Research ArticlePHYSICAL SCIENCES

Molecular “surgery” on a 23-gold-atom nanoparticle

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Science Advances  19 May 2017:
Vol. 3, no. 5, e1603193
DOI: 10.1126/sciadv.1603193
  • Fig. 1 Molecular surgery on the atomically precise 23-gold-atom nanocluster by a two-step metal-exchange method: peeling off two parts of the cluster wrapper and closing the gaps with two P–C–P plasters.

    (A) Schematic of the molecular surgery on [Au23(SR)16]; all carbon tails are omitted for clarity. (B) Site-specific surface motif tailoring with a two-step metal-exchange method. The transformation from [Au23(SR)16] through [Au23−xAgx(SR)16] (x ~ 1) to [Au21(SR)12(P–C–P)2]+ is revealed by single-crystal x-ray analysis. Magenta and blue, Au; gray, Ag; yellow, S; orange, P; green, C; light green, Cl. Other C and all H atoms are omitted for clarity.

  • Fig. 2 Comparison of the [Au23(SR)16], [Au23−xAgx(SR)16], and [Au21(SR)12(P–C–P)2]+ structures.

    (A) Crystal structure of [Au23(SR)16]. Left: 15-atom Au bipyramidal core. Right: Au23S16 framework. (B) Crystal structure of [Au23−xAgx(SR)16]. Left: 15-atom Au–Ag bipyramidal core. Right: Au23−xAgxS16 framework. (C) Crystal structure of [Au21(SR)12(P–C–P)2]+. Left: 15-atom bipyramidal core. Right: Au21S12(P–C–P)2 framework. Magenta and blue, Au; gray, Ag; yellow, S; orange, P; green, C. Other C and all H atoms are omitted for clarity. The counterions TOA+ and AgCl2 are also omitted.

  • Fig. 3 Single-crystal structure and optical properties of [Au21(SR)12(P–C–P)2]+[AgCl2].

    (A) The counteranion [AgCl2] and coordination of PPh2CH2PPh2 motifs. Other carbon tails and all H atoms are removed for clarity. (B) Total structure and arrangement of [Au21(SR)12(P–C–P)2]+[AgCl2] in a single-crystal unit cell. Magenta, Au; gray, Ag; yellow, S; orange, P; green, C; light green, Cl; white, H. (C) UV-Vis absorption spectrum of [Au21(SR)12(P–C–P)2]+. (D) PL spectrum of the Au21 (solid line); the PL efficiency is enhanced ~10 times compared to Au23 (dashed line). Inset shows a photograph of the Au21 sample under 365-nm UV light.

  • Fig. 4 Metal-exchange transformation from [Au23(SR)16] to [Au21(SR)12(P–C–P)2]+ and [Au25−xAgx(SR)18].
  • Fig. 5 DFT-calculated free energies (ΔGrxn) of elementary reaction steps of the experimentally synthesized pure and Ag-doped Au nanoclusters.

    Detailed reaction network energetics analysis can be found in table S4. Inset shows the different (thermodynamically stable) doping positions of Ag in the Au15 core of the [Au23−xAgx(SR)16] clusters. The different energy levels of the [Au23−xAgx(SR)16] clusters represent the lowest-energy isomers (based on doping positions of the inset), which are also analyzed in fig. S8.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/5/e1603193/DC1

    X-ray Experimentals

    fig. S1. UV-Vis absorption spectra of [Au23(SR)16] and [Au23−xAgx(SR)16].

    fig. S2. MALDI mass spectra of [Au23(SR)16] (black), [Au23−xAgx(SR)16] (green), and [Au21(SR)12(P–C–P)2]+ (gray) sample.

    fig. S3. ESI mass spectrum of [Au21(SR)12(P–C–P)2]+.

    fig. S4. 31P-NMR spectrum of [Au21(SR)12(P–C–P)2]+.

    fig. S5. UV-Vis absorption spectra of samples with increasing mass ratio of AgI(SR) that reacted with [Au23(SR)16].

    fig. S6. X-ray crystal structure of [Au25−xAgx(SR)18] (x ~ 4).

    fig. S7. AgI(SR) complex–induced transformation from [Au23(SR)16] to heavily Ag-doped [Au25−xAgx(SR)18].

    fig. S8. DFT-relaxed [Au23−xAgx(SR)18] (x = 1 to 3) and [Au25−yAgy(SR)18] (y = 2, 3) nanoclusters and associated relative electronic energies.

    table S1. Atomic percentages of Au and Ag in the [Au21(SR)12(P–C–P)2]+[AgCl2] obtained by EDS-SEM.

    table S2. DFT free energies of reactions of intermediates and possible reaction pathways.

    table S3. Crystal data and structure refinement for Au22.13Ag0.87(SR)16 TOA+.

    table S4. Crystal data and structure refinement for Au20.51Ag4.49(SR)18 TOA+.

    table S5. Crystal data and structure refinement for [Au21(SR)12(P–C–P)2]+[AgCl2].

  • Supplementary Materials

    This PDF file includes:

    • X-ray Experimentals
    • fig. S1. UV-Vis absorption spectra of Au23(SR)16 and Au23−xAgx(SR)16.
    • fig. S2. MALDI mass spectra of Au23(SR)16 (black), Au23−xAgx(SR)16 (green), and Au21(SR)12(P–C–P)2+ (gray) sample.
    • fig. S3. ESI mass spectrum of Au21(SR)12(P–C–P)2+.
    • fig. S4. 31P-NMR spectrum of Au21(SR)12(P–C–P)2+.
    • fig. S5. UV-Vis absorption spectra of samples with increasing mass ratio of AgI(SR) that reacted with Au23(SR)16.
    • fig. S6. X-ray crystal structure of Au25−xAgx(SR)18 (x ~ 4).
    • fig. S7. AgI(SR) complex–induced transformation from Au23(SR)16 to heavily Ag-doped Au25−xAgx(SR)18.
    • fig. S8. DFT-relaxed Au23−xAgx(SR)18 (x = 1 to 3) and Au25−yAgy(SR)18 (y = 2, 3) nanoclusters and associated relative electronic energies.
    • table S1. Atomic percentages of Au and Ag in the Au21(SR)12(P–C–P)2+AgCl2 obtained by EDS-SEM.
    • table S2. DFT free energies of reactions of intermediates and possible reaction pathways.
    • table S3. Crystal data and structure refinement for Au22.13Ag0.87(SR)16 TOA+.
    • table S4. Crystal data and structure refinement for Au20.51Ag4.49(SR)18 TOA+.
    • table S5. Crystal data and structure refinement for Au21(SR)12(P–C–P)2+AgCl2.

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