▎ 摘　　要

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.