Detection Of Heavy Metal Ions By Composite Modified Electrodes

Environmental pollution caused by heavy metals occurs frequently due to the rapid development of modern industry,becoming a great threat to human health.Therefore,the effective and sensitive detection of heavy metal has become an emergent issue.Among the various heavy metal detection techniques,electrochemical detection is an efficient,sensitive and simple method.It can be used to detect of trace heavy metals with overcoming the non-real-time detection of traditional detection methods due to high requirements for experimental operating conditions.The sensitivity of an electrochemical sensor is closely related to the ability of the modified electrode material to accumulate the target heavy metal ions.Therefore,it is particularly important to choose a modified electrode material with high sensitivity,non-toxicity and harmlessness.In this work,two kinds of composite modified electrodes are prepared for detection of Pb²⁺and Cu²⁺,focusing on improving the sensitivity,selectivity of electrode materials and reducing the detection limit.（1）We prepared an electrode modified by multiwalled carbon nanotubes（MWCNTs）/Nafion composites for detecting Pb²⁺with high sensitivity and low detection limit,MWCNTs/Nafion composites were prepared by the drop casting method and Nafion was used as the dispersant and binder of MWCNTs to improve the solubility of MWCNTs.The current peak of Pb²⁺detection by MWCNTs/Nafion composite electrodes is 11.39 times higher than that detected by the bare electrodes.The parameters of the preparation and detection process of MWCNTs/Nafion composite electrode were optimized.Under the optimal preparation and detection conditions,differential pulse stripping voltammetry was used to detect Pb²⁺in the concentration range of 10³50μg/L.The detection limit of the prepared sensor was 0.0928μg/L.The repeatability of the electrode was tested,obtaining an relative standard deviation of4.75%,suggesting that the electrode can be used repeatedly.The sensor was applied to detect water samples in Liaohe River,showing that the composite electrode has excellent sensitivity and repetition rate and is promising for the detection of actual water samples.（2）In order to fabricate a high-selectivity,high-sensitivity,and low detection limit composite modified electrode for Cu²⁺,we prepared an electrode modified with Au nanoparticles（AuNPs）/graphene oxide（GO）composite.The composite is prepared by the electrochemical method.Surface morphology characterization shows that AuNPs form a three-dimensional dendritic structures along graphene,which greatly increase the specific surface area of the electrode material.The detection conditions of the AuNPs/GO/GCE were optimized.Under the optimal parameters,differential pulse stripping voltammetry was used to detect Cu²⁺in the concentration range of 10¹00μg/L.The detection limit of AuNPs/GO/GCE sensor was0.148μg/L.The AuNPs/GO composite modified electrode was successfully applied to the detection of Cu²⁺in campus rivers,demonstrating that this modified electrode has high specificity and selectivity.