Research ArticlePHYSICS

Dipole-like electrostatic asymmetry of gold nanorods

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Science Advances  09 Feb 2018:
Vol. 4, no. 2, e1700682
DOI: 10.1126/sciadv.1700682
  • Fig. 1 Schematic description of possible electrostatic potential in AuNRs.

    (A) Typical morphology and surface facets of AuNR grown with CTAB surfactant. The top view shows possible complexity of facets composing ends of AuNR. The colored areas present possible variation of {111} facet area. (B) Expected electrostatic potential at outer surface of CTAB with equal (case 1) and unequal (case 2) capping for two ends.

  • Fig. 2 Electrostatic properties of individual AuNRs.

    Phase map (A and C) and profiles (B and D) along the longitudinal axis of the AuNRs supported by silicon grids with (A and B) and without (C and D) CTAB coating. Blue and red curves are extracted from their phase shift maps by EH and HAADF images, respectively. (E) Capacitance gradient (dC/dZ) image and (F) line profiles of individual (dashed) particles and average curve (solid, black) along long axis, obtained by Kelvin probe microscopy. a.u., atomic unit.

  • Fig. 3 Noncentrosymmetric distribution of CTAB on AuNR.

    (A, D, and E) STEM-HAADF and (B, F, and G) SEM images for a same gold NR. (D to G) Atomic resolution images of the side (D and F) and end (E and G) sections of the AuNR. (C) Carbon element map and (H) carbon profile along the white arrow obtained by EF-TEM.

  • Fig. 4 Computational analysis of electrostatic properties for AuNRs.

    (A) Surface charge density of the CTAB layer. (B and D) Electric potential on the surface of gold and CTAB layer, respectively. (C) Electric potential line plot in the CTAB layer and cross-sectional view of electric potential of CTAB-AuNR. (E) Surface charge density on surface of gold. (F) Voltage (orange) and phase shift (violet) slope of AuNRs with various aspect ratios obtained by computation and experimental EH data, respectively. Both values are linearly fitted as dashed lines with R2 value of 0.999 (orange) and 0.971 (violet).

  • Fig. 5 Asymmetrical optical properties of AuNRs.

    (A and B) Comparison of simultaneously obtained SHG and FL images of AuNRs. Max intensity projection of same z stacks of SHG (A) and FL (B) with same gray scale. The scale bars represent 1 μm. (C) Histogram of relative intensity of SHG compared to FL from 119 of individual AuNRs. Note that blue-colored bar represents the AuNRs having zero intensity. (D) NPL from AuNRs embedded in PSS (black, decoupled; red, coupled) and PVA (blue) matrix.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/2/e1700682/DC1

    Supplementary Materials

    Supplementary Methods

    Supplementary Discussion

    fig. S1. Computations of plasmon modes of silver nanowire (NW) with and without a neighbor particle.

    fig. S2. HAADF images of AuNRs and analysis of capacitance gradient (dC/dz) profiles obtained by Kelvin probe microscopy.

    fig. S3. Ligand exchange of CTAB on AuNRs with PSS and PVA.

    fig. S4. e-beam ablation for selective removal of CTAB on single AuNRs and their plasmon mapping.

    fig. S5. Intensity of individual AuNRs in SHG- and FL-mode imaging.

    fig. S6. LBL-assembled AuNR/PSS films.

    fig. S7. Computation of plasmon modes of AuNRs with and without centrosymmetrical gold core geometry.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials
    • Supplementary Methods
    • Supplementary Discussion
    • fig. S1. Computations of plasmon modes of silver nanowire (NW) with and without a neighbor particle.
    • fig. S2. HAADF images of AuNRs and analysis of capacitance gradient (dC/dz) profiles obtained by Kelvin probe microscopy.
    • fig. S3. Ligand exchange of CTAB on AuNRs with PSS and PVA.
    • fig. S4. e-beam ablation for selective removal of CTAB on single AuNRs and their plasmon mapping.
    • fig. S5. Intensity of individual AuNRs in SHG- and FL-mode imaging.
    • fig. S6. LBL-assembled AuNR/PSS films.
    • fig. S7. Computation of plasmon modes of AuNRs with and without centrosymmetrical gold core geometry.

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