Research ArticleCHEMICAL PHYSICS

Direct quantitative measurement of the C═O⋅⋅⋅H–C bond by atomic force microscopy

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Science Advances  12 May 2017:
Vol. 3, no. 5, e1603258
DOI: 10.1126/sciadv.1603258
  • Fig. 1 Chemical structures.

    (A) TNP (29, 30) and (B) TFAP. The top panel shows the top (side) view, and the bottom panel shows the side (top) view for the upright (side-lying) configuration.

  • Fig. 2 Experimental observations of TNP and TFAP on Ag(111).

    (A to F) Series of STM topographies (A, C, and E) of TNP deposited on the Ag(111) surface with increasing coverage and corresponding AFM images (B, D, and F). As the coverage of TNP increases, the ratio of the upright (red arrows) and side-lying (yellow arrow) TNP becomes larger. (G) STM topography of upright TFAP and (H) corresponding AFM image. Measurement parameters: For STM observations, tunneling current I = 1.0 pA and bias voltage V = −300 mV (A), I = 0.8 pA and V = −200 mV (C), I = 0.8 pA and V = −200 mV (E), and I = 0.8 pA and V = 500 mV (G); for AFM observations, oscillation amplitude A = 60 pm and V = 0 mV (B, D, F, and H).

  • Fig. 3 Quantitative measurements of the C–O⋅⋅⋅H–C bond.

    (A) Schematic drawing of the hydrogen bonding measurement on TFAP with a CO-functionalized tip. Right shows the AFM image. Scale bar, 300 pm. (B) Two-dimensional frequency shift map. (C) Calculated force and (D) potentials. Inset shows the same area with a wider contrast. The z origin was set at the position of the hydrogen atom. Measurement parameters: A = 60 pm and V = 0 mV.

  • Fig. 4 Simulated results on the TFAP molecule.

    (A) Calculated total energy plot as a function of tip position over the molecule. The molecular structure in the bottom panel is at the height included in the simulation setup, such that the energies plotted along the x axis are at 150 pm from the hydrogen atoms. (B) Zoomed-in image of the area shown by a dashed green line in (A), where the green star shows the lowest energy position used in the other three images. (C) Snapshot of the system configuration. (D) Calculated charge density at a contour of 0.05 eV·Å−1. (E) Differential charge density at contours of −0.05 (red) and 0.05 eV·Å−1 (blue).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/5/e1603258/DC1

    fig. S1. STM topography of standing TNP molecules.

    fig. S2. Electrostatic potential surface maps.

    fig. S3. Force spectroscopy of TNP.

    fig. S4. AFM images of TNP.

    fig. S5. AFM images of TFAP.

    fig. S6. Detailed explanation of force spectroscopy.

    fig. S7. Simulated AFM images of TNP and TFAP.

    fig. S8. Simulated AFM images of upright TFAP.

    fig. S9. Simulated AFM images of side-lying TNP.

    fig. S10. Atomistic snapshots of the tip-surface system.

    fig. S11. Simulated results on the upright TNP molecule.

    References (46, 47)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. STM topography of standing TNP molecules.
    • fig. S2. Electrostatic potential surface maps.
    • fig. S3. Force spectroscopy of TNP.
    • fig. S4. AFM images of TNP.
    • fig. S5. AFM images of TFAP.
    • fig. S6. Detailed explanation of force spectroscopy.
    • fig. S7. Simulated AFM images of TNP and TFAP.
    • fig. S8. Simulated AFM images of upright TFAP.
    • fig. S9. Simulated AFM images of side-lying TNP.
    • fig. S10. Atomistic snapshots of the tip-surface system.
    • fig. S11. Simulated results on the upright TNP molecule.
    • References (46, 47)

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