Characterization of a sensitive and selective copper optode based on β-ketoimine modified calix[4]arene derivative

In this paper, an optical sensor was proposed for sensitive determination of copper (II) ions in aqueous solution. The sensing membrane was prepared by coating β-ketoimine calix[4]arene derivative as ionophore on a glass plate surface. Thin β-ketoimine calix[4]arene layer was characterized by contact angle measurements showing a good surface coverage. Besides, a smooth and homogeneous morphology of the calixarene membrane was examined by atomic force microscopy (AFM). The response of the optode is based on the decrease in the absorbance signal at 309 nm upon exposure to buffer solutions containing Cu²⁺ ions. At a pH 6.8, the proposed sensor displays a calibration response for copper over a wide concentration range of 1.0 × 10⁻⁷ M to 1.0 × 10⁻⁴ M with a detection limit of 2.0 × 10⁻⁸ M and response time of 7–10 min. This optode exhibits good selectivity toward copper ions in comparison with common ions including Hg²⁺ and Ag⁺ ions. The copper sensing film can be regenerated using 0.01 M HNO₃ solution. In addition to its high stability, repeatability and reproducibility, the sensor shows operational life time of 4 weeks. - Highlights: • Optical sensor for Cu²⁺ ion based on β-ketoimine calix[4]arene was developed. • Sensing mechanism involved the formation of a complex between calixarene and Cu²⁺. • Satisfactory analytical sensing characteristics for determining Cu²⁺ were obtained