Physicochemical characterization of Fe_3O_4/SiO_2/Au multilayer nanostructure

摘要

The purpose of this research was to synthesize and characterize gold-coated Fe_3O_4/SiO_2 nanoshells for biomedical applications. Magnetite nanoparticles (NPs) were prepared using co-precipitation method. Smaller particles were synthesized by decreasing the NaOH concentration, which in our case this corresponded to 35 nm using 0.9M of NaOH at 750rpm with a specific surface area of 41 m~2g~(-1). For uncoated Fe_3O_4 NPs, the results showed an octahedral geometry with saturation magnetization range of 80-100 emu g~(-1) and coercivity of 80-120 Oe for particles between 35 and 96 nm, respectively. The magnetic NPs were modified with a thin layer of silica using Stober method. Small gold colloids (1-3 nm) were synthesized using Duff method and covered the amino functionalized particle surface. Magnetic and optical properties of gold nanoshells were assessed using Brunauer-Emmett-Teller (BET), vibrating sample magnetometer (VSM), UV-Vis spectrophotometer, atomic and magnetic force microscope (AFM, MFM), and transmission electron microscope (TEM). Based on the X-ray diffraction (XRD) results, three main peaks of Au(111), (200) and (220) were identified. The formation of each layer of a nanoshell is also demonstrated by Fourier transform infrared (FTIR) results. The Fe_3O_4/SiO_2/Au nanostructures, with 85 nm as particle size, exhibited an absorption peak at ～550 nm with a magnetization value of 1.3 emu g~(-1) with a specific surface area of 71 m~2g~(-1).