Preparation Of N-Doped Mesoporous Carbon/Metal Oxide Composites And Electrochemical Sensing For Heavy Metal Ions

Technological development and social progress are accompanied by different environmental pollution,among which heavy metal pollution is a serious hazard to human health.To face the problem of heavy metal pollution,it is crucial to determine whether the pollution has occurred and to quantify the degree of pollution.Therefore,it is essential to develop a fast and accurate heavy metal ion detector.Electrochemical sensing has the advantages of high sensitivity,low detection limit,and brief analysis,which is suitable for applying heavy metal ion detection.Mesoporous carbon materials are used to enhance electrochemical sensing performance due to their large specific surface area and controllable structure,but they still have problems such as low conductivity and long ion diffusion paths,while nitrogen doping can introduce defects in the carbon structure and increase the conductivity while increasing its specific surface area.To further solve the shortcomings of N-doped mesoporous carbon,such as few redox reaction sites and low efficiency,in this paper,N-doped mesoporous carbon（N-MC）is compounded with metal oxides with multiple oxidation active sites to construct N-MC/metal oxide nanocomposites for use as electrode modification materials for electrochemical sensing,thereby improving the detection of heavy metal ions,as follows:（1）N-MC was synthesized from melamine-formaldehyde resin oligomer by water emulsion polymerization self-assembly.The hexagonal sheet metal oxide Ni Co₂O₄was prepared by the one-pot method and then combined with N-MC to obtain N-MC/Ni Co₂O₄nanocomposite system,which can be used to construct electrode materials for electrochemical sensing.The square wave anodic stripping voltammetry of Cd²⁺and Pb²⁺showed linear dynamic changes at the concentrations of 1-10μM and 1.5-10.5μM,respectively,when the doping ratio of the composite was 1,the supporting electrolyte was sodium citrate buffer solution,the p H value was 3,the deposition potential was-1.1 V,and the deposition time was180 s.The detection limits of Cd²⁺and Pb²⁺in solution are 0.096μM and 0.066μM,respectively.In addition,the sensors prepared in this study have been successfully applied to determine Cd²⁺and Pb²⁺in actual water samples with high stability.The N-MC/Ni Co₂O₄electrode composites prepared in this work provide a new idea for developing high-performance electrochemical sensors.（2）N-MC itself has few binding sites for the REDOX reaction of heavy metal ions.At the same time,mesoporous Ti O₂can provide a large number of active sites for the REDOX reaction of specific metal ions.Mesoporous Ti O₂was prepared by simple grinding and calcination,and then combined with N-MC to form N-MC/Ti O₂nanocomposite system,which was used to detect Cd²⁺and Pb²⁺in the solution at the same time.The influences of supporting electrolyte type,buffer solution p H value,deposition potential,and deposition time on the detection effect of modified electrode were analyzed.The experimental results show that the sensor can selectively recognize Cd²⁺and Pb²⁺,and there is a good linear relationship between the current response and the concentration of Cd²⁺in the detection range of 1-10μM.The calculated detection limit is 0.091μM.In the detection range of 1.2-10.2μM,the linear relationship between the current response and Pb²⁺concentration is good,and the calculated detection limit is 0.041μM.In addition,the presence of interfering ions(Cd²⁺,Cu²⁺,Fe³⁺,Zn²⁺,Fe²⁺,Ni²⁺and Na⁺)did not significantly affect the sensitivity of Cd²⁺and Pb²⁺.In this paper,N-MC/metal oxide nanocomposites are taken as the research object,two kinds of electrochemical sensing composites are constructed,combined with square wave anode stripping voltammetry（SWASV）to optimize the properties of the composites,and successfully realize the micro detection of heavy metal ions.