Preparation And Application Of Iron-based Nanomaterials As Peroxidase Mimics

Nature enzyme possesses excellent catalytic activity and highly selective,but the shortcoming of high cost,complicated preparation,easy denaturation and inactivation limit its application.Nanomaterials as mimetic enzymes possess serveries of advantages,such as good catalytic stability,low expensive,easy preparation and storage.And those nanomaterials have attracted the attention of many scholars.In recent years,iron-based nanomaterials,such as iron oxide nanomaterials,iron sulfide,iron phosphate,Prussian blue and their cyanometallate structural analogues have also exhibit satisfactory enzyme-like activity.In this work,iron-based nanomaterials were prepared by hydrothermal method,while applied them to two fields of catalytic determination and catalytic degradation.The main content includes the following two parts.（1）Preparation of iron-carbon magnetic nanocubes（Fe/C MNCs）with enhanced peroxidase mimic activity,the material exhibits excellent peroxidase-like properties and can activate H₂O₂ to catalyze the oxidation of the substrate N,N-diethyl-p-phenylenediamine sulfate salt forms a purple product.Based on this,ultra-sensitive UV-visible spectrophotometry for H₂O₂determination was established,the value for Michaelis-Menten constant（K_m）and the maximum initial velocity(V_max)are 7.4×10^-5mol?L^-1and 4.6×10^-8mol?L^-1?s^-1,respectively.The steady-state kinetic analysis also indicates that the catalysis reaction follows a ping-pong mechanism.The absorbance（λ=550 nm）responded well linearly to H₂O₂ concentration in the range from 1.0×10^-8to 2.0×10^-4mol?L^-1,and the detection limit is 1.5×10^-9mol?L^-1.Since glucose can react with O₂to produce H₂O₂ under the existence of glucose oxidase,the glucose oxidase can be used in conjunction with the above method to measure glucose.The linear range of glucose is from 1.0×10^-7to 5.0×10^-4mol?L^-1,and the detection limit is 1.6×10^-8mol?L^-1.The analytical method was applied to the determination of H₂O₂ in rainwater samples and the quantitative and fast determination of glucose in human serum,and satisfactory results were both obtained.The new method established possess the attractive features of high sensitivity,low cost and easy storage.（2）With methylene blue,rhodamine b and methyl orange as a template,the obtained nitrogen-doped Fe@C nanoparticles（Fe-N@C NPs）are employed as heterogeneous catalysts to activate H₂O₂ to degrade organic dye under ultrasonic irradiation.The results demonstrate that the catalyst can degrade organic dyes in synergy with ultrasonic radiation.The degradation efficiency of methylene blue,rhodamine b and methyl orange are 95%,91% and 61%,respectively.Besides,the degradation efficiency of positively charged methylene blue dye is significantly improved by introducing ultrasound.And the selectivity of the dye degradation reaction can be improved,which may be due to the charge matching between the dye and Fe-N@C MNPs.Based on free radical quenching and trapping experiments,the singlet oxygen（¹O₂）produced during the activation of H₂O₂ by Fe-N@C MNPs is the active group for catalytic degradation.We propose a non-free radical pathway to explain the degradation process of organic pollutants.Also,the catalysts show good reusability and stability.These studies provide new insights into the synthesis of functional noble-metal-free materials,and they have potential applications in catalysis and wastewater treatment.