Preparation,Characterization And Enzyme Catalytic Application Of Layered Composites

Natural enzymes are biocatalysts with high specificity and efficiency under mild conditions,which play an important role in biosensors,pharmaceuticals,environmental industries,chemical industry,food processing and analytical determinations.However,its application is limited by its complex preparation process,harsh operating conditions,high cost and poor stability.Therefore,the construction of stable and efficient simulation enzymes to overcome these limitations has attracted the attention of many researchers.In recent years,nanomaterials have attracted more and more attention because of their strong stability,flexible design,simple synthesis and low cost of preparation.In 2007,it was found that Fe₃O₄nanoparticles had peroxidase activity for the first time.Subsequently,the study of nanomaterials simulating enzymes has become one of the hot spots in recent years.In this paper,a new metal layered nanocomposite was developed as a peroxidase simulation enzyme,and the catalytic activity of the simulated enzyme was further enhanced and its application in colorimetric detection was studied.Firstly,the design and research of composite materials were carried out.Because of the large specific surface area of layered composites,more active sites could be provided to achieve better catalytic effect.Using nanoflower and molybdenum disulfide as precursors to prepare layered materials,the porous network nanosheets provide favorable conditions for the good dispersion and deposition of other nanoparticles.In order to further improve its catalytic effect,the layered materials were compounded with precious metals?Au,Ag,Pt?,so as to better improve the synergistic catalytic effect of the simulated enzyme.The prepared material was then applied to the enzyme-catalyzed system,which could rapidly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine?TMB?to produce significant color changes.Similar to natural enzymes,the catalytic activity of the designed simulated enzyme is affected by p H,temperature,amount of catalyst,concentration of TMB and concentration of hydrogen peroxide?H₂O₂?,etc.Compared with natural enzymes,the designed mimic enzymes have the advantages of simple preparation,stable properties and low price.In this paper,the layered nanocomposites were prepared and their structure,morphology and composition were studied.Finally,the composite was applied to the detection of UA in human serum and showed excellent catalytic activity.Specific research contents are as follows:1.3D layered keratin nanoflowers?keratin-NF@Ag₃PO₄?modified by Ag₃PO₄nanoparticles?NPs?were prepared based on simple self-assembly method.Keratin-Cu₃?PO₄?₂·3H₂O inorganic hybrid nanoflowers were prepared by natural sedimentation method.Then the prepared keratin-Cu₃?PO₄?₂·3H₂O nanoflowers were immersed in Ag⁺solution,and converted into Ag₃PO₄NPs modified on the surface of keratin-Cu₃?PO₄?₂·3H₂O by cation exchange of Ag⁺with Cu₃?PO₄?₂.It has been proved for the first time that it has excellent catalytic activity to TMB in the presence of H₂O₂.The outstanding catalytic activity of 3D kerinin-NF@Ag₃PO₄can be attributed to its large specific surface area and porous structure.In addition,uric acid?UA?reduced ox TMB to TMB,leading to a rapid fading of solution blue and a decrease in UV-vis absorbance at652 nm.On this basis,a quantitative detection method of UA was proposed.2.The ternary PPy@Mo S₂@Au microtube was prepared by hydrothermal method to improve its catalytic activity.Firstly,Mo O₃@PPy was prepared by using Mo O₃microrod as template,and then PPy@Mo S₂nanosheet with layered structure was prepared by simple hydrothermal reaction using Mo O₃@PPy as self-sacrifs template.Considering the reduction ability of Mo S₂,a large amount of Au NPs was deposited on the surface of PPy@Mo S₂by in-situ reduction,and finally a ternary structure of PPy@Mo S₂@Au composite was formed.We also investigated the enzymatic activity of PPy@Mo S₂@Au nanocomposites in the presence of H₂O₂on the peroxidase substrate3,3,5,5-tetramethylbenzidine?TMB?.Based on these findings,a facile and convenient colorimetric route is developed for the sensitive detection of TA with a detection limit as low as 0.87?M.