Fabrication, Properties And Applications Of Magnetic Hybrid Nanoparticles

Magnetic iron oxide and their hybrid nanoparticles have been used for magnetic separation in chemical and biological fields. The surface-enhanced Raman spectroscopy (SERS) integrated high sensitivity with rich structural information and thus had tremendous potential application for chemical and biological sensing. By the combination on the magnetic properties of the core nanoparticles and high sensitivity of SERS contributed by the Au shell, the magnetic separation on the chemical and biological molecules were achieved and SERS was developed as a powerful tool for on-line monitoring the separation procedure and evaluating the separation efficiency. Therefore, fabrication of magnetic composites with optimal saturation magnetization and high SERS activities enable us to extend its application in chemical and biological fields. Based on the above fact, the research was focused on the following issues:(1) Magnetic Fe2O3 @ Au, Fe2O3 @ Au @ Ag, Fe3O4 @ Au core @ shell nanoparticles have been prepared. The optical properties could be tuned in a wide range by adjusting the molar ratios of Au and Ag in order to optimize SERS effect. The results revealed the bimetallic shells have much higher SERS activities than monometallic shell, which is attributed to the coupling effect of Au and Ag shells and pinhole effect on the surface of nanoparticles. To further improve the efficiency of magnetic separation and SERS activities of metallic shells, we prepared a series of Fe3O4 nanoparticles with different sizes and also developed spherical, flower-like and spikes-like Fe3O4 @ Au core @ shell nanoparticles. The results revealed that the flower-like nanoparticles exhibited the highest SERS effect.(2) Fe3O4, Fe3O4 @ SiO2 and Fe3O4 @ C core @ shell nanoparticles have been prepared for separation of target antigens and surface enhanced Raman immunoassay analysis(SERIA). The results showed Fe3O4, Fe3O4 @ SiO2 and Fe3O4 @ C nanoparticles have much higher efficiency than Fe2O3@Au nanoparticles. Moreover, Fe3O4@C core@shell nanoparticles have the following advantages:(a) Carbon materials improve biocompatibility and stability of magnetic nanoparticles in aqueous solution because of the hydrophilic groups on the carbon surface. (b) The functional groups (-CHO,-COOH) bonded to the carbon frameworks make biomolecules readily graftable on the carbon surface for further biomedical application.(3) The high cost and difficulty in the recycling of noble metal nanocatalysts limited its application. Fe3O4 supported metal (Au or Pt) nanoparticles were prepared as highly efficient and recyclable catalysts for the reduction of 4-nitrophenol in the presence of NaBH4. The catalytic activities of the oxide supported metal catalysts have been largely enhanced, which is attributed to the synergetic effect that occurred at the interface of metals and oxide support. By comparing the changes in the catalytic activities of Fe3O4 @ SiO2 and Fe3O4 @ C supported Pt nanoparticles, one can assume that the enhanced activities were originated from the charge transfer between the Fe3O4 core and attached metal nanoparticles.