This article presents for the first time an ultrasensitive localized surface plasmon resonance (LSPR) sensor system based on multimode-singlemode-multimode fiber (MMF-SMF-MMF) structure for the accurate measurement of copper (II) Ion (Cu²⁺). Citrate-stabilized Au@AgPt core-shell nanospheres (NSs) with a rough AgPt alloy outer shell were synthesized in house, and then adhered onto the sensing section of MMF-SMF-MMF structure through silane coupling agent. Finally, the Au@AgPt NSs-coated optical fiber probe surface was covered with a layer of PEI as the chelating agent for specific Cu²⁺ trapping. The detection process of Cu²⁺ is conducted by monitoring the resonance intensity variation of the transmission spectrum, which is due to the local refractive index changes result- ing from the specific interactions between Cu²⁺ in solution and PEI immobilized on the sensor surface. The proposed PEI-Au@AgPt NSs modified fiber sensor achieved an ultralow Cu²⁺ detection level down to 10⁻¹⁶ mol/L. The facile fabrication, pollution-free, high sensitivity and cost-effectiveness of the optical fiber sensor system make it rather promising for the precise Cu²⁺ monitoring in a wide range of biological application scenarios.

本文首次提出了一种基于多模单模多模光纤（MMF-SMF-MMF）结构的超灵敏局部表面等离子体共振（LSPR）传感器系统，用于精确测量铜（II）离子（Cu ²⁺）。在室内合成了具有粗糙的AgPt合金外壳的柠檬酸盐稳定的Au @ AgPt核壳纳米球（NSs），然后通过硅烷偶联剂粘附到MMF-SMF-MMF结构的传感部分上。最后，Au @ AgPt NSs涂层的光纤探头表面覆盖有一层PEI作为螯合剂，用于特定的Cu ²⁺捕获。Cu ²⁺的检测过程通过监测透射光谱的共振强度变化来进行检测，这是由于溶液中Cu ²⁺与固定在传感器表面上的PEI之间的特定相互作用导致的局部折射率变化所致。提出的PEI-Au @ AgPt NSs改性纤维传感器实现了低至10 ^-16 mol / L的超低Cu ²⁺检测水平。光纤传感器系统的制造简便，无污染，高灵敏度和成本效益使其在广泛的生物应用场景中用于精确的Cu ²⁺监测具有相当大的希望。