Highly selective nitrogen-doped carbon quantum dots (ND-CQDs) for copper ion (Cu²⁺) determination were synthesized by a solvent-free pyrolysis of citric acid and histidine. The resultant ND-CQDs display a stable bright blue fluorescence with a satisfactory product yield of 56% and quantum yield of 16%. The ND-CQDs not only show good photostability under continuous UV irradiation, but are also dramatically stable against extreme ionic strengths. The solid powders of the ND-CQDs re-dispersed in water still maintain a strong blue fluorescence after storing at room temperature for 6 months. The ND-CQDs can be employed to selectively detect Cu²⁺ in a wide linear range of 0.6–30 μM. The detection limit is as low as 0.19 μM. The ND-CQDs were applied for Cu²⁺ detection in environmental water samples, fruit juice samples, and urine sample. Satisfactory recoveries of 96–102% with relative standard deviations below 3% were obtained. The research provided a promising prospect for selective detection of Cu²⁺ in the complex matrix.

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通过柠檬酸和组氨酸的无溶剂热解合成了用于铜离子（Cu ²⁺）测定的高选择性氮掺杂碳量子点（ND-CQDs）。所得的ND-CQD显示出稳定的亮蓝色荧光，具有令人满意的56％的产物产率和16％的量子产率。ND-CQD不仅在连续的紫外线照射下显示出良好的光稳定性，而且在极高的离子强度下也非常稳定。在室温下保存6个月后，重新分散在水中的ND-CQD固体粉末仍保持强烈的蓝色荧光。ND-CQD可用于在0.6–30μM的宽线性范围内选择性检测Cu ²⁺。检测限低至0.19μM。ND-CQD用于Cu ²⁺在环境水样品，果汁样品和尿液样品中进行检测。获得令人满意的96-102％的回收率，相对标准偏差低于3％。该研究为复杂基质中Cu ^2+的选择性检测提供了有希望的前景。

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