l-Glutamine-assisted synthesis of ZnO oatmeal-like/silver composites as an electrochemical sensor for Pb2+ detection

We report a green synthesis of oatmeal ZnO/silver composites in the presence of l-glutamine as an electrochemical sensor for Pb2+ detection. The synthesis was performed via the direct reduction of Ag+ in the presence of l-glutamine in NaOH. X-ray diffraction indicated that the Ag+ was completely reduced to metallic Ag. The field emission scanning electron microscopy (FESEM) and energy dispersive X-ray results confirmed an oatmeal-like morphology of the ZnO with the presence of Ag. The FESEM images showed the effect of l-glutamine on the ZnO morphology. The EIS results confirmed a significant decrease in the charge transfer resistance of the modified glassy carbon electrode due to the presence of Ag. From the differential pulse voltammetry results, a linear working range for the concentration of Pb2+ between 5 and 6nM with LOD of 0.078nM (S/N=3) was obtained. The sensitivity of the linear segment is 1.42AnM(-1)cm(-2). The presence of l-glutamine as the capping agent and stabilizer decreases the size of Ag nanoparticles and prevents the agglomeration of ZnO, respectively.