RESUMO
Phosphate (Pi) plays an essential role in aquatic ecosystems as well as in physiological processes. Here, a dual-emission probe for the sensitive, specific and visual analysis of Pi is fabricated by coordinating Eu3+ with luminol and 2,6-pyridinedicarboxylic acid (DPA). Pi can significantly enhance the characteristic fluorescence of Eu3+ at 615 nm by promoting energy transfer from DPA to Eu3+ and reducing the quenching effect of water molecule, luminol with inherent emission at 423 nm further enhances the Eu3+ fluorescence. Accordingly, ratiometric detection of Pi can be achieved with the fluorescence ratio F615/F423 as a function of Pi concentration. Linearity between F615/F423 and Pi concentration in the range of 0.1-25 µM is shown, and the limit of detection (LOD, 3σ/K) for Pi is 0.027 µM. In addition, a continuous change in the fluorescence color of the probe from blue to red is observed with increasing Pi concentration under a UV lamp, and a smartphone-based visual method is used for the convenient and effective semi-quantitative determination of Pi. The dual-emission probe has been successfully applied to ratiometric and visual analysis of Pi in human urine and environmental water samples, and adequate results are obtained.