A Novel Colorimetric Fluorescent Probe for Fe3+ Based on Tetraphenylethylene-rhodamine

A novel tetraphenylethylene-rhodamine-based fluorescent probe amide compound L was synthesized and its sensing properties of metal ions were investigated. It exhibited high sensitivity and high selectivity toward Fe3+ compared with other common metal ions in EtOH-H2O (50 uM, 3:2, V/V, pH 7.0). A fluorescence quenching ratio of 92% at 482 nm and 254-fold enhancement of fluorescence intensity at 582 nm were achieved upon the addition of 4.0 equiv. Fe3+. Under optimal experimental conditions, the fluorescence intensity of probe exhibited a dynamic response range for Fe3+ from 2.0 x 10(-5) M to 1.5 x 10(-4) Mat 482 nm and 3.0 x 10(-5) M to 1.5 x 10(-4) M at 582 nm, respectively, with a detection limit of 1.56 x 10(-7) M. Meanwhile, the binding ratio of L and Fe3+ was confirmed to be 1:1 by electrospray ionization-mass spectrometry (ESI-MS) analysis of L-Fe3+ complex and Benesi-Hildebrand method. According to H-1-nuclear magnetic resonance (NMR) titration and scanning electron microscopy results, the coordination mechanism of probe L with Fe3+ was further elucidated. The binding of Fe3+ to L not only led to the aggregation state dispersed and fluorescence quenching at 482 nm, but also induced spirolactum ring opening of rhodamine and aroused a 254 times fluorescence enhancement at 582 nm together with color variation from colorless to red purple. The developed sensor was successfully employed to determine Fe3+ ion in water samples and proved to be selective and sensitive.