A polyoxometalate-based supramolecular chemosensor for rapid detection of hydrogen sulfide with dual signals

Hydrogen sulfide (H₂S) has been verified as an important biological mediator in human physiological activities, but its rapid and accurate detection is remaining a challenge. Based on our early work, Eu-containing polyoxometalate/ionic liquid-type gemini surfactant hybrid nanoparticles fabricated by EuW₁₀O₃₆·32H₂O (Eu-POM) and 1,2-bis(3-hexadecylimidazolium-1-yl) ethane bromide ([C₁₆-2-C₁₆im]Br₂) via ionic self-assembly (ISA) strategy, we modified the hybrids with copper (II) ion and used them as a novel turn-off supramolecular fluorescence probe for H₂S immediate response. Although copper (II) ions can cause decrease of the fluorescence intensity, the probe with moderate amount of copper (II) still has a high performance in emission property. The copper (II) ion-modified supramolecular sensor (CSS) shows dual signals in the fluorescence intensity and absorbance for H₂S detection, and the detection limit is about1.25μM. Furthermore, CSS displays high selectivity for H₂S in the presence of other anions and species (e.g. Cl^-, Br^-, I^-, SO₄^2-, SO₃^2-, S₂O₃^2-, AC^-, H₂O₂, HCO₃^-, l-cysteine, homocysteine and l-glutathione), and also have potential for preferential imaging in vivo. Besides, the fluorescence quenching mechanism of CSS in the presence of H₂S was explored. CuS generated by the reaction between Cu²⁺ and H₂S was testified to act as a quencher, and the nonradiative resonance energy transfer mechanism was speculated to be responsible for fluorescence quenching. It is anticipated that the as-prepared CSS will be used as an efficient chemosensor for the rapid detection of H₂S, which is critical for the diagnosis of some diseases, e.g. Alzhermer's disease, Down's syndrome, and diabetes, etc.