Quantum dots (QDs) exhibit unique physicochemical and optical properties that are suitable for photovoltaic cells, light-emitting diodes, and optoelectronic devices; however, unlike selenium and tellurium/metal-sulfide-based QDs, graphene quantum dots (GQDs) are comparatively less toxic and biocompatible, making them promising candidates for biological applications such as bioimaging, drug delivery agents, therapeutics, and theranostics. Various synthesis techniques such as top-down and bottom-up methods along with novel green synthesis methods for the preparation of pure and doped GQDs are thoroughly discussed in this study. Physicochemical, optical, and biological properties such as size- and chemical-composition-dependent fluorescence, therapeutics, disease diagnostics, biocompatibility, and cellular toxicity are extensively studied and summarized. Finally, the prospects and potential directions of GQDs in drug delivery and bioimaging systems are discussed in regards to challenges such as the synthesis, biocompatibility, and cellular toxicity.

中文翻译：

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用于生物成像和药物输送应用的石墨烯量子点 (GQD)：综述

量子点（QD）表现出独特的物理化学和光学特性，适用于光伏电池、发光二极管和光电器件；然而，与基于硒和碲/金属硫化物的量子点不同，石墨烯量子点 (GQDs) 的毒性和生物相容性相对较低，使其成为生物成像、药物递送剂、治疗学和治疗诊断学等生物应用的有希望的候选者。本研究深入讨论了各种合成技术，如自上而下和自下而上的方法以及用于制备纯和掺杂 GQD 的新型绿色合成方法。物理化学、光学和生物学特性，例如依赖于尺寸和化学成分的荧光、治疗学、疾病诊断、生物相容性、和细胞毒性被广泛研究和总结。最后，针对合成、生物相容性和细胞毒性等挑战，讨论了 GQDs 在药物递送和生物成像系统中的前景和潜在方向。