Fluorogenic sensor with dual-channel and memory-based response for Cu²⁺ and Pb²⁺ detection in water: Application to environmental water monitoring

چکیده مقاله

The synthesized N-(pyridine-2-ylmethyl)pyrazine-2-carboxamide (L) was investigated as a highly sensitive and selective fluorescent sensor for the detection of Cu²⁺ and Pb²⁺ ions. The binding affinity of the sensor was evaluated using fluorescence spectroscopy, and its detection capabilities were quantified, yielding limits of detection (LOD) of 5.73 × 10⁻⁶ and 17.40 × 10⁻⁶ M for Cu²⁺ and Pb²⁺, respectively. The binding constants (K_a) for the complexes of L with Cu²⁺ and Pb²⁺ were calculated to be 2.30 × 10⁴ M⁻¹ for Cu²⁺ and 1.10 × 10⁴ M⁻¹ for Pb²⁺, respectively. Job's plot analysis, supported by ESI-MS and IR spectroscopy, confirmed a 1:1 stoichiometric ratio of binding between L and Cu²⁺ as well as Pb²⁺ ions. Various factors influencing sensor performance, including pH, response time, and reversibility, were also examined. Competitive binding studies demonstrated the higher affinity of L for Cu²⁺ than Pb²⁺. Additionally, the analysis of real samples confirmed the practical applicability of the sensor in detecting these metal ions in environmental and biological matrices. Furthermore, functional molecular switching behavior was explored under laboratory conditions. Also, a reversible ‘Write–Read–Erase–Read’ function has been demonstrated through a feedback loop using Cu²⁺ and EDTA as two chemical inputs. © 2025 Elsevier Ltd