For the first time is reported a facile in situ synthesis of folic acid-conjugated sulfur-doped graphene quantum dots (FA-SGQDs) through simple pyrolysis of citric acid (CA), 3-mercaptopropionic acid (MPA), and FA. The as-prepared FA-SGQDs were extensively characterized to confirm the synthesis and incidence of FA molecule on the surface of SGQDs through advanced characterization techniques. Upon excitation at 370-nm wavelength, FA-SGQDs exhibited blue fluorescence with an emission band at 455 nm. While exhibiting relatively high quantum yield (~ 78%), favorable biocompatibility, excellent photostability, and desirable optical properties, the FA-SGQDs showed suitability as a fluorescent nanoprobe to distinguish the folate receptor (FR)-positive and FR-negative cancer cells. The experimental studies revealed that FA-SGQDs aptly entered into FR-positive cancer cells via a non-immunogenic FR-mediated endocytosis process. Additionally, the FA-SGQDs exhibited excellent free radical scavenging activity. Hence, these FA-SGQDs hold high promise to serve as efficient fluorescent nanoprobes for the pre-diagnosis of cancer through targeted bioimaging and other pertinent biological studies. Graphical abstract Graphical abstract

中文翻译：

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使用叶酸偶联的硫掺杂石墨烯量子点对叶酸受体阳性癌细胞进行靶向生物成像和传感

首次报道了通过柠檬酸 (CA)、3-巯基丙酸 (MPA) 和 FA 的简单热解轻松原位合成叶酸共轭硫掺杂石墨烯量子点 (FA-SGQD)。所制备的 FA-SGQD 被广泛表征，以通过先进的表征技术确认 FA 分子在 SGQD 表面的合成和发生率。在 370 nm 波长激发后，FA-SGQD 显示蓝色荧光，发射波段为 455 nm。FA-SGQDs 表现出相对较高的量子产率（~78%）、良好的生物相容性、优异的光稳定性和理想的光学特性，显示出适合作为荧光纳米探针来区分叶酸受体（FR）阳性和 FR 阴性癌细胞。实验研究表明，FA-SGQDs 通过非免疫原性 FR 介导的内吞过程适当地进入 FR 阳性癌细胞。此外，FA-SGQDs 表现出优异的自由基清除活性。因此，这些 FA-SGQD 有望通过靶向生物成像和其他相关生物学研究作为有效的荧光纳米探针用于癌症的预诊断。图形摘要图形摘要