Research And Development Of Magnetic Nano-silica

As a new functional material,the study of magnetic composite particles has developed quickly in recent years.It's applications in immunoassay lead to a new idea for bio-separation and detection.The development of magnetic particles with functional unites was described in this paper,and displayed it's application in cell separation,fixation of enzyme,target presenting,protein purification,nucleic acid separation and clinical diagnosis.The aim of this thesis is to prepare Fe3O4@SiO2 composite functional particles with simple operation and high quantity.Their chemical and physical characteristics were analysed comprehensively.(1)In this paper,chemical co-precipitation method was used to prepare the magnetic particles with hydriphilicity.The Fe304@Si02 composite particles are obtained through sodium silicate of hydrolyzation,and SiO2 was produced on the surface of Fe304 particles.The composite particles are characterized by a series of techniques including TEM,XRD,FTIR and VSM.Some factors that would influence the result were discussed in particular,such as interaction temperature,time,concentration of regents,pH,and etc.The TEM images showed that the nanoparticles were favorably dispersible,but the nanoparticles were not uniform.(2)In order to improve the uniformity of composite particles,the surface of Fe3O4 was modified with oleic acid(OA),then Fe3O4@SiO2 magnetic composite particles were prepared in sodium silicate of hydrolyzation with Fe3O4/OA composite particles as previous particles,with a better uniformity than that of Fe3O4 composite particles.Because Fe3O4/OA composite particles cannot disperse in alcohol/water,we packaged the particles in sodium silicate of hydrolyzing process with toluene(toluene can be soluble in ethanol as random ratio)as co-solvent to disperse composite particles in alcohol/water.Uniformity of Fe3O4/OA composite particles was rather better,so that of the final Fe3O4@SiO2 magnetic composite particles was also better.The TEM images showed that the nanoparticles were uniform,and well dispersed with a size of about 20 nm.(3)According to the optimal reaction conditions referring to the previous test results,we took the scale-up experiments in 5L reaction still.TEM,XRD,FTIR patterns showed that Fe3O4@SiO2nanoparticles were prepared by pilot scale experiments.And the particle size was the nearly same as that prepared from the experiments in a raw laboratory scale.(4)The Fe3O4@SiO2 nanoparticles were functionized with KH-560.The Fe3O4@SiO2 nanoparticles were bonded to BSA through an amide bond.Therefore,the covalent binding between Fe3O4@SiO2 and protein molecules was realized to achieve the goal of protein separation.The results showed that the mass of bovine serum albumin bonded to 1.0 mg magnetic nanoparticles was 17.12ug.We also used the Fe3O4@SiO2 nanoparticles in the selective adsorption experiment for separating the flavonoids.It turned out that Fe3O4@SiO2 could adsorb flavonoids obviously,implying its optimistic prospect.It is believed that the preparation technique of magnetic nano-silica using cheap raw materials with simple operation and high yield,should contribute to the manufacturing of well dispersed magnetic nano-silica with low cost,resulting in promotion of the magnetic nano-silica industry.