A highly selective and instantaneously responsive Schiff base fluorescent sensor for the “turn-off” detection of iron(III), iron(II), and copper(II) ions

A new and tri-responsive fluorescent Schiff base probe (DBAB) has been designed and developed for the recognition of iron(III) ions (Fe³⁺), iron(II) ions (Fe²⁺) and copper(II) ions (Cu²⁺) simultaneously. This sensor displays a favorable selectivity for Fe³⁺, Fe²⁺ and Cu²⁺ ions over a range of other common metal cations in DMF solution, leading to prominent fluorescence on–off. The detection limits were 2.17 × 10⁻⁶ M for Fe³⁺, 2.06 × 10⁻⁶ M for Fe²⁺ and 2.48 × 10⁻⁶ M for Cu²⁺ respectively. This tri-responsive fluorescent probe for Fe³⁺, Fe²⁺ and Cu²⁺ was distinguished by further reduction of the ascorbic acid. The recognition mechanism of DBAB toward Fe³⁺, Fe²⁺ and Cu²⁺ has been investigated in detail by Job plot measurements and ¹H NMR.