Development of novel Schiff base fluorophores for selective detection of Cu2+ ions in seawater using test strips

A novel Schiff bases of 2-((2-aminophenylimino)methyl)-3-phenyl-4(3H)-quinazolinone (3a), 2-((2-aminophenylimino)methyl)-3-(4-tolyl)-4(3H)-quinazolinone (3b), and 2-((2-aminophenylimino)methyl)-3-(4-anisyl)-4(3H)-quinazolinone (3c) were synthesized and characterized by FTIR, NMR, and elemental analysis. In an aqueous solution at pH 8, the quinazolinone derivatives (3a-c) show remarkable selectiv-ity and sensitivity towards Cu2+ ions over other common metal ions. The molar ratio plot confirms a 2:1 stoichiometry complex formation between 3a-c compounds and Cu2+. In addition, the binding constants (Kd) were calculated using Lineweaver-Burk plots and were found to be 2.45 x10(6) , 7.80 x10(4) and 4.17 x10(5) M-1 for 3a, 3b , and 3c, respectively. The detection limits were 0.04, 0.16 and 0.10 mu mol L-1 for 3a, 3b , and 3c , respectively with a good linearity in the range of 0.2-2.0 mu mol L-1. The quenching mechanism of 3a-c toward Cu2+ ions is assigned to the reverse photoinduced electron transfer. The synthesized sensors are applied to detecting Cu(2+)ions in sea water samples. The developed sensors were successfully used as test strips for fluorescence detection of Cu2+ ions.(C) 2022 Elsevier B.V. All rights reserved.

Automated summary

Novel Schiff bases were synthesized and characterized, exhibiting remarkable selectivity and sensitivity towards Cu2+ ions in aqueous solution. The complex formation between the compounds and Cu2+ ions with a 2:1 stoichiometry was confirmed, and the binding constants were determined. The synthesized sensors were successfully applied for the detection of Cu2+ ions in sea water samples.