It is known that polychromatic carbon quantum dots (CQDs) can be obtained by doping and surface modification. The layer-wise synthesis of blue and green emitting CQDs (with typical sizes between 3 and 6 nm) is described here by adding oxalic acid and by introducing polycarboxy groups. By changing the external environment, the emission of CQDs can be adjusted in the blue-green spectral region (469–527 nm) under photoexcitation at 405 nm. The findings presented here provide new directions for the reversible regulatory transformation of polychromatic CQDs. The luminescence also is affected by a variety of conditions such as surface defects, degree of polymerization, polarity of external solutions, and hydrogen bonding which is studied in some detail. Graphical abstract Schematic presentation of the blue-green fluorescent transformation of the green carbon quantum dots(G-CQDs) to blue carbon quantum dots(B-CQDs). Schematic presentation of the blue-green fluorescent transformation of the green carbon quantum dots(G-CQDs) to blue carbon quantum dots(B-CQDs).

中文翻译：

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一种利用可逆调节颜色变换制备多色碳量子点的简单方法

众所周知，可以通过掺杂和表面改性获得多色碳量子点（CQD）。通过添加草酸和引入多羧基，这里描述了蓝色和绿色发射 CQD（典型尺寸在 3 到 6 nm 之间）的逐层合成。通过改变外部环境，可以在 405 nm 光激发下在蓝绿色光谱区域（469-527 nm）内调节 CQDs 的发射。此处介绍的发现为多色 CQD 的可逆调节转换提供了新的方向。发光还受到多种条件的影响，例如表面缺陷、聚合度、外部溶液的极性和氢键，这些条件得到了详细研究。绿色碳量子点 (G-CQD) 到蓝色碳量子点 (B-CQD) 的蓝绿色荧光转化示意图。绿色碳量子点（G-CQDs）到蓝色碳量子点（B-CQDs）的蓝绿色荧光转化示意图。