The particular phase transformation during graphene fluorination process
The particular phase transformation during graphene fluorination process
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石墨烯氟化过程中特殊的相变
DOI：
10.1016/j.carbon.2018.02.060
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发表时间：
2018-06-01
期刊：
影响因子：
10.9
通讯作者：
Liu, Xiangyang
中科院分区：
文献类型：
--
作者：
Lai, Wenchuan;Wang, Xu;Liu, Xiangyang
石墨烯的化学修饰对扩大其应用一直具有重要意义，但其具体过程目前尚不清楚。本文以石墨烯的直接氟化反应为研究模型，探讨石墨烯在化学修饰过程中物理化学结构的演变。像差校正的透射电子显微镜(AC-TEM)表明，直接氟化是以区域模式进行的，在石墨烯纳米片上形成了各自的芳香区和氟化区。提出了氟化区生长的“扩展模型”作为区域氟化的原因，并通过密度泛函理论计算进一步证实了这一点。膨胀模型表明，初始氟化发生在石墨烯纳米片缺陷附近，随后的氟化发生在原始氟化区附近，导致氟化反应从氟化区向芳香区扩散。这种特殊的相变过程也可以控制含氟石墨烯(FG)的结构和性能变化。更有趣的是，在一个氟化阶段就会出现所谓的“反相”现象，从而导致FG产物的某些性质，如能隙、光致发光强度或自旋中心密度等发生突变。(C)2018爱思唯尔有限公司。保留所有权利。
Chemical modifications of graphene are always significant to expand its applications, while their detailed process is still indefinable at present. Herein, the direct fluorination of graphene is regarded as a research model to explore the evolution of physical-chemical structure of graphene during chemical modification. Aberration-corrected transmission electron microscope (AC-TEM) demonstrated that the direct fluorination proceeded in a regional pattern resulting in respective aromatic region and fluorinated region on graphene nanosheet. The "expanding model" for growth of fluorinated region was then proposed as the reason of regional fluorination, which was further proved by DFT calculations. The expanding model demonstrated that initial fluorination took place close to defects on graphene nanosheet and subsequent fluorination occurred close to original fluorinated regions, resulting in the spreading of fluorination reaction from fluorinated region to aromatic region. Such a particular phase transformation process can also control the structure and property changing of fluorinated graphene (FG). More interestingly, the so-called "phase reversal" phenomenon would appear at one fluorinating stage, which thus brought about the saltation in some properties of FG products such as energy gap, photoluminescence intensity or density of spin centers. (C) 2018 Elsevier Ltd. All rights reserved.