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

Highlights: • A novel thiophene-based colorimetric and fluorescent turn-on sensor TS was developed for Al³⁺ and Zn²⁺ ions detection. • Sensor TS shows rapid response, remarkable sensitivity, excellent selectivity and high anti-interference capability. • Sensor TS has been used for determination of Al³⁺ and Zn²⁺ in real environmental water, food samples and test strips. • Sensor TS can be used to image intracellular Al³⁺ and Zn²⁺ in living cells. -- Abstract: 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.