Structure Transition And Helical Self-Assembly In The Collapse Process Of Carbon Nanorings

Helical self-assembly nanostructure, due to its ideal geometric arrangement, adaptive and unique nanoscale properties, has gained ever-increasing interest on both theoretical researches and potential application Studying of new helical self-assembly nanostructure will push the development of novel nanodevices forward. Carbon nanoring (CNR) with a large diameter tend to be thermodynamic unstable and collapse to ribbon shape, making its spiral arrangement possible. Until now, studies concerning spiral growth of carbon nanoring have not been performed. A detailed and convincing simulation of carbon nanoring becomes valuable to understand growth theory and potential application of helical nanostructure.In this work, systematic molecular dynamics (MD) simulations are performed to disclose the serf-assembling behavior of CNR and structure transition mechanism, and finally explain the thermodynamic condition and driving force in the self-scrolling process. The main results are shown as follows.(1) Molecular dynamics (MD) simulations are carried out to model the interaction between CNR and single wall carbon nanotube (SWCNT). Results show that, CNR positioned in one open end of SWCNT can be captured by the hollow interior of SWCNT, and finally helically insert into SWCNT to form a DNA-like double-helix. Moreover, directed by Van der Waals interaction, CNR can spontaneously collapse to a linked double graphitic nanoribbon and helically wrap around the tube. The result of size effect on the self-assembling system has demonstrated that, for a CNR with certain length, the diameter of SWCNT must exceed one threshold to guarantee the successful helical insertion of CNR Two CNRs can also be encapsulated in the interior of SWCNT to form a perfect helix. The dangling σ-orbitals on the CNR atoms can be utilized to deliver substances, biological molecules, and genes to the confined SWCNT.(2) We exp lore the interaction between CNR and A1Nanowire (NW). A1NW can guide and activate the CNR to collapse and helically scroll, finally forming a size-controllable concentric cable-like structure. The cross section of Al NWs has a negligible effect on the helical configuration, whereas the size (diameter and length) of CNRs should meet some requirements to guarantee the helix-forming process. Compared to the final scroll and stacking structure, the helical nanostructure of hydrogen-terminated CNR is energetically more stable.(3) We further study the structure transition process of CNR and Ni NW self-assembly process. As a result of the combined action of van der Waals interaction and offset face-to-face π-π stacking interaction, CNR can spontaneously collapse and wrap around Ni NW forming a double-deck helix. Therefore, It is a general phenomenon that CNR can self-scroll around the metallic NW to form double-deck helix.An exhaustive investigation has been performed to demonstrate the interaction between CNR and SWCNT/NW, which will probably provide theoretical support to the design of novel helical structure and potential application of the composite CNR/NW core/shell structure.