Dual mode colorimetric-fluorescent sensor for highly sensitive and selective detection of Mg2+ ion in aqueous media

Abstract

A novel dual-mode colorimetric and fluorescent probe was designed and synthesized based on the reaction of 1,10-phenanthroline and 8- hydroxyquinoline, 5-(1H-imidazole [4,5-f] [1,10]phenanthrolin-2-yl)quinolin-8-ol (PHQ), for detection of Mg2+ ion. The probe was characterized by FT-IR, UV–Vis and 1H NMR techniques. The PHQ sensor displays outstanding sensitivity and selectivity toward Mg2+ over other cations via fluorescence quenching at 300 nm and color change from colorless to yellow. A very important aspect of the presented ligand is its very high fluorescence efficiency over individual precursors 1,10-phenantroline and 8-hudroxyquinoline. Addition of Mg2+ ion to PHQ led to a color change with a significant bathochromic shift in the λmax of the absorption band and made naked eye detection possible. The experimental results as performed by Job’s method revealed a 2:1 stoichiometry of PHQ/Mg2+ ratio. The sensor exhibited high selectivity and sensitivity toward Mg2+ ions in the presence of adverse anions and cations and the detection limit was found to be 33 nM 1H NMR and quantum calculations DFT and TDDFT were used to determine the type of interactions between the PHQ and Mg2+.