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 Cu(2+) 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 Hg(2+) and Ag(+) ions. The copper sensing film can be regenerated using 0.01M HNO3 solution. In addition to its high stability, repeatability and reproducibility, the sensor shows operational life time of 4 weeks.