Highly efficient detection of Cd(II) ions by a stannum and cerium bimetal-modified laser-induced graphene electrode in water

A novel laser-induced graphene (LIG) electrode modified with SnO2 and CeO2 nanoparticles (NPs) was created to detect Cd(II) ions via differential pulsed anodic stripping voltammetry (DPASV). Transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and contact angle (CA) analyses were used to characterize the physical and electrochemical properties of the electrode. Both the electrochemical activity and adsorption capacity of the carbon electrode were significantly enhanced. Due to the synergistic effects of SnO2 and CeO2 NPs, the modification enhanced the transfer of free electrons on the electrode surface, increasing the electrode sensitivity and accelerating the response speed in the detection process. The use of poly-aminobenzene sulfonic acid (p-ABSA) further increased the conductivity of the electrode. The enhanced adsorption energy and electron transfer properties of the modified electrode were also substantiated by density functional theory (DFT) calculations. Parameters such as Sn/Ce ratio, deposition time, number of polymerization cycles of p-ABSA and solution pH were optimized to determine the best detection conditions for Cd(II) ions. Under optimal conditions, our sensor showed a broad linear concentration range (0.1 ∼ 160 μg/L) with a low detection limit (0.01 μg/L). This sensor was also successfully applied for detection of Cd(II) ions in groundwater and tap water. Recovery rates ranged from 94 to 111% with a relative standard deviation (RSD) less than 6.06%. This sensor has good anti-interference ability, reproducibility and stability. Our results provide a promising sensor technique for efficient and rapid in situ monitoring of Cd(II) ions in aquatic environments.