The Preparation Of Transition Metal Doping ZIF-67 Nanocomposite And Its Properties Of Electrochemical Sensing

During the great progress to build China into a great modern socialist country,industrialization has made great strides,but the ensuing problem of environmental pollution is becoming more and more acute,especially the heavy metal pollution in the water environment.These heavy metal ions are not biodegradable,and will accumulate in the organism under the action of the food chain,causing harm to human and animal health and life safety.Therefore,it is very important to realize the rapid,efficient and accurate detection of heavy metal ions in water.The rapid development of electrochemical analysis technology has made voltammetry one of the reliable techniques for detecting heavy metal ions.The advent and rapid development of metal organic framework materials(MOFs)provide a new option for chemically modified electrode materials.The zeolite imidazolate framework materials(ZIFs)in MOFs has attracted much attention in the fields of energy storage,gas separation,catalysis and supercapacitor due to its rich microporous structure,extremely high specific surface area,multi-metal active sites,adjustable pore size and good thermal and chemical stability.However,due to its low conductivity and instability in aqueous solutions,ZIFs have poor electrochemical application performance.In recent years,people have adopted a variety of methods to obtain better conductivity and stability of ZIFs and its derived materials.In this paper,ZIF-67 is a precursor,and the transition metal element manganese was doped into ZIF-67 nanomaterials,which can control the preparation of Mn-ZIF-67 nanocomposites.The manganese shows strong oxidation in the high valence state,and is very stable in the low valence state.At the same time,it will produce a bimetallic synergistic effect with cobalt in ZIF-67,which effectively improves the comprehensive performance of the nanocomposite.An Mn-ZIF-67 nanocomposite modified glassy carbon electrode was used to prepare an electrochemical sensor for simultaneous detection of heavy metal ions Cd2+,Pb2+,Cu2+and Hg2+ in the water environment.Specific research contents include the following points:(1)First,ZIF-67 nanomaterials were prepared,and then Mn-ZIF-67 nanocomposites were synthesized by hydrothermal method to dope manganese.Characterization and analysis of the sample's micro-morphology,element composition,phase composition and element valence state by SEM,EDS,XRD,XPS and other characterization techniques.The results proved that the precursor ZIF-67 nanomaterial was successfully prepared,and manganese was doped into the ZIF-67 nanomaterial,and the nanocomposite retained the crystal structure of the ZIF-67 nanomaterial.(2)Modify the prepared Mn-ZIF-67 nanocomposites with different ratios to the surface of the glassy carbon electrode.By comparing the electrochemical characterization results of CV,EIS,SWASV,find the best doping ratio,and then use it for the detection of heavy metal ions Cd2+,Pb2+,Cu2+,and Hg2+.The results show that under the optimal experimental conditions,the detection sensitivity of the sensor reaches 6.97?A?M-1cm-2(Cd2+)?33.6?A?M-1cm-2(Pb2+)?29.05?A?M-1cm-2(Cu2+)?27.2?A?M-1cm-2(Hg2+),the minimum detection limits are 0.046?M(Cd2+)?0.022?M(Pb2+)?0.024?(Cu2+)?0.012 ?M(Hg2+).In the actual water sample detection,the electrochemical sensor also showed good stability.In a nutshell,doping the transition metal element manganese into the framework structure of ZIF-67 to obtain Mn-ZIF-67 nanocomposites provides new ideas for the modification of ZIFs materials.The nanocomposite material is used for electrode modification of electrochemical sensors,which enriches the application fields of ZIFs materials.