A highly sensitive, single selective, real-time and "turn-on" fluorescent sensor for Al³⁺ detection in aqueous media

A "turn-on" fluorescent sensor, sodium 4,4′, 4′′-(1H-pyrrole-1,2,5-triyl)tri-benzoate (Py(PhCOO-Na)₃), has been prepared for the detection of Al³⁺ in aqueous solution. The detection mechanism, as well the mechanism specific to Al³⁺, was studied by fluorescence spectroscopy, UV-vis spectroscopy and dynamic light scattering (DLS) measurement. Py(PhCOONa)₃ exhibited an aggregation-induced emission (AIE) characteristic and was found to show a specific affinity to Al³⁺, as indicated by the enhanced and bathochromically shifted emission of the AIE fluorogen. Upon binding Al ³⁺, a significant fluorescence enhancement with a turn-on ratio of over 10-fold was triggered by the AIE process. Moreover, this sensor is highly selective for Al³⁺ over other metal ions with a detection limit of 5 μM and a quantitative detection range of 5-120 μM, and is able to be used in the determination of Al³⁺ in drinking water. The time-response investigation indicates that the emission intensity of (Py(PhCOO ^-)₃) can be quickly boosted to reach the maximum intensity in less than 10 s upon titration of Al³⁺.