Highly sensitive upconversion fluorescence detection of glutathione using lanthanide-doped nanoparticles coated with MnO2

To improve the quantitative detection sensitivity of glutathione (GSH) by upconversion fluorescence, composites of lanthanide-doped upconversion nanoparticles (UCNPs) coated with a manganese dioxide (MnO₂) energy acceptor have been designed and prepared. Compared to the assemblies of MnO₂ nanosheets embedded with UCNPs, MnO₂ in closely packed structures acts as a more effective and efficient bursting agent for UCNPs to seal them properly in their luminescence off state. In the presence of GSH, MnO₂ is reduced to Mn²⁺ and this process provides an opportunity to recover the fluorescence intensity of UCNPs, which becomes more pronounced with the contribution of both internal filtration effects and fluorescence resonance energy transfer mechanisms. Under the optimized conditions, the quantitative sensing of GSH is achieved in the detection range of 0.40 μM to 116.00 μM, with a limit of detection of 31.2 nM and good selectivity.