Synthesis Of Enzymatic Porous Inorganic-Organic Composites And Its Colorimetric Sensing Study

With the rapid development of economic globalization and the continuous acceleration of urbanization,the rapid and accurate analysis methods have become an urgent need for many fields.Enzyme is an important biological catalyst.The advantages of enzyme catalysis include the specificity of the substrate,the high efficiency of the reaction,and the mildness of the reaction conditions,which are in line with the development trend of the green chemistry industry upgrade and have shown high application value and potential in the field of analysis.However,biological enzymes have obvious disadvantages,including poor enzyme stability and difficulty in recycling（soluble in water）.Biological enzyme immobilization technology can overcome the above shortcomings.The materials currently used for enzyme immobilization can be roughly divided into three categories:inorganic carriers,polymer carriers and composite carriers.Porous inorganic-organic composite materials have large specific surface area,high porosity,tunable framework structure and good chemical and thermal stability.Therefore,its applications in heterogeneous catalysis,gas separation and storage,host-guest assembly,and high-efficiency immobilization have made considerable progress,and have good application prospects in related fields such as medical,energy and environment.This thesis is mainly focus on the needs of environmental analysis based on enzymes.The porous inorganic-organic composite material is synthesized in one step by enzymatic-induced synthesis method,with simple preparation steps and mild reaction conditions.A series of enzyme-based porous inorganic-organic composite materials were successfully prepared and successfully applied to the quantitative analysis of some typical analytes.This subject provides new ideas for the design and preparation of functional inorganic-organic porous materials,and provides a certain theoretical basis for the development of new analysis methods.The main work of the thesis is as follows:1.The multi-enzyme composite inorganic nanomaterials composed of alcohol oxidase,peroxidase and calcium phosphate were prepared by enzymatic one-step co-precipitation method for quantitative analysis of alcohol.The linear regression equation is Y=0.08974X+0.06762,（where X represents the concentration of alcohol,Y represents the absorbance）.This bio-inorganic nanocomposite has a layered porous structure and a large specific surface area,can load more enzymes,increase the contact area of the enzyme-catalyzed reaction and reduce the spatial distance of the substrate required for each enzyme-catalyzed reaction.Enzyme activity and stability are significantly enhanced,thereby shortening the time for detecting alcohol and improving detection sensitivity.2.The porous hydrogel composite material coated with double enzymes（glucose oxidase and peroxidase）was prepared by enzymatic one-step polymerization method for glucose detection.Glucose oxidase and peroxidase are embedded in the hydrogel together,and glucose is decomposed to generate hydrogen peroxide under the action of glucose oxidase.Under the catalysis of peroxidase,hydrogen peroxide is reduced while oxidizing3,3’,5,5’-tetramethylbenzidine for color development,realizing the naked-eye detection of glucose at a level of 10μM.The calibration curve equation is Y=0.3232 log X-0.0658,（where X represents the glucose concentration and Y represents the absorbance）,and the LOD of this method is as low as 1.6 m M.The hydrogel system effectively improves the efficiency of the multi-enzyme cascade reaction,maintains the enzyme activity of the multi-enzymes,ensures the reliability of the result and can be used for direct colorimetric detection of glucose in complex systems such as serum.In addition,based on this method,a low-cost,easy-to-operate and easy-to-storage analysis kit has been delicately prepared,which can be used for home medical care.Compared with the blood glucose meter,the detection system is low in cost and easy to industrialize.3.ZIF-8 material is prepared by enzymatic one-step mineralization method using biological mineralization strategy,while choline oxidase,cholinesterase and peroxidase are embedded in ZIF-8 to improve enzyme stability and obtain porous inorganic-organic composite materials.For the first time,the stable MOF material（ZIF-8）was synthesized in the water phase by electrochemical method.Then the multi-enzyme mineralized MOF composite material is prepared in one step by electrochemical method,and was characterized.Furthermore,a sensitive biosensing platform based on this material is constructed for the quantitative detection of organophosphorus pesticide,which realizes the colorimetric detection of organophosphorus pesticide.The calibration curve equation is Y=0.6655-8.5125*10^-4X+2.5503*10^-7X²（R²=0.9998）,（where X represents the concentration of profenofos and Y represents the absorbance）.The MOF material has a large surface area to provide more active sites,which provides a guarantee for more enzyme loading.The enzyme can be adsorbed in the pores of the MOF,which helps to maintain the stability of the enzyme.