A dual emission ratiometric fluorescent probe constructed based on MOF-embedded dye for sequential detection of Al3+ and PPA

The ratiometric fluorescence probe has a self-calibration system that greatly reduces interference from the external environment, it has high sensitivity and accuracy in qualitative and quantitative experiments. In this work, a novel ratio fluorescence probe (RhB@1) was constructed by enclosing Rhodamine B (RhB) in the channel of [Cd₂(H₂L)₂(1,4-bib)₂]•DMA (H₂L=2-hydroxyterephthalic acid, 1,4-bib=1, 4-bis (imidazol-1-ylmethyl) benzene). The probe can display dual emission characteristics under a single excitation. Al³⁺ ion was detected by RhB@1. The results showed that the fluorescence of 1 in RhB@1 was increased, the fluorescence of RhB is unchanged, and limit of detection (LOD) of Al³⁺ is as low as 20 .9nM. Interestingly, when PPA (phenylpyruvic acid) is added to the mixture of RhB@1 and Al³⁺, PPA competes with RhB@1 for Al³⁺ result in achieving continuous ratio sensing of Al³⁺ and PPA, and LOD of PPA is 3 .21nM. More importantly, the response of RhB@1 to Al³⁺ in tap water and PPA in artificial urine was quantitatively determined by label recovery method. The results showed that the recovery rate were 97.706 %–99.060 % (Al³⁺) and 94.732 %–98.100 % (PPA). In addition, we prepared a portable test paper modified with carboxymethyl cellulose. This test paper has obvious color change when detecting Al³⁺ under ultraviolet light, which is easy to detect Al³⁺ by naked eye.