Research ArticleNANOSTRUCTURES

Ligand-induced twisting of nanoplatelets and their self-assembly into chiral ribbons

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Science Advances  13 Sep 2017:
Vol. 3, no. 9, e1701483
DOI: 10.1126/sciadv.1701483
  • Fig. 1 NPL TEM characterization and drying assembly scheme.

    TEM (A and B) and STEM (C) images of the CdSe NPLs in their native form after synthesis and purification. They are 1.5 nm thick, 7 nm wide, and 22 nm long [inset of (A)]. (D) Scheme of the evaporation protocol used to obtain twisted ribbons.

  • Fig. 2 Structural analysis of the twisted ribbons.

    (A to D) TEM images of twisted ribbons of various lengths at different magnifications. (E and F) HAADF-STEM images of twisted ribbons. The twist of the individual NPLs is small. (G) SAXS pattern of a dispersion of twisted ribbons. The two scattering peaks, at 1.0075 and 2.0141 nm−1, respectively, are the first and second orders of diffraction from the NPL stacking and give the stacking period d = 5.84 nm. From this period, we deduce that there are around 70 NPLs within one pitch and that the mean rotation angle between two adjacent NPL is 5°. (H) Scheme of the twisted ribbon formation mechanism. Initially, flat NPLs are dispersed in solution. A first addition of OA followed by drying induces the formation of straight ribbons, which twist upon further addition of OA and drying. (I) 3D model from the tomographic reconstruction of a twisted ribbon.

  • Fig. 3 Twisting of individual NPLs.

    (A to C) Electron microscopy of NPLs dispersed in solution upon increasing concentration of OA. In the absence of added OA (A), the NPLs are flat; the proportion of twisted NPL increases with the amount of added OA (B and C). (D to F) HAADF-STEM images of twisted NPLs. (G) Statistics of twisted and flat platelets counted on the TEM grid as a function of the quantity of OA added. (H) Scheme of the initially flat NPL twisting under the effect of the addition of OA.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/9/e1701483/DC1

    fig. S1. TEM images at different steps of the twisted threads formation.

    fig. S2. SAXS patterns at different steps of the twisted threads formation.

    fig. S3. Fourier transform IR (FTIR) spectra of NPL dispersions at different steps of the twisted thread formation.

    fig. S4. Electron tomography of individually twisted NPLs.

    fig. S5. High-resolution HAADF-STEM images of twisted NPLs.

    fig. S6. Crystallographic structure of CdSe NPLs.

    fig. S7. FTIR spectra of NPL dispersions in solution with varying amounts of OA without drying (that is, without assembly into threads).

    table S1. Position of the vibration bands for the symmetric and antisymmetric stretching bands corresponding to the spectra of fig. S3.

    table S2. Position of the vibration bands for the symmetric and antisymmetric stretching bands corresponding to the spectra of fig. S7.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. TEM images at different steps of the twisted threads formation.
    • fig. S2. SAXS patterns at different steps of the twisted threads formation.
    • fig. S3. Fourier transform IR (FTIR) spectra of NPL dispersions at different steps of the twisted thread formation.
    • fig. S4. Electron tomography of individually twisted NPLs.
    • fig. S5. High-resolution HAADF-STEM images of twisted NPLs.
    • fig. S6. Crystallographic structure of CdSe NPLs.
    • fig. S7. FTIR spectra of NPL dispersions in solution with varying amounts of OA without drying (that is, without assembly into threads).
    • table S1. Position of the vibration bands for the symmetric and antisymmetric stretching bands corresponding to the spectra of fig. S3.
    • table S2. Position of the vibration bands for the symmetric and antisymmetric stretching bands corresponding to the spectra of fig. S7.

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