Dual-ligand-functionalized gold nanoparticles on ZIF-8: A bimodal ratiometric sensor for sensitive detection of penicillin G.

Metal-organic frameworks (MOFs) provide a unique platform for tailoring the optical microenvironment of metal nanoparticles. However, simultaneously achieving high brightness, dual-emission self-calibration, and target-specific recognition remains challenging. In this sense, we prepare a dual-ligand engineered gold nanoparticle (Au NPs) system exhibiting well-resolved bimodal fluorescence. The Au NPs can be integrated with ZIF-8 via surface loading and in-situ encapsulation, respectively, yielding two kinds of composites. Comparative studies reveal that, compared to the in-situ encapsulated material (Au NPs@ZIF-8), the surface-loaded architecture (Au NPs/ZIF-8) demonstrates significantly higher quantum yield and photostability, thus enabling an optimal scaffold for sensing applications. Leveraging this, a ratiometric fluorescent probe is developed to linearly quantify penicillin G down to 0.8 nM in real samples with recoveries of 86-108 %. Notably, the dual-emission ratiometric is able to read-out mitigates matrix effects without sophisticated sample pretreatment, indicating robustness against turbidity and autofluorescence. This work proposes a new approach to fabricate high-performance ratiometric fluorescence sensors for sensitive detection of penicillin G in food and environment.