Fluorescent Sensor for Sequentially Monitoring Zinc(II) and Cyanide Anion in Near-Perfect Aqueous Media

We report a new sensor, <b>1</b>, for sequentially detecting Zn²⁺ and CN^– based on fluorescence. Sensor <b>1</b> was prepared through the reaction of 3-aminobenzofuran-2-carboxamide with 4-diethylaminosalicylaldehyde. Sensor <b>1</b> showed a selective “off–on” fluorescent response toward Zn²⁺, distinguishing Zn²⁺ from Cd²⁺. The limit of <b>1</b> (0.35 μM) for monitoring Zn²⁺ is lower than the World Health Organization (WHO) guideline (76 μM) for water available for drinking. Importantly, sensor <b>1</b> could sense Zn²⁺ in living cells and aqueous media. In addition, the resulting <b>1</b>–Zn²⁺ complex functioned as an efficient “on–off” sensor for CN^–. The mechanisms of <b>1</b> for detecting Zn²⁺ and CN^– were explained by spectroscopic, spectrometric, and theoretical studies