CuNCs modified with dual-ligand to achieve fluorescence visualization detection of Tin (Ⅳ)

In this study, polyvinylpyrrolidone (PVP) supported and cysteine (Cys) modified copper nanoclusters (Cys-PVP-CuNCs) with high fluorescence intensity have been synthesized and used to establish a simple and sensitive assay for the determination of trace Sn4+. The presence of Sn4+ can lead to fluorescence quenching based on the aggregation of PVP-CuNCs caused by the coordination of Sn4+ and oxygen atoms. For Cys-PVP-CuNCs, the ligand Cys can transfer electrons to the metal center of the cluster, resulting in strong fluorescence enhancement of CuNCs and intensification of fluorescence quenching after interaction with Sn4+, which is conducive to more sensitive visual detection. The proposed assay allows for the detection of Sn4+ in a linear range from 5 μg L−1 to 100 μg L−1, with a detection limit as low as 4.5 μg L−1 at a signal-to-noise ratio of 3. Moreover, under UV light, the obvious fluorescent color change can be observed by naked eyes at Sn4+ concentration ranging from as low as 5 μg L−1 to 200 μg L−1. Benefiting from the high sensitivity of this assay, satisfactory test results have been obtained when using only 10 mg of canned food samples with rapid digestion. The proposed Cys-PVP-CuNCs fluorescent probe shows excellent stability, simple operation, good selectivity, and high sensitivity, and thus it is expected to be used in the real-time field detection of Sn4+.