MD Simulations Of Self-scroll Properties Of Functionalized Graphene Sheets

Graphene,a single layer of sp²-bonded carbon atoms arranged in a honeycomb lattice,continues to attract enormous interest due to its intriguing electronic properties,excellent mechanical,magnetic and optical properties,which endow graphene with wide potential applications in sensors,photonics and electronic devices.It’s very difficult to characterize their properties because of the nanosize of graphene,while molecular dynamaic（MD）simulation method provides a new way to investigate these nano materials.Based on the MD simulations,the main purpose of this article is to study the self-scroll properties of functionalized graphene membranes,including C₄H-type hydrogenated graphene and C₄H/C₄F-type graphene superlattice.The self-scroll mechanism and process of functionalized graphene are clearly elucidated as well as other influencing factors such as size effect,proportions,directions of hydrogenation and fluorination,and geometry of graphene.Firstly,it’s demonstrated by MD simulations that C₄H-type hydrogenated graphene can self-scroll at room temperature.The main driving force of the self-scroll of C₄ H is due to the one-sided distribution of hydrogen and the corresponding asymmetric orientation of sp3 bonding,and there exist strongly electrostatic repulsion between the relatively close H atoms.It is also found that vdW force plays an important role in the formation and stability of CNS.The simulations show that C₄ H can self-scroll into various carbon nanoscroll（CNS）structures,which is mainly controlled by its geometry（size and aspect ratio）.And carbon nanotube（CNT）is a good candidate to activate and guide C₄ H to form CNS,whose core size can be controlled.Meanwhile,a novel CNT/C₄ H core/shell composite nanostructure is also formed.The theoretical results shed important light on a feasible approach to fabricate high-quality CNS and other novel nanostructures including core/shell structures,which hold great potential applications in optics,optoelectronics devices,hydrogen storage,sensors,and energy storage in supercapacitors or batteries.Then,morphology manipulation opens up a new avenue for controlling and tailoring functional properties of graphene,enabling the exploration of graphene based nanomaterials.Through single-sided hydrogenation graphene（C₄H）mixed with fluorination graphene（C₄F）on one single sheet,the C₄H/C₄F-type graphene superlattices can self-scroll into a variety of well-defined CNS structures at room temperature.We demonstrate by using MD simulations that different proportions,sizes,directions of hydrogenation and fluorination,and geometry of graphene have a great influence on the self-scroll of superlattices into a variety of well-defined CNS,thus providing a controllable approach to tune its structures.Based on molecular mechanics（MM）simulations,the CNS bears more than eight times radial pressure than that of multiwalled carbon nanotube（MWNT）counterparts and it also shows an excellent radial elasticity of CNS,indicating that it can be used as ideal fillers in nanocomposites for high load mechanical support.Compared with conventional CNS,the novel CNS is endowed with more ample and flexible heterogeneous structures due to on-demand hydrogenation and fluorination.Our simulation results will be of great importance in the fabrication of novel carbon nanoscrolls,which could significantly reduce the research period and the cost.Besides,it can also reduce the workload,effectively provide some theoretical guidance for the experimental direction,and verify the accuracy and the precision of the experimental results.It is expected that our work can stimulate the further research of properties and applications of C₄X-type structures and its composites,and lead to further development of a broad new class of heterogeneous materials with enhanced properties,and even facilitate the research of other core/shell structures.