Catching S²⁻ and Cu²⁺ by a highly sensitive and efficient salamo-like fluorescence-ultraviolet dual channel chemosensor

A highly sensitive and efficient fluorescence-ultraviolet dual channel chemical sensor H₂L based on the salamo-like bisoxime (6,6′-dimethoxy-2, 2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol) was synthesized, Cu²⁺ and S²⁻ ions can be detected respectively. For the identification of metal cations, the Cu²⁺ can quench the fluorescence intensity of probe H₂L at the excitation wavelength of 311 nm, and when the same equivalent of EDTA was added, the fluorescence intensity of L-Cu complex returned to its original intensity practically, completing the fluorescence “OFF-ON-OFF” cycle after adding the same amount of Cu²⁺ again. The mechanism was confirmed by high resolution mass spectrometry, and it was concluded that the probe H₂L and Cu²⁺ formed a complex. For the identification of anions, UV–Vis spectral identification and naked-eye recognition for S²⁻ were performed. The binding mode of the probe to the sulfur anion and the recognition mechanism were confirmed by ¹H NMR titration. In addition, the probe H₂L showed high selectivity and sensitivity to Cu²⁺ and S²⁻, the detection limits of L-Cu and L-S systems toward Cu²⁺ and S²⁻ are 46 and 25 nM respectively. In terms of application, the content of Cu²⁺and S²⁻ in different water samples (distilled water, Yellow River water and tap water) with probe H₂L was successfully tested. These results indicated that the probe H₂L can be used as a highly selective and sensitive dual channel sensor to detect both Cu²⁺ and S²⁻ ions in the environment and biological systems.