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

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.


The conformational phase diagram λ vs ζ.The co-existence lines are the set of critical points (λ, ζ) at which a new phase arises. The solid lines are the theoretically predicted critical curves. The gray, red and blue colors correspond to twist-helix, helix-scroll and scroll-fold transitions, respectively. The dotted blue line is prediction for the helix-scroll transition with a larger value of the interaction area fraction, α = 2.
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f3: The conformational phase diagram λ vs ζ.The co-existence lines are the set of critical points (λ, ζ) at which a new phase arises. The solid lines are the theoretically predicted critical curves. The gray, red and blue colors correspond to twist-helix, helix-scroll and scroll-fold transitions, respectively. The dotted blue line is prediction for the helix-scroll transition with a larger value of the interaction area fraction, α = 2.

Mentions: We develop a more complete understanding of the stable phases by performing simulations with varying Lk and ribbon aspect ratios w/L (Methods). The results are shown in Fig. 3 as a conformational phase diagram, λ vs. ζ = 2πLk/L, the link density. Representative conformations are shown alongside. The initial twist is more stable at larger ζ due to the increasing pre-stretch, but in all cases small end displacements near λ ≈ 1 result in a spontaneous transition to a helix. The scrolled phase dominates for smaller values of λ, as expected. Close to the scroll-fold transition curve (ζ ≈ 0.25 at small λ), we see co-existing scrolls and multilayered folds; an example conformation is shown alongside. High values of ζ do not lead to any new phases. The response is a bit different as the larger ribbon width and pre-stretch leads to scroll formation before the ribbon relaxes out the intrinsic twist and the ribbon is stretched. The localized instability is a tightly wound helix that resembles an axially slit nanotube; an example is shown in Supplementary Figure 1.


Shaping van der Waals nanoribbons via torsional constraints: Scrolls, folds and supercoils
The conformational phase diagram λ vs ζ.The co-existence lines are the set of critical points (λ, ζ) at which a new phase arises. The solid lines are the theoretically predicted critical curves. The gray, red and blue colors correspond to twist-helix, helix-scroll and scroll-fold transitions, respectively. The dotted blue line is prediction for the helix-scroll transition with a larger value of the interaction area fraction, α = 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: The conformational phase diagram λ vs ζ.The co-existence lines are the set of critical points (λ, ζ) at which a new phase arises. The solid lines are the theoretically predicted critical curves. The gray, red and blue colors correspond to twist-helix, helix-scroll and scroll-fold transitions, respectively. The dotted blue line is prediction for the helix-scroll transition with a larger value of the interaction area fraction, α = 2.
Mentions: We develop a more complete understanding of the stable phases by performing simulations with varying Lk and ribbon aspect ratios w/L (Methods). The results are shown in Fig. 3 as a conformational phase diagram, λ vs. ζ = 2πLk/L, the link density. Representative conformations are shown alongside. The initial twist is more stable at larger ζ due to the increasing pre-stretch, but in all cases small end displacements near λ ≈ 1 result in a spontaneous transition to a helix. The scrolled phase dominates for smaller values of λ, as expected. Close to the scroll-fold transition curve (ζ ≈ 0.25 at small λ), we see co-existing scrolls and multilayered folds; an example conformation is shown alongside. High values of ζ do not lead to any new phases. The response is a bit different as the larger ribbon width and pre-stretch leads to scroll formation before the ribbon relaxes out the intrinsic twist and the ribbon is stretched. The localized instability is a tightly wound helix that resembles an axially slit nanotube; an example is shown in Supplementary Figure 1.

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.