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Chiromagnetic nanoparticles and gels

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Science  19 Jan 2018:
Vol. 359, Issue 6373, pp. 309-314
DOI: 10.1126/science.aao7172
  • Fig. 1 Synthesized chiral Co3O4 NPs.

    (A) Circular dichroism (CD), (B) g-factor, defined as the ratio between the molar circular dichroism Δε and the molar extinction coefficient ε(g = Δε/ε), and (C) UV-visible absorption spectra of Co3O4 NPs stabilized by d-Cys, l-Cys, and dl-Cys. (D) Photographs of light transmitting through the NPs, with the rotation of the linear analyzer counterclockwise (–10°), and clockwise (+10°). (E) TEM image of l-Cys–capped Co3O4 NPs. mdeg, millidegrees; a.u., arbitrary units.

  • Fig. 2 Rotations of crystalline structures.

    (A and B) d-Cys (A) and l-Cys (B) Co3O4 NPs. Sulfur atoms are the larger red spheres forming one corner of the tetrahedra, and the remaining atoms depicted in red are C–C–C–O from the Cys ligands. (C and D) Raman (C) and Raman optical activity (ROA) (D) backscattering spectra with 532-nm excitation of d-Cys and l-Cys Co3O4 NPs in scattered circular polarization ROA mode. These spectra are courtesy of BioTools. (E) Hausdorff chirality measure (HCM) for the NP cores. (F) Dihedral angles between atoms 18, 7, 9, and 22 [O–Co(III)–Co(III)–O] of l-Cys and d-Cys Co3O4 NPs.

  • Fig. 3 Computed atomic geometry of chiral nanoparticles.

    (A to C) Graphical representation of the dihedral angles formed by four atoms: ϕ35-12-11-22 (red), ϕ35-17-8-18 (blue), and ϕ35-13-14-27 (green). A detailed description of the atomic types and numbering of each dihedral angle may be found in fig. S21. (A) NP with ideal crystallographic structure. (B) NP with M-d-Cys after 2000 fs of MD simulation. (C) NP with P-l-Cys after 2000 fs of MD simulation. The direction from the S atom to the carbonyl atom in the Cys molecules is taken as the basis for the geometry classification according to the Cahn-Ingold-Prelog rules. Ligands have been omitted for clarity. (D to I) Ramachadran plots for chiral NPs: two-dimensional probability maps for the relative orientation of adjoining octahedra pairs sharing the O atom number 35. Average probabilities were computed along the 2000-fs MD simulation for the NP functionalized with either M-d-Cys (left) or P-l-Cys (right). The isovalues depicted in the plots are probabilities of 0.0002 (blue), 0.0003 (green), 0.0004 (yellow), 0.0005 (orange), and 0.001 (red).

  • Fig. 4 Optical modulation.

    (A and B) CD and MCD (A) and corresponding absorbance spectra (B) of l-Cys and d-Cys Co3O4 NPs. (C) Photograph of the optically transparent gel made from l-Cys Co3O4 NPs. (D) Emission intensities of fluorescent paper plus the NP gel in front, with a magnetic field applied to the NP gel (red and blue) and without a magnetic field (green) (excitation, 280 nm). (E) Cycling performance of the NP gel’s absorbance at 280 nm with and without magnetic fields. (F) Cycling profile of emission intensity at 415 nm with and without magnetic fields and corresponding photographs of blue-emitting light from the fluorescent paper.

Supplementary Materials

  • Chiromagnetic nanoparticles and gels

    Jihyeon Yeom, Uallisson S. Santos, Mahshid Chekini, Minjeong Cha, André F. de Moura, Nicholas A. Kotov

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S33
    • Tables S1 to S15
    • Schemes S1 to S3
    • Captions for Movies S1 to S5
    • References

    Images, Video, and Other Media

    Movie S1
    Animation for the Co3O4 model NP normal mode at 201 cm-1.
    Movie S2
    Animation for the Co3O4 model NP normal mode at 301 cm-1.
    Movie S3
    Animation for theCo3O4 model NP normal mode at 400 cm-1.
    Movie S4
    Animation for the Co3O4 model NP normal mode at 500 cm-1.
    Movie S5
    Animation for the AIMD simulation of the Co3O4 model NP capped with Lcysteine (upper panel) or D-cysteine (lower panel).
    Correction (29 January 2018): reference (71) was added to clarify that the sTD-DFT with improved CD spectra followed the method outlined in that paper.
    The original version is accessible here.

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