Preparation Of Magnetic Fluorescent Bifunctional Nanoparticles By Coupling Method And Their Application

In this work,the preparation of quantum dots,the preparation of magnetic nanoparticles by self-assembly method,and the synthesis,characterization and preparation mechanism of magnetic fluorescent nanocomposites were studied.The effects of p H and organic ligands on the preparation of quantum dots were investigated.And the effect of p H on the preparation of aminated magnetic nanoparticles was also studied.Finally,quantum dots and magnetic nanomaterials were combined through chemical bonds to obtain composite nanoparticles with fluorescence and magnetic properties.First,in this experiment,cadmium-based quantum dots were prepared using the water phase method.The results show that the p H value affects the growth rate and emission wavelength of CdTe quantum dots.Generally,as the p H increases,the growth rate increases.The surface ligand also affects the growth rate,particle size distribution,and stability of quantum dots.Quantum dots modified by MAA(Mercapto acetic acid)have fast growth rates and a wide and unstable particle size distribution.Relatively speaking,quantum dots modified by MPA(3-Mercaptopropionic acid)have better stability.In addition,we also studied the preparation of Cd Se quantum dots,and found that the preparation of Cd Se has higher requirements on temperature.Secondly,based on past research,this experiment further studies the effect of p H on the preparation of aminated magnetic nanoparticles by self-assembly method,and builds a theoretical model.It was found that the p H value does affect the self-assembly effect of 4-vinylaniline and constitute different self-assembly systems.At p H = 3.2,a single-layer monomer coating can be constructed,while at p H = 4.5 or above,a double-layer or multi-layer coating is formed.Thirdly,in this experiment,magnetic fluorescent composite nanoparticles were successfully prepared by chemically bonding carboxyl groups on the surface of quantum dots and amino groups on the surface of magnetic nanoparticles.However,experiments have found that the composite nanoparticles have a poor stability but unstable in p H buffer solutions.It is stable only in a mixed solution of NaOH / HCl or deionized water.However,it still showed good magnetic and fluorescent properties.Finally,we applied composite nanoparticles to immobilize bovine trypsin.It was found that the carboxyl group activity on the surface of the composite nanoparticles was high,and the adsorption capacity of the enzyme reached 280 mg/g.