| Summary: | 碩士 === 中原大學 === 物理研究所 === 104 === Optical properties of Graphene Quantum Dots (GQDs) depend on their size, shape, edge configuration, and surface functionalities. With regards to these varieties of factors, GQDs demonstrate diverse optical characteristics. In order to employ the applicability of GQDs on different fields of science and technology, fabrication of GQDs with tunable optical characteristics is of essential. This study involves synthesis of the tunable luminescent GQDs, investigating the origin and mechanism of the photoluminescence (PL) in GQDs, and utilizing GQDs in biomedicine.
Carboxyl-functionalized multi-walled carbon nanotubes (MWCNTs) in water were used to synthesize GQDs using pulsed laser ablation (PLA). The as-fabricated GQDs with an average size smaller than 3 nm were obtained by fragmentation of MWCNTs via oxidative cutting. By controlling the PLA time, the GQDs generate tunable PL ranging from green to blue. The PL spectrum (emission energy) of the green GQDs remains unchanged under different excitation energies and simultaneously varies under different pH conditions. On the other hand, PL of the blue GQDs correlates with the excitation energy while displaying negligible change under different pH conditions. We suggest that the localized core states and delocalized edge states are responsible for emission of the blue and green GQDs, respectively. Furthermore, the GQDs were effectively utilized for cell labeling and imaging, exhibiting potential applications in biomedicine.
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