Lead ions (Pb2+) Electrochemical Sensors Based on Novel Schiff Base Ligands

In this study, two novel bidentate Schiff base ligands, namely the (1 E,1'E,2E,2'E)-N,N'-(butane-1,4-diyl)bis(3-(2-methoxyphenyl)prop-2-en-1-imine) (L1) and the tetradentate Schiff base ligand namely N1,N2-bis(2-(((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)amino)ethyl)ethane-1,2-diamine (L2), were successfully synthesized through a simple procedure. The synthesized Schiff base ligands were characterized by Scanning Electron Microscopy (SEM) analysis, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV-Vis) spectroscopy. Moreover, the thermal behavior was studied through thermogravimetric (TG)/differential thermal gravimetric (DTG)/differential thermal analyses (DTA) analyses under nitrogen atmosphere. Subsequently, the synthesized ligands (L1, L2) features and performances as electrochemical sensors for the detection of heavy metal ions (HMIs) have been investigated. A different behavior was noticed using these two ligands, with L1 which demonstrated to be the best candidate for developing a modified screen-printed carbon electrode (L1/SPCE) electrochemical Pb2+ sensor. To improve further the performances, gold nanoparticles (AuNPs) were depositated by an electrochemical process on the L1/SPCE platform. The developed AuNPs-L1/SPCE sensor displayed enhanced lead ion sensing with a high sensitivity of 56.78 μA μM-1 cm-2 and a detection limit of 0.298 μM. This novel sensor demonstrated promising performances for the detection of Pb2+ ions in real seawater with no sample treatment.