Fabrication Of Magnetic Metal-organic Frameworks Based Composite And Its Application In Nanozyme-SERS Catalytic Monitoring System

Surface-enhanced Raman scattering?SERS?is a fast analytical technology,which can enlarge Raman signals of the molecules absorbed on the SERS-active substrates to achieve an ultrasensitive detection.Moreover,owing to the highly specific fingerprint-like spectrum of the molecular vibrational modes,the SERS technique has been widely used in chemistry,biology,environment,medicine and many other fields.Fabrication of multifunctional nanocomposites with SERS activity is always an important direction of SERS study,providing a wider possibility for its applications.Metal-organic frameworks?MOFs?are a kind of inorganic-organic porous materials constructed from metal ions or metal clusters with bridging organic ligands via coordination bonds,which have been widely applicable in adsorption,catalysis,molecular recognition and other fields because of their specific structural feature.In this paper,we have constructed a magnetic metal-organic framework-based composite as SERS substrate.Owing to its unique structural property,it has been applied in the catalytic degradation and SERS monitoring of cationic dyes,meanwhile,its peroxidase-like activity has been further studied.The main research content is as follows:a)Fabrication ofmagnetic MOFs based composite and its application in catalytic degradation and ultrasensitive SERS monitoring of cationic dyesEnvironmental pollution is one of the top three global crises and the degradation an monitoring of pollution are always an important issue concerned by people.Due to their excellent dyeing property,cationic dyes have been widely used in dyeing of textiles.However,due to the great water solubility of cationic dyes,wastewater discharged from textile factory contains a certain amount of toxic cationic dyes.Thus,it is of great importance to study the degradation and monitoring technology of cationic dyes.In this work,a kind of magnetic MOFs based composite Fe₃O₄@Au@MIL-100?Fe?has been constructed via a solvothermal reaction,Au seed-induced growth process,and subsequent low-temperature cycling self-assembly technique.Owing to the particular MOFs shell,cationic dyes can be selectively absorbed by Fe₃O₄@Au@MIL-100?Fe?composite,meanwhile,the composite can also be used as a SERS substrate to ultrasensitive detect the cationic dyes absorbed into the MOF channel due to the SERS activity endowed by internal gold particles.Moreover,the composite can catalytic degrade the absorbed cationic dyes and its Fe₃O₄ core has offered well magnetic separation capacity,which makes the separation of materials quicker and easier.This work provided a new idea for the design of multifunctional composite SERS substrate and their application in pollution detection and disposal.b)SERS monitoring of enzyme-like reaction by magnetic MOFs based nanozymes and their photoinduced enhanced catalytic oxidation effectPreparation of multifunctional nanocatalysts with SERS activity is of significantly importance for in situ monitoring catalytic courses and studying the reaction mechanisms.In this work,peroxidase-like activity and unique photoinduced enhanced catalytic oxidation effect of the magnetic MOFs based composite have been deeply studied.The MOFs based composite not only exhibited outstanding peroxidase-like activity,but also could be used as a SERS substrate,which has been applied for in situ SERS monitoring catalytic oxidation of 3,3',5,5'-tetramethylbenzidine?TMB?in the presence of H₂O₂.Furthermore,based on the intrinsic characteristic of the Fe-based MOFs,we have discovered a photoinduced catalytic oxidation phenomenon,with the existence of light and ascorbic acid,catalytic oxidation ability of the composite can be enhanced.In addition,we have studied the photoinduced enhanced catalytic oxidation effect and proposed corresponding reaction mechanism,which have provided a theoretical support for the potential application of photoinduced enhanced catalytic oxidation effect in chemical catalysis,biological medicine and environmental manipulation.