A lead selective dimeric quinoline based fluorescent chemosensor and its applications in milk and honey samples,...

Dimeric quinoline-based Schiff base was developed (DQS) for the specific detection of Pb²⁺ ion via fluorimetry. DQS coordinates with Pb²⁺, a variation in fluorescence intensity with enhanced radical blue shift was observed due to the restriction of CN rotation, CN isomerization, and photoinduced electron transfer (PET) mechanisms. In addition, the intramolecular charge transfer (ICT) from electron-donating morpholine to phenylene diamine acceptor linked quinoline bridge is responsible for the blue-shifted fluorescence enhancement in the DQS-Pb²⁺ complex. The binding stoichiometry of DQS: Pb²⁺ (1:2) was confirmed by host-guest titration and mass spectrometry. The limit of detection (LOD) of the DQS was found to be 1.3 × 10^-7 M for Pb²⁺ ion. The DQS sensing ability of Pb²⁺ was further applied into milk and honey samples, smartphone, bio-imaging and to construct of an INHIBIT molecular logic gate.