The aggregates of glutathione-capped CuNCs induced by Al3+ (named CuNCs@Al3+ complexes) show a stable aggregation-induced emission (AIE) for about 1 month. Their fluorescence maintains a high level in the pH range 4.0 to 7.0, while it quenches as pH increases from 7.0 to 7.7 or decreases from 4.0 to 3.0. Under urease-catalyzed hydrolysis, urea produces ammonia, which can be further hydrolyzed to yield OH−. This leads to a pH increase of the immediate environment. Hence, the CuNCs@Al3+ complexes are a suitable probe to determine urea. The fluorescence of CuNCs@Al3+ complexes quenches linearly at 585 nm with the excitation wavelength at 340 nm when the concentration of urea increases from 20 to 150 μM. The limit of detection (LOD) of urea is 5.86 μM. This sensitivity is superior to other reported works due to the narrow pH response range of CuNCs@Al3+ complexes. This method has been successfully applied for measuring urea in human urine samples with satisfactory recoveries. Graphic abstract Schematic representation of urea determination based on pH-responsive property of copper nanoclusters@Al3+ complexes. Ammonia is produced in the hydrolysis of urea by urease, and it is further hydrolyzed to yield OH−, leading to increasing pH of the environment. Schematic representation of urea determination based on pH-responsive property of copper nanoclusters@Al3+ complexes. Ammonia is produced in the hydrolysis of urea by urease, and it is further hydrolyzed to yield OH−, leading to increasing pH of the environment.

中文翻译：

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具有强且稳定的聚集诱导发射的铜纳米团簇@Al3+配合物在酶法测定尿素​​中的应用

由 Al3+ 诱导的谷胱甘肽封端的 CuNCs 的聚集体（命名为 CuNCs@Al3+ 复合物）显示出稳定的聚集诱导发射（AIE）约 1 个月。它们的荧光在 4.0 到 7.0 的 pH 范围内保持高水平，而随着 pH 从 7.0 增加到 7.7 或从 4.0 减少到 3.0，它会猝灭。在脲酶催化水解下，尿素产生氨，氨可进一步水解产生 OH−。这导致直接环境的pH值增加。因此，CuNCs@Al3+ 复合物是测定尿素的合适探针。当尿素浓度从 20 μM 增加到 150 μM 时，CuNCs@Al3+ 配合物的荧光在 585 nm 处线性猝灭，激发波长为 340 nm。尿素的检测限 (LOD) 为 5.86 μM。由于 CuNCs@Al3+ 复合物的 pH 响应范围窄，这种灵敏度优于其他报道的工作。该方法已成功应用于人体尿液样品中尿素的测定，回收率令人满意。图形摘要 基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。基于铜纳米团簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。该方法已成功应用于人体尿液样品中尿素的测定，回收率令人满意。图形摘要 基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。该方法已成功应用于人体尿液样品中尿素的测定，回收率令人满意。图形摘要 基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。基于铜纳米簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。基于铜纳米团簇@Al3+ 配合物的 pH 响应特性测定尿素的示意图。尿素酶水解尿素时会产生氨，氨进一步水解产生 OH−，导致环境 pH 值升高。