Self-assembly Configuration Evolution And Extended Functional Structure Design Of Graphene

In recent years,the graphene with high-quality and large area has received widespread attention in the field of nanoscience due to its excellent mechanical,electrical,and optical properties.It is promising to be used in the fields of composites,nanodevices,biomedicine,and energy storage materials,which causing graphene application shifts from the laboratory to practical industry.These developments fundamentally benefit from the perfect two-dimensional nanostructures of graphene,while self-assembly is one of the common preparation methods closely related to the nanostructure evolution of the material.The self-assembly of graphene opens the self-assembly door for 2D atomic crystal materials and makes people aware of the importance of 2D self-assembly.How to use the self-assembly character of graphene to produce nano-industrial devices with specific structures and functions has become an interesting research topic.The related researches not only provide new ideas for the application of simple graphene,but also lay the foundation for the development of nano or macro graphene composite.At present,there have been some achievements of graphene self-assembly,but most of them is limited to the preparation method and parameter.The detailed microstructure,properties,and evolution mechanism of self-assembly have not received enough attention,and there is still much room for the functional application based on this self-assembly behavior.This dissertation combines molecular dynamics as well as first principles calculation and focuses on the dynamics details of graphene's self-assembly.It is dedicated to the comprehensive research on the self-assembly spiraling,uncoiling,and functional application,which is aimed to construct a computational simulation research from mechanism finding,behavior controlling to further model design of graphene self-assembly,and look forward to their application prospects The primary coverage and results of the dissertation are as follows(1)This dissertation studies the self-assembled spiral and configuration evolution of multiple graphene nanoribbons in nanotubes,and clarifies the mechanism role of van der Waals force in the evolution of its self-assembly.The results show that several graphene nanoribbons can self-assemble into carbon nanotubes simultaneously due to van der Waals force,and then tangle together to form a perfect spiral structure to maximize the ?-? stacking area.The spiral self-assembly may be accompanied by spontaneous configuration changes,and their final helical configuration of graphene is influenced by the combined effect of structure stability,initial arrangement,and tube space.In this study,we also propose two equations that can be used to predict the self-assembled results and verify their accuracy.(2)In further behavior controlling research,we reveal that doping partial boron nitride fragments into graphene nanoribbons can help the helical nanoribbons spontaneously uncoil and causes the system to show a harmonic "spiral-stretch" oscillation.The self-assembled harmonic change is caused by the competition between the induction of graphene and the resistance of boron nitride,and accompanied by a system energy exchange between non-bonding energy and elastic potential energy,suggesting the electrical signal change in the oscillation process because the electronic transmission capacity of the nanoribbon changes with helical angle.The size and composition of the nanoribbons will affect the results of the spiral oscillation.(3)Based on the self-assembly mechanism and combined the self-assembly with biomimicry,an octopus-shaped graphene nanogripper model is functionally designed in this dissertation.The nanogripper can self-assembled capture many common metal particles over a wide temperature range and then confine them in the graphene cage for transportation.The van der Waals force in the system drives the self-assembly,and the grasping strength of nanogripper is influenced by the element type of targets,causing a specific grasping priority for gripper in multi-element system.Through adding a circular graphene substrate and an appropriately high temperature for recovery,the graphene nanogripper can achieve its own recyclable.In summary,this dissertation explores the self-assembly details and mechanism of graphene at the atomic level,which is of great significance for the functional design and application of graphene self-assembly.We hope the results can provide theoretical guidance for improvement and optimization of existing graphene nanodevices in the future,and further promote the actual application of graphene self-assembly,especially in the low-cost preparation of graphene-related nanocomposites,nanomaterial(such as drug and gene)transfer,testing and screening.