Design And Fabrication Of Iron Oxide Nanocomposites And Their SERS Property

In recent years, with the increasing development of nanoscience and nanotechnology, various iron oxide nanomaterials have been fabricated and then applied in science research due to their unique properties. Among them, the magnetic iron oxide nanomaterials attracted considerable researchers’attentions because of their great potential applications in drug delivery, cancer treatment, magnetic fluids and chemical sensor. Since the discovery of surface-enhanced Raman scattering (SERS) in the 1970s, it has aroused intense interest due to its high sensitivity and specificity in analytes detection. The enormous SERS enhancement effect and simple testing condition have enabled SERS technology to be widely used in surface science, biology, medicine pharmacy, environmental monitoring, national security and other fields. The combination of magnetic iron oxide nanomaterials and noble metals can endow the final product dual functions of both magnetic response and local surface plasmon resonance. We can disperse these composites into the analyte solution to achieve the adsorption of analyte molecules. By using an external magnetic field, these composites can be separated from the solution rapidly and then for the further SERS measurement. In this paper, we first tried to fabricate iron oxide nanomaterials with different shapes, then the as-obtained magnetic composites were coated with the noble metal nanomaterials and the SERS properties of the final composites were investigated. The main contents are as following:(1) Uniform and well-dispersed spindle-like β-FeOOH nanoparticles were synthesized with simple reagents through a facile hydrothermal reaction and then characterized by various means. The effects of reaction temperature and CTAB amount on the products morphology were also investigated. Besides, in order to get the desired spindle-like Fe3O4 nanoparticles, the as-prepared β-FeOOH nanoparticles were placed in tube furnace and experienced a calcining process. However, we found that the final calcined products could not maintain the spindle morphology according to their SEM images. In order to address this problem, silica layer was introduced onto the surface of β-FeOOH nanoparticles, after that the monodispersed spindle-like Fe3O4@SiO2 nanoparticles were obtained by calcining β-FeOOH@SiO2 nanoparticles in hydrogen atmosphere and then characterized.(2) Monodispersed cubic α-Fe2O2 nanoparticles were first fabricated by a simple hydrothermal reaction. After that a modified Stober method was applied to coat silica layer onto the surface of α-Fe2O3 nanoparticles. And then the uniform and well-dispersed cube-like Fe3O4@SiO2 core-shell structures were obtained by calcining the as-prepared α-Fe2O3@SiO2 samples in hydrogen atmosphere. By using PVP as reducer, silver nanoparticles were introduced onto the Fe3O4@SiO2 surface through a one-pot hydrothermal reaction. The above obtained samples were characterized by XRD, TEM, SEM and FTIR. Besides, we also investigated the influence of the reaction time on the coverage rate of Ag nanoparticles on the Fe3O4@SiO2@Ag (FSA) surface. Finally, the magnetic and SERS properties of these magnetic composites were studied and discussed. The results showed that the FSA nanocomposites could exhibit good magnetic response and superior SERS sensitivity. The as-prepared FSA nanocomposites could adsorbed analyte molecules in solution and then easily separated with the help of external magnetic field, all of which make the FSA nanocomposites a perfect choice for practical SERS detection applications.