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.

A novel bifunctional thiophene-based Schiff base TS as a colorimetric and fluorescent turn-on sensor for rapid and simultaneous detection of Al3+ and Zn2+ ions with high selectivity and sensitivity has been developed. The sensor shows remarkable fluorescence enhancement response for Al3+ and Zn2+ 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 Al3+ and 3.0 × 10-8 M for Zn2+, whereas respective association constants are 1.16 × 104 M-1 and 2.08 × 104 M-1. With the help of fluorescence titration and Job's plot, the stoichiometric ratio of TS with Al3+/Zn2+ was determined to be 1:1. The sensing mechanism of sensor TS with Al3+/Zn2+ based on the chelation-enhanced fluorescence (CHEF) was analyzed in detail through 1H NMR titration, FTIR, HRMS and DFT studies. Moreover, sensor TS has been applied to the detection of Al3+ and Zn2+ 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 Al3+ and Zn2+ by bioimaging.