Smartphone-Paper Sensor for Glutathione Based on a RhB@Zn-MOF Engineered via Synergistic RET and ACE for Ratiometric Detection

Glutathione (GSH), a crucial biological thiol, is a key biomarker whose abnormal levels are implicated in various diseases. The sensitive, quantitative, and on-site detection of GSH is thus urgently required in biomedical and food-safety fields. Herein, we present a rationally designed dual-emission metal-organic framework (MOF), RhB@Zn-MOF, constructed via a one-pot synthesis by encapsulating rhodamine B (RhB) within a novel Zn-MOF. The RhB@Zn-MOF functions as a high-performance ratiometric sensor for GSH through a synergistic mechanism combining resonance energy transfer and absorbance-caused enhancement. Upon GSH binding, the yellow emission of RhB at 590 nm is progressively quenched, while the blue emission of the Zn-MOF host at 490 nm is significantly enhanced. This distinct ratiometric response, as opposed to a simple turn-on signal, provides markedly improved quantification and a substantially lower detection limit (0.689 μM) compared to the pristine Zn-MOF (24.85 μM). Leveraging the dual-emission feature of RhB@Zn-MOF, we further developed a paper-based sensor for on-site detection, which was integrated with a smartphone-based portable device for real-time analysis of practical samples. This work demonstrates that the deliberate design of Zn-MOF and its functional integration with RhB provides a high-performance platform for ratiometric fluorescence sensing, expanding its applications in practical, on-the-go detection.