AIE-based ratiometric fluorescent probe for mercury ion, medium-dependent fluorescence color change and optimized...

A new AIE-based luminogen TPES, as a ratiometric fluorescence probe for mercury(II) was readily synthesized. The probe combined the advantages of the outstanding specificity of Hg²⁺-triggered deprotection reaction of thioketal and the brilliant emission of AIEgens in aggregated state. Once encountered aqueous Hg²⁺, fluorescent color of TPES in THF-H₂O (f_w = 98%) altered from blue to green rapidly, while other metal cations gave no interference to the probe. And the mechanism of this chemosensor was carefully verified by ¹H NMR analysis, FTIR and MS spectra. As expected, TPES exhibits excellent selectivity and sensitivity towards Hg²⁺ in the solid state. When using filter paper as the solid medium, the fabricated test strips could signify Hg²⁺ ions with the LOD as 1 × 10^-5 M (Hg²⁺ in aqueous solution), accompanied with a distinct emitting altered from blue to green. Furthermore, by changing the medium from filter paper to silica gel plate, a more significant fluorescence alteration from blue to yellow was achieved, and the LOD was further optimized to 1 × 10^-6 M as discerned by naked-eye.