Oxadiazole-based selective chemosensor for copper (II) based on fluorescence quenching

- A new oxadiazole (HDOD) was synthesized as a fluorescent chemosensor for Cu2+.
- The chemosensor HDOD exhibited a highly selective fluorescence quenching towards Cu2+.
- The chemosensor HDOD had good selectivity and sensitivity to Cu2+ in aqueous solutions.
- The sensing property was monitored by UV-vis, fluorescence, NMR and MS spectroscopy.

A highly selective and sensitive oxadiazole-based chemosensor, 2-(2-hydroxyphenyl)-5-(4-dimethylaminophenyl)-1,3,4-oxadiazole, was designed and synthesized. The UV-vis absorption and fluorescence behavior between chemosensor and Cu2+ ion were investigated in 9:1 (v/v) ethanol-Hepes buffer (pH = 7.0) solution. The fluorescence of the chemosensor can be dramatically quenched by Cu2+ ion in aqueous solution, whereas it was not any interference from other metal ions such as Al3+, Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Fe3+, Hg2+, K+, Mg2+, Na+, Ni2+, Pb2+ and Zn2+. The complex formed between chemosensor and Cu2+ ion is found to be 2:1 stoichiometry with an association constant of 6.38 × 104 M−1. The detection limit for Cu2+ ion determination is 8.71 × 10−7 mol L−1. In addition, the binding mode between chemosensor and Cu2+ ion was confirmed by 1H NMR and mass spectrometry.

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