Enzyme-Like Activity Of Nanomaterials Derived From Metal-Organic Framework And Their Analytical Applications

Enzymes are closely related to life activities in nature.Natural enzymes have the characteristics of high catalytic efficiency,strong substrate specificity and mild conditions,which have been applied in various fields.However,natural enzymes also suffers from the intrinsic defects,such as inactivation,difficulty in purification,and high cost,which limits their practical application.Therefore,researches on mimic enzyme emerged.Nanozymes are a new type of mimetic enzyme.Owing to their advantages of the great characteristics of nanomaterials,easy to modify,easy to regulate the catalytic activity,nanozymes have become a hotspot in the field of mimetic enzymes.However,preparing of nanozymes with high catalytic activity is still a problem.Metal-organic frameworks are an ordered porous crystalline material.The nanomaterials derived from the metal-organic frameworks possess high specific surface area and high porosity,which reflect great application prospects in the field of nanozymes.Therefore,we choose the common metal-organic framework as a template to prepare a series of new nanoenzymes via carbonation method,evaluate their catalytic activity,establish colorimetric methods for detecting hydrogen peroxide,glucose,and dopamine（DA）.The paper is divided into the following four chapters.1.First,we briefly introduce the development of nanozymes in recent years from two parts including the type of nanozymes and their application.Then we illustrate the research significance and research background.2.Fe₃C/C nanomaterials were synthesized by directly carbonizing the Prussian blue.The Fe₃C/C nanocomposites could catalyze TMB-H₂O₂ system,which demonstrates its peroxidase-like activity.The as-prepared materials were confirmed by XRD,FT-IR and other characteristics.We have proved that Fe₃C/C materials have high stability over a wide range of pH and temperature.Steady-state kinetics experiments showed that the catalytic behavior of Fe₃C/C nanocomposites conformed to the typical Michaelis-Menten kinetic model and followed the ping-pong mechanism.In addition,Fe₃C/C showed good affinity for both TMB and H₂O₂.The free radical trapping experiment proved that the O₂·^-and·OH radicals played a key role in the catalytic process.Based on the peroxidase-like activity of Fe₃C/C,we have developed a colorimetric method for the detection of H₂O₂ and glucose.The linear range of H₂O₂was 5×10^-6mol/L to 6×10^-5mol/L with the detection limit of 4.86×10^-6mol/L.The linear range of glucose was 1×10^-55 mol/L to 6×10^-55 mol/L with the detection limit of5.95×10^-66 mol/L.Finally,Fe₃C/C-TMB-H₂O₂ system have been applied to the determination of glucose in human serum successfully.3.In this part,firstly,ZIF-8 was reacted with tannic acid and KOH to form ZIF-8surrounded by K-TA shell（ZIF@K-TA）.Secondly,cobalt nitrate was mixed with ZIF@K-TA in methanol solution,which made ion-exchange reaction occur between K⁺on the shell of K-TA and Co²⁺to form ZIF@Co-TA complex.Finally,the as-prepared ZIF@Co-TA was carbonized in a N₂ atmosphere at 800 ^o C to obtain the porous carbon/Co composite nanomaterial（Co@NHPC）.In the absence of H₂O₂,Co@NHPC can directly catalyze the oxidation of TMB,indicating that it shows oxidase-like properties.Co@NHPC also possessed high stability over a wide range of pH and temperature.Reactive oxygen species（ROS）experiments showed that the¹O₂,·OH,and O₂·^-radicals were all involved in the catalytic oxidation of TMB by Co@NHPC.Based on the inhibitory effect of DA to oxidase-like activity,we developed a colorimetric method for rapid detection of DA.The linear range of DA was 5×10^-8mol/L to 2×10^-55 mol/L,and the detection limit was 5×10^-88 mol/L.The spike method have been used to detect the DA in human serum,and the recovery rate was satisfactory.4.In this part,firstly,we used hydrothermal method to reflux copper nitrate and ZIF-67 in ethanol to form ZIF-67/Cu HD.Then the ZIF-67/Cu HD was carbonized in air atmosphere to obtain the Co₃O₄/CuO HNCs nanocomposites.The as-prepared Co₃O₄/CuO HNCs were characterized by SEM,TEM,XPS and XRD.The oxidase-like activity of Co₃O₄/CuO HNCs nanocomposites was explored,and they displayed enhanced oxidase-like activity in comparison to that of pure Co₃O₄ or CuO.The result of the reactive oxygen species（ROS）measurements indicated that¹O₂ and O₂·^-radicals were major ROS in catalytic oxidation of TMB by dissolved oxygen in the TMB-Co₃O₄/CuO HNCs system.The enhanced oxidase-like activity is probably attributed to the porous structures and synergistic effect between Co₃O₄ and CuO,which can adsorb more dissolved oxygen from solution onto its surface to generate more¹O₂and O₂·^-radicals.Based on inhibiting effect of dopamine（DA）to TMB oxidation,a simple,sensitive,visual and colorimetric method with TMB as the substrate was developed for detecting DA.This colorimetric method can be used for colorimetric detection of DA with a limit of detection of 2.67×10^-88 mol/L and a dynamic range of5×10^-88 mol/L to 8×10^-66 mol/L.We have also proved Co₃O₄/CuO HNCs are highly stable over a wide pH and temperature range.Based on the great selectivity of Co₃O₄/CuO HNCs,we have determined DA in human serum and dopamine hydrochloride injections by using the spike method.