Naphthaldehyde-Based Schiff Base Chemosensor for the Dual Sensing of Cu²⁺ and Ni²⁺ Ions

In this study, a simple Schiff base sensor 1-(((4-nitrophenyl)imino)methyl)naphthalen-2-ol(NNM) has been used for chemosensing of metal ions. The metal sensing properties of sensor NNM have been investigated using UV-visible and fluorescence spectroscopic approaches. The spectral investigations revealed a red shift in absorption spectra and quenching in the emission band of the ligand molecule in the presence of Cu²⁺ and Ni²⁺ ions. The binding stoichiometry of sensor NNM for the analyte (Cu²⁺ and Ni²⁺ ions) has been investigated by the Job's plot analysis and found to be 1:1 (NNM:Analyte). The data of the Benesi-Hildebrand plot demonstrated that NNM detected Cu²⁺ and Ni²⁺ ions in nanomolar quantity. The binding insights among NNM and analytes (Cu²⁺ and Ni²⁺ ions) have been confirmed by shifted IR signals. Moreover, the reusabilty of the sensor has been investigated using an EDTA solution. In addition, the sensor NNM also successfully applied to real water samples for the identification and measurement of Cu²⁺ and Ni²⁺ ions. Hence, this system could be highly applicable in environmental and biological applications.