Study On Optimization Of Peroxidase Activity Of ZIF-67-derived Hollow Co₃O₄ Nanocage And Its Complex

The metal-organic framework is a porous nanomaterial cross-linked by organic imidazole ester and transition metal.It has the characteristics of large specific surface area,high porosity,strong versatility,adjustable structure and function,and high stability.Enzymes are extremely important catalysts in organisms.Artificial enzymes can make up for the shortcomings of natural enzymes,such as low operational stability,easy inactivation,and difficulty in recovery and recycling.It has a wide range of applications in various fields.Metal oxides as peroxidases have been extensively studied due to their low cost,high efficiency and stability advantages.Among many metal oxides,Co₃O₄,as a peroxidase,has excellent performance in all aspects,but nano-Co₃O₄ is easy to aggregate,which will affect its catalytic activity.Using ZIF-67 as a sacrificial template,nano-cage Co₃O₄ can be obtained,which can retain its high peroxidase activity while having the advantages of ZIFs.In summary,this thesis uses ZIF-67 as the precursor to prepare Co₃O₄ hollow cage nanomaterials（Co₃O₄ HNCs）and Co₃O₄/Au hollow cage nanomaterials（Co₃O₄/Au HNCs）two functional nanomaterials.The peroxidase properties were studied and applied to the detection of dopamine and glucose respectively.This article mainly includes the following:（1）Using ZIF-67 as the precursor,Co₃O₄ HNCs were prepared by simple calcination.The particle size,porosity,specific surface area and other characteristics of the material were tested and characterized.The results show that Co₃O₄ HNCs can efficiently catalyze the oxidation of the color substrate 3,3’,5,5’-tetramethylbenzidine（TMB）by H₂O₂ to obtain the blue oxidation product（ox TMB）.The catalytic mechanism was analyzed,Co₃O₄ HNCs can catalyze the rapid decomposition of H₂O₂ into dissolved oxygen,and act as a bridge for electron transfer to quickly catalyze the oxidation of TMB.The steady-state dynamic parameters of the system were tested by the double reciprocal mapping method.In addition,the factors affecting the catalytic efficiency were optimized,and the system was successfully applied to the detection of dopamine.Compared with other systems,this system can detect dopamine in both high and low concentration ranges,and has the characteristics of low detection limit and high sensitivity.（2）On the basis of the obtained Co₃O₄ HNCs,gold nanoparticles were loaded to obtain the Co₃O₄/Au HNCs composite material.The composite materials were tested and characterized by XRD,particle size and other methods,which showed that Au was successfully compounded to the surface of Co₃O₄ HNCs.Experimental investigations showed catalytic mechanism was explored,and the enhanced peroxidase activity of the composite material originated from the synergistic effect of Co₃O₄ HNCs and Au NPs,Au NPs can catalyze H₂O₂ to generate hydroxyl radicals,and can cooperate with active oxygen to oxidize TMB,thereby enhancing the catalytic activity of the material.The steady-state kinetic parameters of the test system showed that its affinity for hydrogen peroxide was improved.Therefore,compared with Co₃O₄ HNCs alone,Co₃O₄/Au HNCs are more suitable for the sensitive detection of glucose,and have the characteristics of low detection limit,large range and high sensitivity.