Multifunctional Schiff Base Chemosensor for Cu²⁺ and 2,4-D Sensing with Potent Antibacterial Activity

A novel Schiff base chemosensor SP1, was synthesized for the detection of Cu²⁺ ions and 2,4-dichlorophenoxyacetic acid (2,4-D). The chemosensor exhibited weak fluorescence due to the photoinduced electron transfer (PET) mechanism. Upon interaction with Cu²⁺, SP1 underwent a distinct "turn-on" fluorescence response accompanied by a visible color change from yellow to orange, resulting from the formation of the SP1-Cu²⁺ complex, which inhibited the PET process. The complex was further utilized for the detection of 2,4-D, which led to fluorescence quenching and color recovery, enabling a dual-mode sensing approach. The detection limits were found to be 0.003 ppm for Cu²⁺ and 0.02 ppm for 2,4-D, demonstrating high sensitivity. Additionally, SP1 and its SP1-Cu²⁺ complex was evaluated for their antibacterial activity, showing promising efficacy against pathogenic bacterial strains. This dual-functional chemosensor offers a reliable and sensitive platform for both metal ion detection and environmental pollutant monitoring, with added antibacterial potential.