Exploring the highly selective Fe(III) and Al(III) triggered “OFF-ON” ellagic acid based fluorescent sensor: Spectroscopic, structural elucidations and dual-response mechanism

Owing to the favorable efficiency and low cost, dual-response fluorescent sensors play critical roles in the development of fluorescence assay systems. In this paper, the dual-response fluorescent of ellagic acid was reported both turn-off to Fe3+ and turn-on to Al3+, as well as the effects of pH by UV–vis absorption and fluorescence emission spectroscopy. The addition of Fe3+ changed the color of the ellagic acid solution from colorless to grey-green, and the fluorescence emission was quenched. In contrast, the addition of Al3+ changed the colorless solution to light yellow, and the fluorescence emission was significantly enhanced. The coordination constants of EA to Fe3+ and Al3+ were determined to be 3.42 × 104 M−1 and 2.83 × 105 M−1, respectively, according to Job's plot. By comparing the reaction with urolithin and its derivatives, the fluorescence emission mechanism of the ellagic acid reaction with Fe3+ and Al3+ was elucidated. The detection limits of EA for Fe3+ and Al3+ were 9.80 × 10−7 and 1.90 × 10−7 M, respectively.