| Summary: | 碩士 === 國立臺灣科技大學 === 化學工程系 === 106 === Graphene quantum dots (GQDs) are carbon nanocrystals with a diameter of less than 100 nm. Due to quantum confinement and edge effects, GQDs have excellent properties, including tunable PL property, good water solubility, and excellent biocompatibility. Therefore, GQDs have been widely applied in the field of fluorescence imaging, drug delivery and sensing. That is why GQDs have attracted an increasing attention. The general synthesis method can be divided into top-down and bottom-up. The method of top-down is to cut a large block into small structures such as chemical redox method and electrochemical method as well as mechanical method, etc. However, the disadvantage is that the product is not easy to control the size and shape. Conversely, bottom-up is the use of small molecules through the polymerization reaction to form a macromolecular structure, common methods such as microwave, heat and hydrothermal method, although the synthesis of quantum dots easy to control the surface structure, but involves complex procedures and high temperature process, not easy to mass production. Here, we presented a facile, energy -efficient, scalable route to synthesize GQDs by mechanochemical assisted solid exfoliations which were operated by high energy ball milling a mixture of graphite and oxidant. The average size of GQDs was about 3.03nm. They were typical blue emission with QY around 2.23%. Though changing physical parameters such as time and rotational speed, we found that they were factors to control the yield of GQDs. The yield of GQDs was proportional physical parameters. Further, we changed different reagents to explore the effect of chemical parameters. First, the pH value of oxidant effect was discussed. We found that the higher pH value of oxidant, the higher yield of GQDs. Second, we observed that the higher molar density of oxidant ions, the higher yield of GQDs. Third, we noticed that the larger ion radius of oxidant, the higher QY of GQDs. Finally, we used PL spectrum analysis to observe the PL emission of GQDs which were synthesized by high energy ball milling with different reagent as oxidant. Most GQDs possessed typical blue emission of 435 to 445nm. However, the peak of GQDs which were synthesized by high energy ball milling with K2CO3 as oxidant was red shift. This was caused by oxygen containing group and quantum confinement.
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