Tunable multicolor carbon dots (CDs) with a quantum yield reach up to 35% were generated directly from rhodamine and urea via one-step hydrothermal approach and purified through silica gel column chromatography. Transmission electron microscopy images reveal that the as-prepared CDs possess a small size distribution below 10 nm with bright blue, green, and yellow color emission, designated as b-CDs, g-CDs, and y-CDs, respectively. The in-depth investigations reveal that the multicolor emission CDs with different fraction displays fluorescence emission wavelength ranges from 398 nm (b-CDs), 525 nm (g-CDs), to 553 nm (y-CDs) which could be well modulated by controlling the amount of heteroatom nitrogen especially amino nitrogen onto their surface structures. Further experiments verify the important role of nitrogen content by using rhodamine solely or substituting urea with sulfur containing compounds as precursors to produce corresponding CDs since the performance is lower than that of urea incorporation. Theoretical calculation results also reveal that the increasing amount of amino nitrogen into their surface structures of b-CDs, g-CDs to y-CDs is responsible for reduced band gaps energy, which result in the redshifted wavelength. Benefiting from the excellent photoluminescence properties, wide pH variation range, high photo stability, and low toxicity, these CDs were employed for HClO sensing at 553 nm within the range 5 to 140 μM with a limit of detection (LOD) of 0.27 ± 0.025 μM (n = 3) and multicolor cellular imaging in HeLa cells.

Graphical abstract

中文翻译：

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氮掺杂多发射碳点的一步合成及其在 HClO 中的荧光传感和细胞成像

量子产率高达 35% 的可调谐多色碳点 (CD) 是通过一步水热法直接由罗丹明和尿素生成，并通过硅胶柱色谱法纯化。透射电子显微镜图像显示，所制备的 CD 具有小于 10 nm 的小尺寸分布，具有明亮的蓝色、绿色和黄色发射，分别称为 b-CD、g-CD 和 y-CD。深入研究表明，具有不同分数的多色发射 CD 显示的荧光发射波长范围为 398 nm (b-CDs)、525 nm (g-CDs) 到 553 nm (y-CDs)，可以很好地调制控制杂原子氮尤其是氨基氮在其表面结构上的量。进一步的实验通过单独使用罗丹明或用含硫化合物代替尿素作为前体来生产相应的 CD，验证了氮含量的重要作用，因为其性能低于尿素掺入的性能。理论计算结果还表明，b-CDs、g-CDs 到 y-CDs 表面结构中氨基氮含量的增加是导致带隙能量降低的原因，从而导致波长红移。得益于优异的光致发光特性、宽 pH 变化范围、高光稳定性和低毒性，这些 CD 可用于 553 nm 的 HClO 传感，波长范围为 5 至 140 μM，检测限 (LOD) 为 0.27 ± 0.025 μM ( g-CDs 到 y-CDs 负责减少带隙能量，从而导致红移波长。得益于优异的光致发光特性、宽 pH 变化范围、高光稳定性和低毒性，这些 CD 可用于 553 nm 的 HClO 传感，波长范围为 5 至 140 μM，检测限 (LOD) 为 0.27 ± 0.025 μM ( g-CDs 到 y-CDs 负责减少带隙能量，从而导致红移波长。得益于优异的光致发光特性、宽 pH 变化范围、高光稳定性和低毒性，这些 CD 可用于 553 nm 的 HClO 传感，波长范围为 5 至 140 μM，检测限 (LOD) 为 0.27 ± 0.025 μM (n  = 3) 和 HeLa 细胞中的多色细胞成像。

图形概要