Stable Eu³⁺/Cu²⁺-Functionalized Supramolecular Zinc(II) Complexes as Fluorescent Probes for Turn-On and Ratiometric Detection of Hydrogen Sulfide

Fabrication of dual-emitting materials for H2S sensing under environmental and biological conditions is currently of great interest. In this work, a new chemically stable metal supramolecular complex [Zn2(pda)2(H2O)3]·(H2O)0.5 (Znpda, pda = 1,10-phenanthroline-2,9-dicarboxylic acid), with accessible uncoordinated carboxylic oxygen sites, is solvothermally synthesized. It can serve as a host in luminescent hybrid composites. By incorporating Eu3+ and Cu2+ in the supramolecular coordination network, we obtained the dual-emitting hybrid material Eu3+/Cu2+@Znpda, which simultaneously shows intense ligand and weak Eu3+ emissions in HEPES buffer solution. Since H2S can easily chelate with Cu2+ and recover the blocked “antenna effect” between the ligand and Eu3+, Eu3+/Cu2+@Znpda possesses both the turn-on and ratiomectric fluorescence response to H2S. Accordingly, we designed an IMPLICATION logic gate for H2S recognition by employing the fluorescence intensity ratio between the ligand and Eu3+ as the output signal. In addition, Eu3+/Cu2+@Znpda shows a fast response (<1 min) and high sensitivity (1.45 μM) to H2S over other interfering species in the HEPES buffer solution, highlighting its potential use for H2S sensing under environmental and biological conditions.