A fast-response and high-sensitive 8-amidoquinoline-based fluorescent probe for naked-eye selective detection of Zn(II) and its photophysical and bioimaging applications

Zinc levels in living organisms and the environment are vital to human health and the environment. Therefore, rapid and highly sensitive methods for detecting Zn²⁺ are required. Herein, a novel fluorescent probe (APYQ) was synthesized by a simple Schiff base reaction. APYQ exhibited high selectivity to detect Zn²⁺ without interference from other metal ions. The limit of detection (LOD) as low as 1.87 nM, and response time as fast as 5 s. These two indicators had the best overall performance compared to other Zn²⁺ probes over the past five years. Single crystals of APYQ and APYQ-Zn²⁺ complex were successfully obtained, indicating that the fluorescence enhancement induced by the large conjugated rigid plane structure of the complex may rationalize the superb detection limit. The intramolecular charge transfer (ICT) and chelation-enhanced fluorescence (CHEF) mechanism was proposed based on Job's plot, ESI-MS, NMR titration and DFT calculation. Moreover, APYQ possessed the capability to detect Zn²⁺ in water samples and test strips in a qualitative and quantitative manner. Furthermore, APYQ has been effectively used to detect Zn²⁺ intracellularly in Hela cells. This work provides a substantially enriched probe arsenal for the detection of Zn²⁺ with high sensitivity and fast response.