Green-emitting AIEgen for instantaneous fluorescent switch-off detection of uranyl ions in environmental water samples

Abstract

The probability of exposure to radioactive substances like uranium has increased considerably with the significant growth in the use of nuclear power in various sectors, which endangers the environment and human health. Herein, a fluorescence-based approach has been introduced for quick and accurate detection of UO22+ ions. Aggregation-induced emission (AIE) active Schiff base UFS was facilely synthesized and characterized by various spectral data. AIE behaviour of UFS in mixed DMSO-H2O medium shows a strong green emission at 520 nm when the water fraction (fw) is above 90%. The green-emitting luminogen (AIEgen) UFS in DMSO:H2O (fw = 95%) was employed for the detection of metal ions. AIEgen UFS shows selective fluorescence quenching at 520 nm with the addition of UO22+ via chelation-enhanced fluorescence quenching (CHEQ) mechanism. The complex species formed between UFS and UO22+ in 2:1 binding stoichiometry was supported by Job’s plot and mass analysis. Also, the CHEQ mechanism was complemented by density functional theory (DFT) results. The fluorescence titration experiment revealed that AIEgen UFS can detect UO22+ down to 87.3 nM. AIEgen UFS gelatin gel, coated cotton buds and paper strips were prepared for on-site visual detection of UO22+. Further, the analytical utility of AIEgen UFS was examined by quantifying UO22+ in various real environmental water samples (river water, rainwater and tap water).