A novel phthalohydrazide derivative as a multi-targeted fluorescent probe for monitoring trace Co2+ and Cu2+ in water

Real-time monitoring of metal ion species and concentrations in water is a highly active research field. In the paper, a novel fluorescent molecule, (E)-N'-((5-(9-phenyl-9H-carbazol-3-yl) thiophen-2-yl) methylene) terephthalohydrazide (PCTMT), is synthesized via Suzuki reaction and Schiff-base reaction in turn. In the DMF-H₂O (70 % v/v) solvent system, the PCTMT presents a good aggregation-induced enhancement (AIE) fluorescent effect and good selectivity and anti-interference for monitoring Co²⁺ and Cu²⁺ in water with a wide pH range. The probe's detection limit (LOD) reached 28.2 nM and 38.7 nM for Co²⁺ and Cu²⁺, respectively. The binding constants between PCTMT and Co²⁺ and Cu²⁺ are calculated as 1.8 ×10¹⁷ M^-2 and 2.3 ×10¹⁶ M^-2, at a 2:1 mol ratio. In the probe system, Co²⁺ and Cu²⁺can be distinguished by oxalate titration. The detection mechanism is discussed through testing analyses with the theoretical simulation calculation via the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The probe also indicates good detection capacities in real water samples. This study may promote the development of coordinated-type ion probes and innovation in water quality detection technology.