Electrochemical Sensor For Heavy Metal Ions Detection By Glassy Carbon Electrode Modified With Metal-oxide Composites

The rapid development of society has also caused a series of environmental problems,in which heavy metal ions pollution in water has attracted great attention.Cu?II?,Pb?II?and Cd?II?are very common heavy metal ions,which can cause serious negative effects on the body.Therefore,the rapid detection of metal ions has become an important problem to be solved in the world.Some conventional metal ions detection methods generally need to rely on expensive and complex instruments and consume a lot of time and manpower,which are inconvenient to operate,and cannot achieve the purpose of real-time online detection,However,the electrochemical detection method has become one of the most economical and commonly used metal ion detection methods at present due to the advantages of low cost,high sensitivity and good portability.The selection of electrode modified materials is particularly important in the detection of heavy metal ions using electrochemical methods.With the rapid development of nanotechnology,tin,gold,platinum and other metal oxides have been widely used in the rapid detection of heavy metal ions because of their unique physicochemical properties,but they generally have the disadvantages of complex synthetic methods and high consumption cost.This study combine the two-dimensional layered materials graphene with excellent electrical conductivity and molybdenum disulfide?MoS₂?with metal oxides such as manganese oxide?MnO₂?and zinc oxide?ZnO?with excellent adsorption properties based on the principle of economic simplicity,three new electrochemical sensors for metal ion detection have been constructed and successfully applied to high sensitivity and anti-interference detection of trace metal ions in water.The specific work of this article is as follows:?1?The two-dimensional nanocomposite GO/MnO₂ was prepared by a simple liquid-phase synthesis method and used as an electrode modification material.The electrochemical performance of GO/MnO₂/GCE was characterized by cyclic voltammetry and electrochemical impedance,confirming the excellent electrochemical performance of GO/MnO₂/GCE.In addition,the important factors affecting the sensitivity of the sensor,including pH,deposition potential,deposition time and material proportion,were systematically investigated using the square-wave anode dissolution voltammetry?SWASV?.Under the optimal conditions,the linear range of GO/MnO₂/GCE for Cu?II?and Pb?II?was 0.005?1?M and 0.01?1?M,respectively.The detection limits were 1.67nM and 3.33 nM,which were much lower than the electrochemical detection method in the literature.Subsequently,a series of interference,stability and reproducibility tests were performed,which showed good results.An interesting interference phenomenon was observed in the detection test for mutual interference of the two target ions Cu?II?and Pb?II?:when Cu?II?and Pb?II?are present in the electrolyte simultaneously,two peeling peaks of Pb?II?are observed;when only Pb?II?is present in the electrolyte,only one peeling peak of Pb?II?can be observed.Finally,real water samples were subjected to detection,standard addition of Cu?II?and Pb?II?at different concentrations was carried out and the addition recovery was determined.It was found that the addition recovery of Pb?II?and Cu?II?at the modified electrode was between 95.25%and 100.75%,demonstrating that this work provides a novel,simple and rapid electrochemical detection method for simultaneous determination of trace metal ions Cu?II?and Pb?II?in water.?2?The two-dimensional nanocomposite rGO/ZnO was prepared by a simple hydrothermal reaction synthesis method and used as an electrode modification material for electrochemical detection of Cd?II?and Pb?II?ions in water.After the modification of ascorbic acid,the surface oxygen-containing group of GO was reduced,and the electron transport rate was greatly improved.ZnO with excellent adsorption properties was combined into the layered structure of reduced graphene oxide,which provided more active sites for the adsorption of metal ions.Under the optimal detection conditions,the detection ranges of Cd?II?and Pb?II?were 0.01?1?M and 0.005?1?M,respectively,with detection limits of 3.33 nM and 1.67 nM,which are much lower than those of some materials reported in the literature.The fabricated sensors have also been successfully applied to the detection of real samples and experiments showed that the addition recoveries of this modified electrode for different concentrations of Pb?II?,Cd?II?were between 92%and 114%.Because of its green economy preparation method and considerable electrochemical behavior,the prepared sensor has a broad application prospect in environmental monitoring.?3?The nanoflower-like composite MoS₂/MnO₂ was prepared by hydrothermal method,which showed a good adsorption effect for metal ions Cd?II?,Pb?II?.The nanomaterial was used as electrode modified material and the metal ions Cd?II?,Pb?II?was selectively detected by square wave anodic dissolution voltammetry.The sensitivity and detection limits of MoS₂/MnO₂/GCE for Cd?II?and Pb?II?were 44.17?A/?M,16.67nM and 62.96?A/?M,16.67 nM respectively.Under the optimal detection conditions,MoS₂/MnO₂/GCE has a good effect on the anti-interference,stability and reproducibility of the two kinds of ion detection,and the recovery rate of addition of Cd?II?and Pb?II?in real water samples is 90%?108.1,96%?106.2%,respectively,which can indicate that the MoS₂/MnO₂ modified electrode has good practical application value and provides a new research idea for the preparation of new heavy metal ions electrochemical sensors.