In this work, zinc-doped carbon dots (Zn-CDs) were anchored on a three-dimensional wheel type paper-based microfluidic chip, and were decorated with 6-mercaptonicotinic acid (MNA) and L-cysteine (L-Cys) for highly sensitive and rapid fluorescence detection of Cu²⁺. Zn-CDs were first anchored on paper through the amide bonds between the carboxyl groups of the Zn-CDs and the amino groups of the paper. Afterwards, Zn-CDs were decorated with MNA and L-Cys, effectively preventing the Zn-CDs from aggregation. The nitrogen atom on the pyridine ring and the carboxylic acid groups in MNA and L-Cys coordinated with Cu²⁺ to form a nonfluorescent ground-state complex, causing the fluorescence quenching of the Zn-CDs. The three-dimensional rotary design could simplify the operation process and achieve simultaneous analysis of multiple samples with different concentrations. Under optimal conditions, the fluorescent sensor exhibits linear response for the determination of Cu²⁺ in the range from 0.1 to 60 μg L⁻¹ with the detection limit (LOD) of 0.018 μg L⁻¹. The proposed strategy provides a novel way for the highly sensitive detection of Cu²⁺ in a complex water environment.

中文翻译：

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将掺锌碳点锚定在纸基芯片上，用于铜离子的高灵敏度荧光检测

在这项工作中，锌掺杂碳点 (Zn-CDs) 被锚定在三维轮式纸基微流控芯片上，并用 6-巯基烟酸 (MNA) 和L-半胱氨酸 ( L- Cys)修饰Cu ^{2+ 的}高灵敏度和快速荧光检测。Zn-CDs 首先通过 Zn-CDs 的羧基和纸的氨基之间的酰胺键锚定在纸上。之后，Zn-CDs 被 MNA 和L- Cys修饰，有效地防止了 Zn-CDs 的聚集。吡啶环上的氮原子和 MNA 和L -Cys 中的羧酸基团与 Cu ^{2+ 配位}形成非荧光基态复合物，导致 Zn-CDs 的荧光猝灭。3D旋转设计，简化操作流程，实现多个不同浓度样品的同时分析。在最佳条件下，荧光传感器在 0.1 至 60 μg L ^-1范围内对 Cu ²⁺的测定表现出线性响应，检测限 (LOD) 为 0.018 μg L ^-1。所提出的策略为复杂水环境中Cu ²⁺的高灵敏度检测提供了一种新方法。