50 nm. Even at the beginning of their growth, the particles already possess a concave cubic shape. S7