Selective detection of 2,4,6-trinitrophenol based on in situ-generated fluorescent Zn²⁺– Anthracene ensembles in 80% aqueous dimethyl sulfoxide

Novel in situ-generated highly fluorescent chelated Zn²⁺–anthracene (Zn²⁺•P: 1:1) complex detected 2,4,6-trinitrophenol (TNP) more selectively by a “switch-off” response with a very high Stern–Volmer quenching constant (K_sv = 3.75 × 10⁶ M⁻¹) at a 1:2 stoichiometry in 80% aqueous DMSO. The selective quenching response that occurred with TNP is due to the effective destruction of the chelated complex by efficient protonation at secondary amines, which created an effective resonance energy transfer (RET) from the anthracene unit to the TNP. Formation of a stable P²⁺•(TNP)⁻₂ ionic charge-transfer complex showed that the anthracene monomer band quenching resulted from efficient RET, accompanied by synergistic multiple hydrogen bonding, electron-rich–electron-deficient π_An–π_TNP interactions, and columbic interactions. An application was demonstrated using the biocompatible ensemble-coated hydrogel for ultraviolet-assisted naked eye sensing, and its sensing mechanism was postulated. The lowest detection limit for TNP was 3.01 × 10⁻¹⁰ M in 80% aqueous DMSO.