Synthesis and Evaluation of a Schiff-Based Fluorescent Chemosensors for the Selective and Sensitive Detection of Cu2+ in Aqueous Media with Fluorescence Off-On Responses.

Copper being an essential nutrient; also pose a risk for human health in excessive amount. A simple and convenient method for the detection of trace amount of copper was employed using an optical probe R1 based on Schiff base. The probe was synthesized by Schiff base condensation of benzyl amine and 2-hydroxy-1-napthaldehyde and characterized by single X-ray diffraction, 1H NMR and FTIR. By screening its fluorescence response in a mixture of DMSO and H2O (20:80, v/v) R1 displayed a pronounced enhancement in fluorescence only upon treatment with copper. Other examined metal ions such as alkali, alkaline and transition had no influence. Within a wide pH range 5-12 R1 could selectively detect copper by interrupting ICT mechanism that results in CHEF. From Job's plot analysis a 2:1 binding stoichiometry was revealed. The fluorescence response was linear in the range 1-10 × 10-9 M with detection limit 30 × 10-9 M. Association constant was determined as 1 × 1011 M-2 by Benesi-Hilderbrand plot. As a fast responsive probe it possesses good reproducibility and was employed for detection of copper in different water samples.