Effect of contact metamorphism on coal-based graphene quantum dots
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    Abstract:

    Coal is a kind of sedimentary rock seriously affected by geological action, and its properties will have a profound impact on the properties of carbon-based materials. In order to explore the influence of contact metamorphism on the properties of coal-based graphene quantum dots, coal formed in plutonic metamorphism and regional magmatic metamorphism was selected for comparison to explore the difference in properties of prepared products. Meththods: Preparation of coal-based graphene quantum dots by oxidative exfoliation method. Graphene quantum dots were obtained from deashed coal by ultrasonic, acid bathing, neutralization, dialysis and drying processes. The structures of raw coal and prepared products were analyzed by X-ray diffraction(XRD), Raman spectroscopy(Raman), Transmission electron microscopy(TEM), X-ray photoelectron spectroscopy(XPS) and Fluorescence spectroscopy(PL). Results: With the increase of coal rank, the structural defects of deashing coal decrease, the aromatic structure increases gradually, and the crystal structure proceeds in the direction of ordering. The particle size uniformity of quantum dots prepared with coal as carbon source is good, and the particle size tends to be larger with the increase of coal rank. Carbon element is mainly in the form of C-C / C-H, and oxygen mainly exists in carbon and oxygen functional groups, C∶O ≤ 7∶3, and the oxygen content increases with the increase of coal rank. In ultraviolet light (λ= Under the irradiation of 297 nm), the sample emits blue fluorescence, and the fluorescence intensity is higher in lower rank coal and gradually decreases with coal rank increasing. Compared with coal formed by plutonic metamorphism and regional magmatic metamorphism, the thermal coal formed by contact metamorphism has more COO- structure, and the content of C = O bond decreases; The rising trend of fluorescence intensity is more obvious when the coal rank is lower, and reaches the maximum in high rank bituminous coal; The coal affected by contact metamorphism has a more regular graphitization structure. Conclusions: Coal formed by contact metamorphism can be used to prepare graphene quantum dots, and the prepared products have higher aromaticity, greater ductility and smaller interlayer spacing, and show higher graphitization degree. At the same time, the prepared graphene quantum dots have good uniformity, larger size than other metamorphism, and are arranged in a more regular and orderly aromatic structure. With the deepening of metamorphism, the C-C ratio of the prepared products gradually decreases, and more O elements are doped into the quantum dot structure.

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FAN Jiangtao, TANG Yuegang, SONG Xiaoxia, WANG Shaoqing, LI Ruiqing, DONG Min.2022. Effect of contact metamorphism on coal-based graphene quantum dots[J]. Geological Review,68(4):2022072015.

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History
  • Received:January 20,2022
  • Revised:July 06,2022
  • Adopted:
  • Online: July 19,2022
  • Published: July 15,2022