A sensitive electrochemical sensor for Pb2+ ions based on ZnO nanofibers functionalized by L-cysteine

Environmental pollution caused by heavy metals is a world concern, mainly because it can be accumulated in the human body, causing serious health problems. Thus, an accurate method to determine the concentration of heavy metals, lead (II) ions for instance, for water quality control is of great significance to the protection of the environment and human health. Herein, we reported the synthesis of a zinc oxide nanofibers/L-cysteine (ZnO_L-cys) nanocomposite and its use as electrodes for the electrochemical sensing of Pb2+ ions. First, ZnO nanofibers were prepared by electrospinning method followed by annealing. Then, L-cysteine was anchored into the surface of ZnO nanofibers for producing the work electrode. Square wave anodic stripping voltammetry (SWASV) was applied for the detection of Pb2+. The ZnO_L-cys modified glass carbon electrode (GCE/ZnO_L-cys) showed considerably higher response in relation to the non-functionalized ZnO nanofibers. Several optimization parameters were studied and under optimized conditions the GCE/ZnO_Lcys electrode displayed excellent sensitivity, selectivity, and stability. The limit of detection (LOD) was 0.397 mu g.L-1 in the linear range of 10-140 mu g.L-1. Also, the sensor was successfully applied for the Pb2+ ion in real samples, with recoveries of 94% and 95%. The success of electrochemical performance is a result of the high porosity of nanofibers combined with Lewis acid-base interaction of L-cysteine, making it great material for Pb2+ detection in real sample. (C) 2020 Published by Elsevier B.V.