MOF-Integrated Plasmonic Nanostructures for Ultrasensitive SERS and Fiber-Optic LSPR Sensing: A ZIF-8@Ag Hybrid Platform for Trace-Level Detection

The development of highly sensitive and reliable optical sensors is essential for advancing molecular detection technologies. In this study, we present the development of a ZIF-8@Ag heterostructure designed to serve dual purposes as a surface-enhanced Raman scattering (SERS) sensor and a fiber-optic localized surface plasmon resonance (LSPR) sensor. This engineered heterostructure enables the ultrasensitive detection of nitrofurantoin, 4-nitroaniline, and sulfadiazine. The integration of ZIF-8 plays a crucial role in stabilizing Ag nanoparticles while enhancing analyte preconcentration through its intrinsic porosity. Simultaneously, Ag nanoparticles (NPs) provide robust plasmonic enhancement, resulting in a synergistic amplification effect. This hybrid nanostructure combined the enhancement of both electromagnetic and chemical mechanisms, which improved both detection sensitivity and signal reproducibility. Notably, the SERS sensor exhibits an enhancement factor of 5.91 × 108, enabling an ultralow detection limit of 0.646 nM for nitrofurantoin. Meanwhile, the fiber-optic sensor demonstrates outstanding sensitivity, achieving a detection limit of 1.13 × 10–10 μM for 4-nitroaniline with a detection range spanning from 10–10 to 10–5 μM. The incorporation of ZIF-8 mitigates Ag NPs aggregation and enhances substrate stability, addressing key challenges in plasmonic sensor design. These findings highlight the potential of MOF-integrated plasmonic nanostructures in advancing optical sensing platforms.