“Turn-on” fluorescent sensor for Th4+ in aqueous media based on a combination of PET-AIE effect

Previously reported fluorescent sensors for Th 4+ experienced emission quenching or generated false positive signal upon aggregate formation in aqueous media. Herein, a simple and novel thorium sensor ( CDB-BA ) based on cyanodistyrene structure was designed and synthesized, which integrated the highly emitting characteristic of AIE effect and off-on response of PET modulation for the first time to construct the “turn-on” fluorescent probe for Th 4+ . Besides excellent selectivity, CDB-BA exhibited remarkable fluorescent enhancement which was linearly related to the concentration of Th 4+ in the range of 0.25–8 μM. The detection limit was attained 0.074 μM, which was lower than that of most previously reported sensors. The mechanism of tris-chelate complex of CDB-BA with Th 4+ was confirmed by mass spectra, IR spectra and DFT calculation. The excellent Th 4+ sensing ability of CDB-BA was successfully applied to detecting Th 4+ on TLC plates, in real water samples and living-cell imaging. This work suggested that the combination of AIE and PET photophysical mechanism could offer the merits of minimized background and enhanced signal fidelity to develop novel “turn-on” fluorescent probe in complicated aqueous environment and biological research.