Preparation Of Functional Magnetic Nanoparticles And Preliminary Application Of Heavy Metal And Pathogens Separation

Magnetic nanoparticles, which display nano-size effect, have good dispersion in solution, and show superparamagnetic property at ordinary temperature, in other words, magnetic particles perform magnetism in magnetic field environment, when withdrawal the magnetic field, particles’ magnetism disappear immediately. Under the orientation control of external magnetic field, the absorbed target can be quickly separated from the multi-component environments by cleaning and desorption operation. Consequently, magnetic nanoparticles have been found wide potential applications in food analysis, bioseparation and environmental monitoring, etc. Sample preparation would be optimized by the combination with the magnetic nanoparticles and traditional detection methods as well as the improvement of sensitivity and analysis efficiency. This article was mainly focused on the study of preparation and functional Fe3O4 magnetic nanoparticles. Furthermore, this dissertation preliminary investigated the effect of separation and enrichment common pathogens and heavy metal ions by functional magnetic nanoparticles. The main parts of the results are summarized below:1、The Fe3O4 magnetic nanoparticles were prepared by co-precipitation method. Stober method was utilized to coat Fe3O4 magnetic nanoparticles by silica layer, the product was Fe3O4@SiO2. The morphology, structural, chemical compound and magnetic characteristics of the Fe3O4 and Fe3O4@SiO2 magnetic nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), Zeta potentiometric analyzer, vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and Fourier transformed infrared spectroscopy (FT-IR). The results showed that the average partical size of Fe3O4 and Fe3O nanoparticles was 10 and 15 nm; The acid experiment showed that Fe3 nanoparticles had good acid-base resistant; Magnetic measurement revealed both of them have good magnetic response and nearly superparamagnetic with a saturation magnetization of 98.42 and 53.87 emu·g-1.2、Animation and carboxyl-functionalized Fe3O4 magnetic nanoparticles with core-shell structure were carried out with 3-aminopropyltriethoxysilane and succinic anhydride onto Fe3O4@SiO2 nanoparticles. The morphology, structural, chemical compound and magnetic characteristics of the Fe3O4@SiO2-NH2 and Fe3O4@SiO2-NH-COOH nanoparticles were characterized by TEM, XRD, EDS, VSM, TGA and FT-IR. The size of functional Fe3O4 magnetic nanoparticles was lager than Fe3O4@SiO2 nanoparticles, particle size range between 10～30 nm; the surface of functional Fe3O4 magnetic nanoparticles have been successfully modified amino and carboxyl groups. Magnetic measurement revealed both of them have good magnetic response and nearly superparamagnetic with a saturation magnetization of 48.72 and 41.84 emu·g-1, So they could satisfied the separation requirement.3-. The positive charges on the surface of Fe3O4@SiO2-NH2 nanoparticles can promote strong electrostatic interaction with negatively charged sites on the surface of bacterial pathogens to exhibit efficient adsorptive ability. Nanoparticles ensure a high binding affinity to at least eight different species of Gram-positive (B.subtilis、B.cereus、S.aureus、M.luteus)and Gram-negative (E. coli、S. Typhi、S. Sonnei、E. sakazakii) bacteria. Adsorption equilibrium was achieved rapidly in 1 min. Various factors affecting the absorption efficiency of bacterial pathogens such as solution pH, PBS buffer solution concentration and ionic strength were researched. In pH range of 3-9, the absorption efficiency had no significant change, and the adsorption efficiency of pathogenic decreased with the PBS buffer concentration and ionic strength increased, the results responsed that acting force between particles and bacteria was electrostatic adsorption.4、The adsorption properties of the Fe3O4@SiO2-NH-COOH nanoparticles for the removal of Cu2+、Pb2+and Hg2+ in aqueous solution were investigated. Various factors affecting the absorption behavior of Cu2+、Pb2+and Hg2+ such as initial pH, initial concentration of heavy metal ion and contact time were researched. The results showed that Fe3O4@SiO2-NH-COOH nanoparticles had good adsorption effect and reuse properties. Adsorption equilibrium was achieved rapidly in 10 min, adsorption data was fitted well with the Langmuir isotherm models with the maximum adsorption capacity of 43.48,34.27 and 11.65 mg·g-1, the maximum uptake of heavy metal ion was recorded at pH 7.In this study, magnetic Fe3O4 nanoparticles were prepared, which displayed superparamagnetic property, its average particle size was 10 nm. After wrapped up SiO2 protective layer on its surface, nanoparticles still had good magnetic response which could met the separation requirement, nanoparticles aslo had good acid and alkali resistance, so it could be adequated for variety of chemical enviromnents. It was easy to linking-up amino, carboxyl and hydrosulfide groups on the surface of silicon layer by chemical modification, which could improve its affinity and response characteristics for the target matter. The functionalized magnetic nanoparticles possessed favorable adsorption properties for common pathogens and heavy metal ion. Hence, the functionalized magnetic nanoparticles display extensive applications in modern analytical technology, life sciences and food safety analysis, etc.