Schiff base ligand modified screen-printed carbon electrode for Ni(II) detection

Abstract This research focuses on the synthesis and application of the organic Schiff base ligand N,N′-bis(salicylidene)ethylenediamine (salen), synthesized from salicylaldehyde and ethylenediamine, as a key molecular recognition element. The salen structure, featuring characteristic imine (–C=N–) and phenolic hydroxyl (–OH) functionalities as tetradentate N 2 O 2 donor sites, was confirmed using Fourier transform-infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy, establishing its structural integrity for Ni(II) chelation. The synthesized salen was subsequently used to modify a screen-printed carbon electrode (SPCE). Electrochemical impedance spectroscopy (EIS) results revealed that salen modification significantly reduced the charge transfer resistance ( R ct ) from 1231.6 Ω to 296.3 Ω, thereby enhancing electron transfer kinetics. Salen-modified SPCE demonstrated excellent analytical performance for Ni(II) detection using differential pulse anodic stripping voltammetry (DPASV), with limit of detection (LoD) was 4.86 mM, linear range of 10–100 mM ( R 2 = 0.9981), sensitivity of 18.13 μA/mM cm 2 , and good selectivity against Fe(II) interfering ions. This study highlights the pivotal role of the salen framework in developing cost-effective and efficient electrochemical sensors for environmental nickel monitoring.