Synthesis And Properties Study Of Rare Earth Coordination Polymer Micro-nano Materials

In recent years,researchers have devoted extensive scientific attention to the design and synthesis of rare earth coordination polymers.Among them,luminescent rare earth coordination polymers constitute an active research field.Because of the electron density interaction between the metal center and the organic ligand in the rare earth coordination polymer,the rare earth coordination polymer has unique luminescence characteristics.In addition,coordination polymers provide unique luminescence and electronic properties.Its related electronic properties can be adjusted by changing its chemical structure,the chemical structure can be controlled by adjusting the interaction between the metal and the ligand at the molecular level.Polymers are also recognized as coordination polymers or coordination networks,and most of them are multifunctional luminescent materials.In these luminescent materials,clusters are generally formed through coordination bonds,and interact through weak van der Waals forces,p-p bonding,and hydrogen bonds.This clearly shows that coordination polymers can have infinite structures,and these varying structures can be achieved by choosing different metal ions or different ligands.Coordination polymers are characterized by high surface area,permanent porosity,adjustable optical properties,strong adsorption affinity and stable magnetic properties.Coordination polymers have been used in bioimaging,gas storage,drug delivery,heterogeneous catalysis,energy conversion and chemical sensing.The luminescence of rare earth coordination polymers is usually caused by its chemical composition,that is,the characteristics of organic ligands coordinated with metal centers or metal clusters.In addition,due to the adjustable molecular structure of coordination polymers,the construction of coordination polymers has been rapidly developed.In recent years,it has been discovered through research that the high coordination number of lanthanide ions may lead to difficult-to-control synthesis reactions,making it difficult to control the structure of the product.However,the interesting geometric structure and properties of polymers have attracted the interest of more and more chemists.Based on the above content,this thesis adopts the doping of different metal ions to prepare several different coordination polymer micro/nanospheres.The main research contents of this paper are as follows:(1)Microwave synthesis of Eu₂O₃:Gd³⁺nanospheres,characterization,magnetic,optical performance research.Europium nitrate,gadolinium nitrate and urea were used as raw materials,and the europium-based polymer nanospheres were prepared by a simple microwave synthesis method.Then,it is calcined at high temperature.Finally,we analyze the products produced.The experimental results showed that the optimal reaction conditions were 90?and 60 min by the microwave hydrothermal synthesis method,change the reaction time and adjust the concentration of reactants.The europium-based polymer nanospheres were successfully prepared.Subsequently,the precursor was calcined.The morphology and fluorescence properties of the obtained product before and after calcining were compared.The fluorescence intensity after calcining was significantly different from that of the precursor.In addition,we have done some research on the biological properties and magnetic properties of polymers.(2)Study on preparation,upconversion luminescence and magnetic properties of gadolinium coordination polymer.Using gadolinium nitrate hexahydrate as the source of central ions,rare earth ytterbium and erbium as doping ions,and 2-bromoterephthalic acid as ligands,a series of Yb³⁺,Er³⁺doped Gd-based up-conversion spheres with a particle size of400-800 nm and good dispersibility were obtained by solvothermal method.After comparing experimental conditions and experimental phenomena,the appropriate conditions are as follows.The rare earth doping ratio is 60%for gadolinium ions;30%for ytterbium ions;10%for erbium ions,and the ratio of organic ligands to metal ions is 2:1,the solvent ratio of ethanol to N,N-dimethylformamide is 1:1,the reaction temperature is 160?,and the reaction time is 6 h.We compared the luminescence properties and morphological characteristics of the synthesized coordination polymers.The product was then calcined in an air atmosphere at 800?for 4 h.The results showed that the typical product was calcined in an air atmosphere at 1000?,and the luminescence performance was greatly improved after 4 h.And the magnetic properties of the product have been studied,and the product has typical paramagnetic properties.(3)Microwave synthesis of Gd₂O₃:Yb³⁺:Er³⁺nanospheres:characterization and performance studies.Using gadolinium nitrate,ytterbium nitrate,erbium nitrate,and urea were used as raw materials,a gadolinium-based polymer was successfully prepared via a simple and rapid microwave hydrothermal synthesis method.The synthesized products were characterized and measured by SEM,EDS,XRD,TG and other methods.Then the product was calcined at 800?in air for 6 h.The fluorescence properties of the products before and after calcining were compared.