Although carbon dots (CDs) as fluorescent sensors have been widely exploited, multi-component detection using CDs without tedious surface modification is always a challenging task. Here, two kinds of nitrogen-doped CDs (NCD-m and NCD-o) based on soluble starch (SS) as carbon source were prepared through one-pot hydrothermal process using m-phenylenediamine and o-phenylenediamine as nitrogenous dopant respectively. Through fluorescence “on–off” mechanism of CDs, NCD-m and NCD-o could be used as a fluorescence sensor for detection of Fe ³⁺ and Ag ⁺ with LOD of 0.25 and 0.51 μM, respectively. Additionally, NCD-m could be used for indirect detection of ascorbic acid (AA) with LOD of 5.02 μM. Moreover, fluorescence intensity of NCD-m also exhibited the sensitivity to pH change from 2 to 13. More importantly, Both NCD-m and NCD-o had potential application for analysis of complicated real samples such as tap water, Vitamin C tablets and orange juice. Ultimately, the small size of NCD-m could contribute to reinforcing intracellular endocytosis, which allowed them to be used for bacteria imaging. Obviously, these easily obtainable nitrogen-doped CDs were able to be used for multi-components detection.

Graphical abstract

Strategy for synthesis of nitrogen-doped carbon dots (NCDs) and a schematic for fabrication of as-prepared NCDs for detection of Fe ³⁺, Ag ⁺ and ascorbic acid (AA).

中文翻译：

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使用基于可溶性淀粉的合成氮掺杂碳点进行简单灵敏的多组分检测

尽管碳点 (CD) 作为荧光传感器已被广泛利用，但使用 CD 进行多组分检测而不进行繁琐的表面修饰始终是一项具有挑战性的任务。在此，分别以间苯二胺和邻苯二胺为含氮掺杂剂，通过一锅法水热法制备了两种以可溶性淀粉（SS）为碳源的氮掺杂CD（NCD-m和NCD-o）。通过CDs的荧光“开关”机制，NCD-m和NCD-o可以作为检测Fe ³⁺和Ag ^{+的荧光传感器}LOD 分别为 0.25 和 0.51 μM。此外，NCD-m 可用于间接检测 LOD 为 5.02 μM 的抗坏血酸 (AA)。此外，NCD-m 的荧光强度还表现出对从 2 到 13 的 pH 变化的敏感性。更重要的是，NCD-m 和 NCD-o 都具有分析复杂实际样品（如自来水、维生素 C 片和橙子）的潜在应用果汁。最终，NCD-m 的小尺寸可能有助于加强细胞内的内吞作用，这使得它们可以用于细菌成像。显然，这些容易获得的氮掺杂 CD 能够用于多组分检测。

图形概要

^{氮掺杂碳点 (NCD) 的合成策略和用于检测 Fe 3+}、Ag ⁺和抗坏血酸 (AA)的原样 NCD 的制造示意图。