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Shaping van der Waals nanoribbons via torsional constraints: Scrolls, folds and supercoils

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ABSTRACT

Interplay between structure and function in atomically thin crystalline nanoribbons is sensitive to their conformations yet the ability to prescribe them is a formidable challenge. Here, we report a novel paradigm for controlled nucleation and growth of scrolled and folded shapes in finite-length nanoribbons. All-atom computations on graphene nanoribbons (GNRs) and experiments on macroscale magnetic thin films reveal that decreasing the end distance of torsionally constrained ribbons below their contour length leads to formation of these shapes. The energy partitioning between twisted and bent shapes is modified in favor of these densely packed soft conformations due to the non-local van der Waals interactions in these 2D crystals; they subvert the formation of supercoils that are seen in their natural counterparts such as DNA and filamentous proteins. The conformational phase diagram is in excellent agreement with theoretical predictions. The facile route can be readily extended for tailoring the soft conformations of crystalline nanoscale ribbons, and more general self-interacting filaments.

No MeSH data available.


(a–b) Atomic configurations of a GNR (a) with and (b) without long range vdW interactions. In both cases, the ribbon is subject to an end displacement of λ = 0.65 (arrows). (c–d) Results of a macroscale experiments on (c) double-sided magnetic tape, and (d) simple elastic tape. The aspect ratio and the degree of supercoiling of the tapes are chosen to be the same as that of the GNRs, i.e. w/L ≈ 0.01 and Lk = 7.5.
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f4: (a–b) Atomic configurations of a GNR (a) with and (b) without long range vdW interactions. In both cases, the ribbon is subject to an end displacement of λ = 0.65 (arrows). (c–d) Results of a macroscale experiments on (c) double-sided magnetic tape, and (d) simple elastic tape. The aspect ratio and the degree of supercoiling of the tapes are chosen to be the same as that of the GNRs, i.e. w/L ≈ 0.01 and Lk = 7.5.

Mentions: The dense scrolls and folds that we observe are rarely observed in soft ribbon-like assemblies due to the inherent self-avoidance in these solvated polymeric systems. There are exceptions, such as the formation of hairpin loops in folded β-sheet domains in proteins and in DNA/RNA which are stabilized by long-range interactions such as hydrogen bonding and specific base-pair interactions29. Clearly, the long-range vdW interactions have a decisive effect on the nature of the writhed conformations as they are comparable to the elastic energies associated with conformations i.e. bending and twist. As validation, we have repeated the computations by turning off the long-range vdW interactions. The direct comparison is shown in Figs. 4a and 4b for a GNR of length L = 110 nm and width w = 2 nm, subject to supercoiling Lk = 7.5 and an end displacement λ = 0.65. The scroll formation is suppressed (Fig. 4a) and it now forms a classical plectoneme phase that grows with decreasing λ (Fig. 4b, Supplementary Video 5).


Shaping van der Waals nanoribbons via torsional constraints: Scrolls, folds and supercoils
(a–b) Atomic configurations of a GNR (a) with and (b) without long range vdW interactions. In both cases, the ribbon is subject to an end displacement of λ = 0.65 (arrows). (c–d) Results of a macroscale experiments on (c) double-sided magnetic tape, and (d) simple elastic tape. The aspect ratio and the degree of supercoiling of the tapes are chosen to be the same as that of the GNRs, i.e. w/L ≈ 0.01 and Lk = 7.5.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5384089&req=5

f4: (a–b) Atomic configurations of a GNR (a) with and (b) without long range vdW interactions. In both cases, the ribbon is subject to an end displacement of λ = 0.65 (arrows). (c–d) Results of a macroscale experiments on (c) double-sided magnetic tape, and (d) simple elastic tape. The aspect ratio and the degree of supercoiling of the tapes are chosen to be the same as that of the GNRs, i.e. w/L ≈ 0.01 and Lk = 7.5.
Mentions: The dense scrolls and folds that we observe are rarely observed in soft ribbon-like assemblies due to the inherent self-avoidance in these solvated polymeric systems. There are exceptions, such as the formation of hairpin loops in folded β-sheet domains in proteins and in DNA/RNA which are stabilized by long-range interactions such as hydrogen bonding and specific base-pair interactions29. Clearly, the long-range vdW interactions have a decisive effect on the nature of the writhed conformations as they are comparable to the elastic energies associated with conformations i.e. bending and twist. As validation, we have repeated the computations by turning off the long-range vdW interactions. The direct comparison is shown in Figs. 4a and 4b for a GNR of length L = 110 nm and width w = 2 nm, subject to supercoiling Lk = 7.5 and an end displacement λ = 0.65. The scroll formation is suppressed (Fig. 4a) and it now forms a classical plectoneme phase that grows with decreasing λ (Fig. 4b, Supplementary Video 5).

View Article: PubMed Central - PubMed

ABSTRACT

Interplay between structure and function in atomically thin crystalline nanoribbons is sensitive to their conformations yet the ability to prescribe them is a formidable challenge. Here, we report a novel paradigm for controlled nucleation and growth of scrolled and folded shapes in finite-length nanoribbons. All-atom computations on graphene nanoribbons (GNRs) and experiments on macroscale magnetic thin films reveal that decreasing the end distance of torsionally constrained ribbons below their contour length leads to formation of these shapes. The energy partitioning between twisted and bent shapes is modified in favor of these densely packed soft conformations due to the non-local van der Waals interactions in these 2D crystals; they subvert the formation of supercoils that are seen in their natural counterparts such as DNA and filamentous proteins. The conformational phase diagram is in excellent agreement with theoretical predictions. The facile route can be readily extended for tailoring the soft conformations of crystalline nanoscale ribbons, and more general self-interacting filaments.

No MeSH data available.