Fluorescence Enhancement of Containing‐Pyridine Polyurea and Specific Detection of Cu 2+ Ions

Non‐conjugated fluorescent polymers have attracted much attention because of their simple preparation, unique properties and wide applications. In this investigation, we designed and synthesized the non‐conjugated fluorescent polyureas (PUAs) containing pyridine structure with three diaminopyridines as the monomers according to the cluster‐triggered emission (CTE). It was found that the fluorescence of PUAs depends heavily on the intramolecular aggregation of pyridine and urea groups along macromolecular chains, and the formation of a three‐dimensional hydrogen bond network between NH and OC bonds. Among three PUAs, PUA‐34 with excellent light stability and wide spectrum excitation characteristics has high selectivity for Cu 2+ detection even in the coexistence of 14 common cations and 11 anions. The detection limit is measured as low as 0.8 μM (linear range 1–100 μM), which is significantly superior to the traditional detection methods. The UV–Vis absorption spectroscopy, fluorescence lifetime and Stern–Volmer equation evaluation together confirm the dominated static quenching by the coordination between Cu 2+ ions and urea groups. The recovery rates of PUA‐34 for detecting Cu 2+ in water samples ranged from 99.2% to 101.6% (RSD < 5%), confirming its reliability in practical applications. This work provides a simple method to prepare the non‐traditional fluorescent polyurea, which shows the potential practical applications as fluorescent probes for Cu 2+ ion detection.