Facile synthesis of guanidyl-imidazoline as “Turn-on” Zn2+ fluorescent probe with excellent sensitivity and selectivity in aqueous environment

• A water-soluble fluorescent probe was developed and used to detect zinc ions in aqueous environment. • The probe exhibited high sensitivity and strong anti-interference ability towards other metal ions . • The fluorescent probe can be applied to detect Zn ions in tap water and exhibit strong green fluorescence in cell imaging . In this work, a water-soluble guanidyl-imidazoline ( G ) was synthesized and used as a fluorescent probe to detect Zn 2+ in an aqueous environment without any mutually soluble organic solvent. G demonstrates excellent selectivity for Zn 2+ and strong anti-interference ability against other metal ions. It has an ultra-low detection limit of 25 nM for Zn 2+ ions, surpassing previously reported achievements. Job’s plot method, FTIR and XAFS revealed the binding mode of the G -Zn complex that the N atom in the G coordinates with Zn 2+ in a ratio of 2:1. Furthermore, this probe was successfully utilized for quantitative detection of Zn 2+ ions in tap water and synthetic water, and also applied to imaging Zn 2+ ions in living cells.