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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.


(top) Schematic of a suspended supercoiled nanoribbon subject to a torsional constraint.The relative rotation between the two ends sets the degree of supercoiling Lk. (bottom) The strategy used to explore the bent and twisted conformations for z < L. Magnified view of the ribbon (boxed) illustrating the ribbon and tangent vectors,  and  respectively, associated with the material frame used to describe the ribbon conformation.
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f1: (top) Schematic of a suspended supercoiled nanoribbon subject to a torsional constraint.The relative rotation between the two ends sets the degree of supercoiling Lk. (bottom) The strategy used to explore the bent and twisted conformations for z < L. Magnified view of the ribbon (boxed) illustrating the ribbon and tangent vectors, and respectively, associated with the material frame used to describe the ribbon conformation.

Mentions: In this article, we present a facile route to engineering topologically distinct soft conformations of nanoscale ribbons. Figure 1 depicts the scenario schematically; a finite-length nanoribbon of width w is torsionally constrained by rotating one end relative to the other and clamping the two ends. The end conditions take the form of a fixed degree of supercoiling Lk and controlled end displacement λ = z/L. The choice is motivated by the fact that, unlike the end couple (moment M and tension T), the rigid loading variables λ and Lk are more accessible and can be easily manipulated15. For a ribbon so constrained, the partitioning of the initial twist (the Twist, Tw) into energetically favorable bent shapes (the Writhe, Wr) follows from the well-known Călugăreanu-White-Fuller theorem161718, Lk = Tw + Wr. The geometric partitioning is amplified by the vanishingly small thickness of the nanoribbon that favors bends and twists relative to in-plane deformations, and forms the basis for the paradigm that we employ to shape these nanoribbons. The approach is bioinspired in that it is also exploited to control the properties of natural filaments such as supercoiled DNA, α-helices, elastomers, and textile fibers and their yarns192021222324, yet little is known about analogous conformations in these van der Waals (vdW) nanoribbons.


Shaping van der Waals nanoribbons via torsional constraints: Scrolls, folds and supercoils
(top) Schematic of a suspended supercoiled nanoribbon subject to a torsional constraint.The relative rotation between the two ends sets the degree of supercoiling Lk. (bottom) The strategy used to explore the bent and twisted conformations for z < L. Magnified view of the ribbon (boxed) illustrating the ribbon and tangent vectors,  and  respectively, associated with the material frame used to describe the ribbon conformation.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: (top) Schematic of a suspended supercoiled nanoribbon subject to a torsional constraint.The relative rotation between the two ends sets the degree of supercoiling Lk. (bottom) The strategy used to explore the bent and twisted conformations for z < L. Magnified view of the ribbon (boxed) illustrating the ribbon and tangent vectors, and respectively, associated with the material frame used to describe the ribbon conformation.
Mentions: In this article, we present a facile route to engineering topologically distinct soft conformations of nanoscale ribbons. Figure 1 depicts the scenario schematically; a finite-length nanoribbon of width w is torsionally constrained by rotating one end relative to the other and clamping the two ends. The end conditions take the form of a fixed degree of supercoiling Lk and controlled end displacement λ = z/L. The choice is motivated by the fact that, unlike the end couple (moment M and tension T), the rigid loading variables λ and Lk are more accessible and can be easily manipulated15. For a ribbon so constrained, the partitioning of the initial twist (the Twist, Tw) into energetically favorable bent shapes (the Writhe, Wr) follows from the well-known Călugăreanu-White-Fuller theorem161718, Lk = Tw + Wr. The geometric partitioning is amplified by the vanishingly small thickness of the nanoribbon that favors bends and twists relative to in-plane deformations, and forms the basis for the paradigm that we employ to shape these nanoribbons. The approach is bioinspired in that it is also exploited to control the properties of natural filaments such as supercoiled DNA, α-helices, elastomers, and textile fibers and their yarns192021222324, yet little is known about analogous conformations in these van der Waals (vdW) nanoribbons.

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.