Improving Electrochemical Pb Detection Using a Vertically Aligned 2D MoS Nanofilm.

Recent advancements in MoS nanofilms have aided in the development for important water-related environmental applications. However, a MoS nanofilm-coated sensor has yet to have been applied for heavy metal detection in water-related environmental samples. In this study, a novel vertically aligned two-dimensional (2D) MoS (edge exposed) nanofilm was applied for lead ion (Pb) detection. The developed sensor showed an excellent linear relationship toward Pb between 0 and 20 ppb at -0.45 V vs Ag/AgCl using square wave anodic stripping voltammetry (SWASV) with the improved limit of detection (LOD) of 0.3 ppb in a tap water environment. The vertically aligned 2D MoS sensor exhibited improved detection sensitivity (2.8 folds greater than a previous metallic [Bi] composite electrode) with lower relative standard deviation for repetitive measurements ( = 11), indicating enhanced reproducibility for Pb detection. The vertically aligned 2D MoS layers exhibited 2.6 times higher sensitivity than horizontally aligned 2D MoS (basal plane exposed). Density functional theory calculations demonstrated that adsorption energy of Pb on the MoS side edge was much higher (4.11 eV) than those on the basal plane (0.36 and 0.07 eV). In addition, the band gap center of vertical MoS was found to be higher than the Pb → Pb reduction potential level and capable of reducing Pb. Overall, the newly developed vertically aligned 2D MoS sensor showed excellent performance for detecting Pb in a real drinking water environment with good reliability.