A quinoline-based fluorescent chemosensor for palladium ion (Pd2+)-selective detection in aqueous solution

Quinoline-based fluorescent chemosensors have been extensively developed for various metal cations, but it was still rare for Pd²⁺-selective detection. In this work, a novel quinoline-benzimidazole conjugate containing one carboxylic acid group (QBM) was designed, and the QBM displayed highly selective fluorescence quenching response towards Pd²⁺ over other metal cations in aqueous solution. The fluorescence titration revealed a good linear relationship between the fluorescence intensity and the Pd²⁺ concentration in the range of 0.5-10 μmol L^-1, with the detection limit of 0.26 μmol L^-1 (S/N = 3). Fluorescence detection of Pd²⁺ in practical water sample was also successfully achieved.