The successful application of fluorescence immunoassays for clinical diagnosis requires stable photoluminescent materials and highly efficient signal amplification strategies. In this work, the magnetism-functionalized lanthanide MOF-on-MOF (Fe₃O₄@SiO₂@MOF-on-MOF) was synthesized through intermolecular (van der Waals) interaction-assisted growth and further homogeneous epitaxial growth, which significantly improved the fluorescence performances and uncovered the underlying mechanism. The quantum chemical theory calculation and experimental studies revealed that the introduced magnetic Fe₃O₄@SiO₂ not only endowed magnetic separation capability but also promoted fluorescence performances, which increased the energy transfer of the intersystem crossing process and suppressed the luminescence of ligands and aggregation-induced quenching. Furthermore, the plasmonic Ag/Au nanocages were developed as highly efficient fluorescence quenchers to improve the sensitivity of the fluorescence immunoassay. On the basis of the proposed differential signal amplification (DSA) strategy, the immunoassay displayed superior detection ability, with a limit of detection of 0.13 pg·mL^–1 for severe acute respiratory syndrome coronavirus 2 nucleocapsid protein. The designed magnetic lanthanide MOF-on-MOF and proposed DSA strategy give new insights into ultrasensitive fluorescence immunoassays.

中文翻译：

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磁性功能化镧系元素 MOF-on-MOF 与等离子体差分信号放大，用于超灵敏荧光免疫测定


荧光免疫分析在临床诊断中的成功应用需要稳定的光致发光材料和高效的信号放大策略。在这项工作中，通过分子间 （van der Waals） 相互作用辅助生长和进一步的均匀外延生长合成了磁性功能化的镧系元素 MOF-on-MOF （Fe₃O₄@SiO₂@MOF-on-MOF），这显着改善了荧光性能并揭示了潜在机制。量子化学理论计算和实验研究表明，引入的磁性 Fe₃O₄@SiO₂ 不仅赋予了磁分离能力，还促进了荧光性能，增加了系统间交叉过程的能量传递，抑制了配体的发光和聚集诱导的猝灭。此外，等离子体 Ag/Au 纳米笼被开发为高效的荧光淬灭剂，以提高荧光免疫测定的灵敏度。在所提出的差分信号放大 （DSA） 策略的基础上，免疫分析表现出优异的检出能力，对严重急性呼吸系统综合症冠状病毒 2 核衣壳蛋白的检出限为 0.13 pg·mL^–1。设计的磁性镧系元素 MOF-on-MOF 和提出的 DSA 策略为超灵敏荧光免疫测定提供了新的见解。