In this work, a simple, continuous and completely green method based on microflow technique is demonstrated for the synthesis of carbon quantum dots (CQDs) from diverse bio-based precursors. CQDs prepared from milk is illustrated as a case study to show the process feasibility. Crystalline fluorescent CQDs of 12.53% quantum yield and good stability are synthesized by the approach, even at 120°C. Systematic experiments further suggest their optical properties, bandgap energy, and fluorescence lifetime are closely related to the synthesis temperature. The maximum production rate of the CQDs was 51.1 mg/h at 180°C. Cytotoxicity and cellular imaging tests against 3T3 cells reveal the CQDs possess high biocompatibility, and can penetrate cell membranes and display bright fluorescence. The process versatility is investigated by expanding the precursor to watermelon juice, orange juice, and soy milk, indicating successful synthesis of small-sized CQDs of low cytotoxicity and strong photoluminescence by the technique.

中文翻译：

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用于生物成像应用的荧光碳量子点的绿色连续微流合成

在这项工作中，展示了一种基于微流技术的简单、连续且完全绿色的方法，用于从多种生物基前体合成碳量子点 (CQD)。以牛奶为原料制备的 CQD 以案例研究为例，以说明工艺的可行性。通过该方法合成了 12.53% 量子产率和良好稳定性的晶体荧光 CQD，即使在 120°C 下也是如此。系统实验进一步表明它们的光学性质、带隙能量和荧光寿命与合成温度密切相关。在 180°C 下，CQD 的最大生产速率为 51.1 mg/h。针对 3T3 细胞的细胞毒性和细胞成像测试表明 CQD 具有高生物相容性，并且可以穿透细胞膜并显示明亮的荧光。