A new oxadiazole-based dual-mode chemosensor: Colorimetric detection of Co2+ and fluorometric detection of Cu2+ with high selectivity sensitivity

摘要

An asymmetrical oxadiazole derivative (Sensor 1) containing one pyridine and one formyl connecting to two benzene rings on both sides of oxadiazole unit was designed and synthesized. Sensor 1 displayed selective colorimetric sensing for Co2+ and Cu2+ ions via color changes to blue and yellow from colorless in CH3CN solutions, respectively. Sensor 1 not only exhibited an instantaneous naked-eye color change and but also could be used as a convenient test kit for recognition and detection of Co2+ ions. Sensor 1 presented high colorimetric sensitivity for Co2+ with low detection limit (3.92 x 10(-6) mol/L). Sensor 1 also displayed "On-Off" fluorescent sensing for Cu2+ over a wide range of competitive metal ions and could accurately detect the existence of Cu2+ in water samples via the fluorescent quenching and color change. The fluorescence intensity of sensor 1 in CH3CN solution showed a linear response to Cu2+ in the wide concentration range of 0-40 mu M which is beneficial for quantitative analysis. The studies on absorbance and fluorescence titration, H-1 NMR spectrum and ESIMS spectra confirmed that colorimetric sensing for Co2+ and fluorescent sensing for Cu2+ are ascribed to the complex formation with the stoichiometry of 1:1 for Co2+ and 1:2 for Cu2+.