A simple, highly selective and ultra-sensitive “off-on-off” fluorescent chemosensor for successive detection of aluminum ion and phosphate in water samples

A simple, highly selective and ultra-sensitive “off-on-off” fluorescent chemosensor L for successive detection of Al 3+ and PO 4 3 − was synthesized and characterized. Sensor L showed a remarkable and highly selective fluorescence enhancement towards Al 3+ against other interfering cations, owing to the suppression of intramolecular charge transfer (ICT) mechanism and CH N isomerization . A good linear relationship (R 2  = 0.9974) was obtained between the fluorescence emission intensity of L and the concentration of Al 3+ (0.025–2.0 μM) with the detection limit of 3.8 nM, which is much lower than the most literature reported. And the binding stoichiometry between L and Al 3+ is 1:1 according to Job's Plot and ESI-MS. The resultant complex can be further utilized as a secondary probe for determination of PO 4 3 − with the detection limit as low as 0.56 μM. Meanwhile, the sensor L was successfully applied to detect Al 3+ in real water, illustrating that sensor L was a promising alternative route for Al 3+ detection. Additionally, the sensing mechanism of L to Al 3+ was further demonstrated in detail by IR and 1 H NMR titration experiment. The successive recognition feature of sensor L has the potential to quantitative analysis of Al 3+ and PO 4 3 − in environment samples.