Novel thiophene-based colorimetric and fluorescent turn-on sensor for highly sensitive and selective simultaneous detection of Al3+ and Zn2+ in water and food samples and its application in bioimaging

Abstract A novel bifunctional thiophene-based Schiff base TS as a colorimetric and fluorescent turn-on sensor for rapid and simultaneous detection of Al 3+ and Zn 2+ ions with high selectivity and sensitivity has been developed. The sensor shows remarkable fluorescence enhancement response for Al 3+ and Zn 2+ over a broad pH range with good anti-interference capability, which accompanied with an obvious color change easily detected by naked eyes. Sensor TS can detect as low as 3.7 × 10 −9  M for Al 3+ and 3.0 × 10 −8  M for Zn 2+ , whereas respective association constants are 1.16 × 10 4  M −1 and 2.08 × 10 4  M −1 . With the help of fluorescence titration and Job's plot, the stoichiometric ratio of TS with Al 3+ /Zn 2+ was determined to be 1:1. The sensing mechanism of sensor TS with Al 3+ /Zn 2+ based on the chelation-enhanced fluorescence (CHEF) was analyzed in detail through 1 H NMR titration, FTIR, HRMS and DFT studies. Moreover, sensor TS has been applied to the detection of Al 3+ and Zn 2+ in real environmental water and food samples as well as the filter paper-based test strips. Furthermore, sensor TS has good cell-permeability and can be used to selectively sense intracellular Al 3+ and Zn 2+ by bioimaging.