Glycyl-L-phenylalanine peptide based Schiff base dual ion selective fluorescent chemosensor: Synthesis, detection of Zn and Al, real water sample analysis and DFT study.

A glycyl-L-phenylalanine peptide-based Schiff base (HL) fluorescence probe was designed, synthesized, and characterized using various analytical techniques. The chemosensing ability of the Schiff base was explored against different metal ions. The chemosensor probe exhibited high selectivity and sensitivity towards Zn and Al ions, with detection limits of 1.63 × 10 M and 1.25 × 10 M, respectively. Job's plot analyses and the Benesi-Hildebrand relation clearly revealed a 1:1 stoichiometry between the fluorescent probe and the metal ions, with apparent binding constants of 1.02 × 105 M for Zn and 2.39 × 105 M for Al. The emission intensity of HL remained reversible over four cycles of sequential alternate additions of Al or Zn ions and EDTA, demonstrating an efficient "off-on-off" fluorescence response. The compound HL represents a tunable system incorporating one OR and one INHIBIT logic gate with two distinct sets of inputs: (i) Zn (IN1) and Al (IN2), and (ii) Zn/Al (IN1) and EDTA (IN2), with fluorescence emission as the output. Additionally, an IMPLICATION logic gate was achieved using Zn (IN1), Al (IN2), and EDTA (IN3) as inputs. Moreover, the probe demonstrated excellent potential for the quantitative detection of Zn and Al in real water samples across a wide pH range. The optimized molecular geometries and HOMO-LUMO energy gaps of the compounds (HL, HL-Zn, and HL-Al) were determined using Density Functional Theory (DFT) calculations.