Research ArticleMATERIALS SCIENCE

Confirmation of a de novo structure prediction for an atomically precise monolayer-coated silver nanoparticle

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Science Advances  25 Nov 2016:
Vol. 2, no. 11, e1601609
DOI: 10.1126/sciadv.1601609
  • Fig. 1 X-ray–determined structure and comparisons with the theoretical de novo prediction.

    (A) X-ray–determined structure for (TOA)3AuAg16(TBBT)12 optimized through first-principles relaxation, viewed down a threefold axis. The AuAg12 icosahedral core [with the central gold atom (purple) surrounded by 12 silver atoms (red)] is capped by four tetrahedrally located silver atoms (green), each bonded to three sulfur atoms (yellow) forming quasi-planar Ag(TBBT)3 mounts. The carbon atoms of the 12 TBBT ligands are represented by gray spheres, with the light gray spheres corresponding to hydrogen atoms. The TOA+ counterions were faded for clarity, and the octyl carbon chains and the hydrogen atoms are represented by light pink and light gray spheres, respectively; the nitrogens of four trapped nitrobenzene molecules are shown as small light blue spheres. (B to G) In the comparisons between predicted and measured structures, the TOA+ cations are omitted. (B and C) The predicted and x-ray–determined structures of the AuAg12 icosahedral core (B) and the four outer Ag atoms [green spheres in (C)] coincide. Below, the predicted structure is shown on the left, and the measured one is shown on the right. (D and E) The structures with the sulfur atoms (yellow) and the quasi-planar mounts. Each S atom is shown as bonded to the nearest carbon atom (dark and light blue spheres) of the thiol ligand (TBBT), with the S–C bond direction predicted by first-principles simulations of the structure (D), as well as the x-ray–determined one (E). In (D), the S–C bonds are all oriented in a clockwise sense, and in (E), they are oriented in a clockwise sense for one of the mounts (see white arrow) and in an anticlockwise sense for the other three mounts (light blue); see also insets. (F) View showing paired ligands on neighboring mounts; in (G), partial bundle ordering is found. Three pair-bundled TBBT ligands (in red, pink, and green), a single triple-bundled one (in blue), and three unpaired ligands (in gray) are identified (see further details in Fig. 4 and the Supplementary Materials).

  • Fig. 2 Electronic and optical properties.

    (A) Angular momentum–projected DOS (PDOS) calculated for the DFT-relaxed (TOA)3AuAg16(TBBT)12 + 4NC2H3 structure; color code shown on the right, and Fermi energy EF = 0.0 eV. The inset gives a focused view on the interval (−2.3 eV < EEF < −0.9eV). The calculated PDOS was broadened by a Gaussian function with σ = 0.03 eV. (B) Representative wavefunction portraits, superimposed on the atomic structure of the cluster and corresponding to the indicated energies (blue and purple signify different wavefunction signs). The nodal structures of the delocalized orbitals exhibit 1S, 1P, and 1D superatom states. The d(Au) portrait shows a d-wavefunction on the central Au atom, and the d(Ag) one is a typical atomic d-wavefunction of the Ag atoms. (C) Plotted measured (green line) and TDDFT-calculated (red line) optical absorption spectra versus wavelength and energy (inset). The calculated spectrum was broadened (0.02 eV−1) by a Lorentzian function, and the abscissa was scaled by 1.095 to simulate a solvachromic shift.

  • Fig. 3 Silver mount motifs.

    (A) Silver thiolate polymer, from which each mount is derived; (B) AgS3 monomer; (C) Ag2S5 dimer; and (D) Ag3S6 trimer mount. For (B) to (D), top and side views are shown, whereas for (A), only the former is displayed.

  • Fig. 4 Ligand (TBBT) bundling.

    (A and B) Views along the threefold axis from the front (A) and back (B) of the nanocluster, showing the L3 (trimer) bundle (dark blue), the three L2 (dimer) bundles (in pink, green, and red), and the unbundled three ligands (gray/white spheres). (C) A view showing the T-like orientation of the two phenyl rings in each of the L2 dimers. Also shown in light blue are the three trapped acetonitrile solvent molecules. The silver atoms are depicted as gray spheres, the central Au atom is shown in orange, and the S atoms are colored yellow. For further details, see the Supplementary Materials (particularly fig. S2, where the definitions and values of geometrical parameters describing the T-like dimers and cyclic trimers can be found).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/11/e1601609/DC1

    fig. S1. Optical micrograph of a typical orange colored orthorhombic crystal of (TOA)3AuAg16(TBBT)12.

    fig. S2. Definitions of distances and angles used in analyzing the bundling geometries (Fig. 4).

    Detailed interpretation of the TDDFT optical absorption (Fig. 2C)

    Comparison of x-ray–determined and theoretically optimized structures

    Bader charge distribution

    Analysis of the superatom peaks in the PDOS (Fig. 2A)

    Analysis of ligand bundling

    Single-crystal x-ray diffraction and analysis

    Structural analysis of (TOA)3AuAg16(TBBT)12

    table S1. Contributions of different angular momentum components (s, p, d,…) to the superatom peaks in the calculated PDOS (Fig. 2A).

    table S2. Geometrical parameters describing the cyclic trimer formed by the L3 bundled ligands (upper part of table) and the T-like L2 ligand dimers (lower part of table).

    table S3. Sample and crystal data for (TOA)3AuAg16(TBBT)12.

    table S4. Data collection and structure refinement for (TOA)3AuAg16(TBBT)12.

    table S5. Atomic coordinates and equivalent isotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.

    table S6. Bond lengths (Å) for (TOA)3AuAg16(TBBT)12.

    table S7. Bond angles (°) for (TOA)3AuAg16(TBBT)12.

    table S8. Anisotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.

    table S9. Hydrogen atomic coordinates and isotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Optical micrograph of a typical orange colored orthorhombic crystal of (TOA)3AuAg16(TBBT)12.
    • fig. S2. Definitions of distances and angles used in analyzing the bundling geometries (Fig. 4).
    • Detailed interpretation of the TDDFT optical absorption (Fig. 2C)
    • Comparison of x-ray–determined and theoretically optimized structures
    • Bader charge distribution
    • Analysis of the superatom peaks in the PDOS (Fig. 2A)
    • Analysis of ligand bundling
    • Single-crystal x-ray diffraction and analysis
    • Structural analysis of the (TOA)3AuAg16(TBBT)12
    • table S1. Contributions of different angular momentum components (s, p, d,…) to the superatom peaks in the calculated PDOS (Fig. 2A).
    • table S2. Geometrical parameters describing the cyclic trimer formed by the L3 bundled ligands (upper part of table) and the T-like L2 ligand dimers (lower part of table).
    • table S3. Sample and crystal data for(TOA)3AuAg16(TBBT)12.
    • table S4. Data collection and structure refinement for (TOA)3AuAg16(TBBT)12.
    • table S5. Atomic coordinates and equivalent isotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.
    • table S6. Bond lengths (Å) for (TOA)3AuAg16(TBBT)12.
    • table S7. Bond angles (°) for (TOA)3AuAg16(TBBT)12.
    • table S8. Anisotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.
    • table S9. Hydrogen atomic coordinates and isotropic atomic displacement parameters (Å2) for (TOA)3AuAg16(TBBT)12.

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