A functionalized fluorochrome based on quinoline-benzimidazole conjugate: From facile design to highly sensitive and selective sensing for picric acid

Two important fluorophores (quinoline and benzimidazole) have been successfully combined to achieve a novel fluorochrome with desirable fluorescent performance in solution and solid state. This original fluorochrome exhibits not only visual fluorescence quenching toward picric acid (PA) over other nitroaromatics and common interferents, but also ppb-level (4.86 ppb) of detection limit in semi-aqueous solution. In addition, the other sensing properties such as rapid response (second-level), good environmental compatibility (pH tolerability) and sensitivity are also evidentially revealed. The dominant quenching mechanism involves a synergistic effect of inner filter effect and photoinduced electron transfer (PET), which is fully supported by spectral analysis, H-1 NMR assay, morphological studies, lifetime experiments and theoretical calculation. Noteworthily, the fluorochrome can be readily used in real water samples for quantitative determination of PA and processed as fluorescent paper or thin layer chromatography (TLC) plate for naked-eye detection, which enable itself to be functionalized as applicable PA sensor.