A one‐step solvothermal method for the preparation of carbon dots with red fluorescence (R‐CDs) was put forward, in which sodium citrate and formamide were chosen as precursors, while formamide was adopted as the solvent. The fluorescence emission peak of the as‐prepared R‐CDs remained the same (600 nm) when the excitation wavelength increased from 490 nm to 560 nm, and the fluorescence quantum yield is 35.3%. Furthermore, the fluorescence intensity of the as‐prepared R‐CDs could be selectively quenched by copper ions, and the mechanism of Cu²⁺ quenching R‐CDs is the combination of static and dynamic quenching. As a result, the R‐CDs were applied for the construction of a fluorescent sensor without any modification for the quantitative and visual detection of copper ions, which is a typical contaminant in water. The limit of detection for the fluorescent sensor was as low as 5 nmol/L, and it can be used to fast and directly confirm whether the content of copper ions in drinking water meets the criteria of the United States Environmental Protection Agency and the World Health Organization.

中文翻译：

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一步制备红色发光碳点，用于视觉和定量检测铜离子

提出了一种一步溶剂热法制备具有红色荧光的碳点（R-CDs）的方法，其中以柠檬酸钠和甲酰胺为前体，而以甲酰胺为溶剂。当激发波长从490 nm增加到560 nm时，所制备的R-CD的荧光发射峰保持不变（600 nm），并且荧光量子产率为35.3％。此外，所制备的R-CD的荧光强度可以被铜离子选择性淬灭，并且Cu ²⁺的机理R-CD淬灭是静态和动态淬灭的结合。结果，R‐CD被用于构建荧光传感器，而无需对铜离子（在水中的典型污染物）进行定量和视觉检测进行任何修改。荧光传感器的检出限低至5 nmol / L，可用于快速，直接确认饮用水中铜离子的含量是否符合美国环境保护署和世界卫生组织的标准组织。