Interface-engineered Au@ZIF-8 core–shell nanostructures for synergistic plasmonic enhancement, molecular sieving, and photocatalytic regeneration

Sensitive detection of metabolites in biofluids is fundamentally limited by surface-related challenges, including insufficient enrichment, nonspecific adsorption, and poor interfacial durability. Here, we report an interface-engineering strategy for surface plasmon resonance (SPR) biosensors based on tri-functional Au@ZIF-8 core–shell nanostructures. By integrating plasmonic enhancement, molecular sieving, and photocatalytic activity into a single interface, the architecture simultaneously addresses trade-offs between sensitivity, selectivity, and reusability. The ZIF-8 shell serves as a size-selective molecular sieve for target enrichment and protein exclusion, while the plasmonic Au core provides electromagnetic field enhancement and enables light-driven degradation of adsorbed species. Finite element simulations were employed to analyze the interfacial optical response and near-field distribution, quantitatively revealing the interplay between field confinement and molecular capture volume to identify an optimal shell thickness. This interface, integrated onto a tilted fiber Bragg grating (TFBG)-SPR platform, was validated using uric acid. The system exhibits a detection limit of 3.28 × 10 −10  M, 93.4% recovery in artificial serum, and over 92.2% signal retention after ten visible-light-driven regeneration cycles. This work establishes a generalizable, robust, and regenerable interface framework for high-fidelity sensing in complex biological environments.