Research Of The Lead And Copper Ion Sensor Based On Glassy Carbon Electrode

Heavy metal ions?HMIs?may come everywhere:from waste water and gas in industrial production to batteries and pigments that are used in daily activities.HMIs are not biodegradable,and they will be gradually enriched with the food chain,which will eventually cause great harm to human health.Therefore,there is an urgent need to develop HMI sensors with high sensitivity,low detection limit,good stability,portability,easy operation,and on-site detection to achieve an efficient detection of HMIs in the environment.Among many detection methods,electrochemical analysis technology stands out in HMIs detection due to its unique advantages of portable instrument,easy operation and low cost.Stripping voltammetry is one of the most important electrochemical analysis techniques.In this process,the reductive deposition and oxidative dissolution of heavy metal ions occur at the interface between the working electrode and the solution.The specific detection of heavy metal ions is achieved through the stripping peaks generated during the oxidative dissolution.Consequently,the design of the working electrode,that is,the design of the electrode modification layer,is the research hotspot in electrochemical analysis technology.In this paper,the working electrode is designed mainly from the modification of electrode modified materials and the construction of composite electrode modification layer,so as to produce Pb²⁺and Cu²⁺sensors with high sensitivity,low detection limit and good repeatability.The main research contents include:?1?A series of monodispersed nano-spherical spinel composite oxides Mn_1-xZn_xFe₂O₄?x=0,0.2,0.4,0.6,0.8,1.0?were prepared by hydrothermal method.In this paper,Mn_1-xZn_x Fe₂O₄ nanospheres were used as electrode modified materials to construct Pb²⁺electrochemical sensors based on glassy carbon electrodes?GCE?.The effects of different Zn²⁺substitution ratios?x?on the sensor characteristics were mainly studied.Among them,the sensor with Mn_0.4Zn_0.6Fe₂O₄ nanospheres as the electrode modified material has the highest response value in the detection of Pb²⁺.Under the optimal test conditions?deposition potential of-1.0 V,deposition time of 130 s and electrolyte of 0.1 M HAc-NaAc?pH=2.0??,the sensitivity of the sensor modified with Mn_0.4Zn_0.6Fe₂O₄ and Nafion is 58.613?A/?M,with a detection limit of 0.7 nM.According to cyclic voltammetry?CV?tests,the excellent sensing performance for Pb²⁺is mainly attributed to the increased electrochemical effective area after Zn²⁺substitution,the high adsorption capacity and high specific surface area of Mn_0.4Zn_0.6Fe₂O₄ nanospheres.And the use of Nafion also improves the adsorption capacity and stability of the modified electrode.?2?The ZIF-67 material was prepared by the direct precipitation method.GCE was modified by different combinations of ZIF-67,MWCNT and Nafion to regulate the structure of the modified layer,thereby improving the sensor's sensing performance for Pb²⁺and Cu²⁺.The sensor modified with ZIF-67/MWCNT and Nafion?Nafion as a layered modification?has the biggest stripping peak current value,that is,the biggest response value for Pb²⁺and Cu²⁺.The response values for 0.6?M Pb²⁺and Cu²⁺are42.35?A and 41.14?A,respectively.In addition,the fabricated sensor displays a wide linear detection range of 1.38 nM to 5?M for Pb²⁺and 1.26 nM to 5?M for Cu²⁺with a detection accuracy of about 1 nM for both Pb²⁺and Cu²⁺.It also has good stability,repeatability and reproducibility for both Pb²⁺and Cu²⁺.The reason that the sensor modified with ZIF-67/MWCNT and Nafion has the excellent sensing performance was studied via cyclic voltammetry,electrochemical impedance spectroscopy?EIS?,square wave stripping voltammetry?SWASV?,and chronocoulometry.It can be found that the synergistic effect of ZIF-67,MWCNT,and Nafion makes the electrode modification layer?ZIF-67/MWCNT/Nafion?has catalytic ability,good electron transfer ability and heavy metal ion enrichment ability,so that the sensor has excellent sensing performance for Pb²⁺and Cu²⁺.In this paper,Mn_0.4Zn_0.6Fe₂O₄ nanospheres and a combination of ZIF-67,MWCNT,and Nafion were used as electrode modification materials.Two different GCE-based heavy metal ion sensors have been developed to achieve high-sensitivity detection of low-concentration Pb²⁺and Cu²⁺,which have good application prospects in Pb²⁺and Cu²⁺detection.