边缘变形石墨烯片的自折叠与自卷曲机制：一项分子动力学研究
Self-Folding and Self-Scrolling Mechanisms of Edge-Deformed Graphene Sheets: A Molecular Dynamics Study
AI总结：
本研究通过ReaxFF分子动力学模拟，探究边缘扭转的扶手椅边缘卷曲石墨烯的自变形行为，揭示扭转角、温度对其形成纳米折叠或纳米卷的调控规律，发现了温度无关的折叠-卷曲双态结构。
摘要：
石墨烯基纳米折叠（GNFs）是由单层石墨烯衍生而来的边缘连接的二维堆叠单层结构。石墨烯基纳米卷（GNSs）是几何形态类似石墨烯层卷成螺旋（纸莎草纸状）的纳米材料。GNS和GNF结构都会使单层石墨烯的力学与光电性质发生显著变化，为碳基应用聚集了新的功能。本文开展了全原子反应性（ReaxFF）分子动力学模拟，研究边缘变形石墨烯片的自折叠与自卷曲行为。我们采用了初始扶手椅边缘卷曲石墨烯（AESG($ϕ$,$θ$)）结构，其两个边缘具有相似（或不同）的扭转角（$ϕ$,$θ$），模拟了实验中用于形成双卷片的初始构型。结果表明，AESG(0,$2π$)和AESG($2π$,$2π$)分别演变为单折叠和双折叠的完全堆叠形貌。总体趋势为，当扭转角大于$2π$时，AESG形貌的自变形过程会生成GNSs。小于$π$的边缘扭转角不足以触发自变形过程。在AESG(0,$3π$)和AESG($3π$,$3π$)的情况中，经过一段弛豫期后，它们会快速发生向GNS的形貌转变。在AESG($3π$,$3π$)的动力学过程中，左侧和右侧的部分卷曲相互作用形成了独特的GNS，进而生成了亚稳态双卷结构。在高温扰动下，边缘折叠和卷曲向GNFs和GNSs的转变在超短时间内即可发生。值得注意的是，AESG($2π$,$3π$)演变为一种兼具折叠和卷曲结构的双态，且该过程与温度无关。
英文摘要：
Graphene-based nanofolds (GNFs) are edge-connected 2D stacked monolayers originated from single-layer graphene. Graphene-based nanoscrolls (GNSs) are nanomaterials with geometry resembling graphene layers rolled up into a spiral (papyrus-like) form. Both GNSs and GNFs structures induce significant changes in the mechanical and optoelectronic properties of single-layer graphene, aggregating new functionalities in carbon-based applications. Here, we carried our fully atomistic reactive (ReaxFF) molecular dynamics simulations to study the self-folding and self-scrolling of edge-deformed graphene sheets. We adopted initial armchair edge-scrolled graphene (AESG($ϕ$,$θ$)) structures with similar (or different) twist angles ($ϕ$,$θ$) in each edge, mimicking the initial configuration that was experimentally developed to form biscrolled sheets. Results showed that AESG(0,$2π$) and AESG(2$π$,$2π$) evolved to single-folded and two-folded fully stacked morphologies, respectively. As a general trend, for twist angles higher than $2π$, the self-deformation process of AESG morphologies yields GNSs. Edge twist angles lower than $π$ are not enough for triggering the self-deformation processes. In the AESG(0,3$π$) and AESG(3$π$,3$π$) cases, after a relaxation period, their morphology transition towards GNS occurred rapidly. In the AESG(3$π$,3$π$) dynamics, a metastable biscroll was formed by the interplay between the left- and right-sided partial scrolling in forming a unique GNS. At high-temperature perturbations, the edge folding and scrolling transitions to GNFs and GNSs occurred within the ultrafast period. Remarkably, the AESG(2$π$,3$π$) evolved to a dual state that combines folded and scrolled structures in a temperature-independent process.
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