Studies On High-Performance Detection Of Trace Pb²⁺ Based On Metal Oxide@PPy Arrays Electrode

In the past several decades,numerous researches have focused on the determination of heavy metal ions due to their high toxicity and nonbiodegradability.It is important to develop simple,sensitive and accurate methods for their detection in environment and water.Compared to traditional methods,electrochemical detection featured with short analytical time,low-cost,high sensitivity and easy adaptability for in-situ measurement is one of the most developed methods.In recent years,the unique properties of metal oxide for detection of heavy metal ions are attracted great interest.In this work,we report the novel synthesis of Co₃O₄ nanoneedle arrays supported on Cu foam using the hydrothermal method.Then,the conductive PPy was coated on Co₃O₄ nanoneedle arrays via a chemical vapor-phase polymerization.The morphology,composition and structure of Co₃O₄@PPy electrodes were studied.Using square-wave anodic stripping voltammetry?SWASV?,a linear range between the currents and the concentrations of Pb²⁺of 0.024 to 0.48?M with the sensitivity of85.5?A?M^-1 was obtained.The limit of detection can reach to 0.58 nM.The fabricated sensor of Pb²⁺also had good selectivity,reproducibility and long-term stability.In order to further improve the sensitivity,we creatively constructed the NiCo₂O₄ nanoneedle@polypyrrole arrays anchored on three-dimensional graphene?NiCo₂O₄@PPy/3D graphene?for detection of trace Pb²⁺.The 3D graphene was prepared by a hydrothermal process and then decorated with NiCo₂O₄ nanoneedle arrays by anoher hydrothermal process.Furthermore,the highly conductive PPy was coated on NiCo₂O₄ via a chemical vapor-phase polymerization.The free-standing NiCo₂O₄@PPy/3D graphene can be directly utilized as working electrode.High conductivity,large specific surface area,short ion diffusion path and excellent adsorption capacity of NiCo₂O₄@PPy/3D graphene improved electrochemical property for the detection of Pb²⁺.Using SWASV,a linear range of 0.0125 to 0.709?M with a high sensitivity of 115.621?A?M^-1 was obtained.The limit of detection can reach to 0.2 nM.In addition,the fabricated sensor of Pb²⁺also had good selectivity,reproducibility and long-term stability.It can be used for the simultaneous detection of Pb²⁺and Cd²⁺.Finally,NiCo₂O₄@PPy/3D graphene electrode was utilized for determining Pb²⁺in real sample using the standard addition method.