AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Aerosol Synthesis of Superparamagnetic Silica-Coated Iron Oxide Nanoparticles
PINGYAN LEI, Steven Girshick, University of Minnesota
Abstract Number: 95 Working Group: Synthesis of Functional Materials using Flames, Plasmas and other Aerosol Methods
Abstract Superparamagnetic iron oxide nanoparticles (SPIONs) are currently of interest for biomedical applications, including as contrast agents for magnetic resonance imaging and as targeted agents that can be heated by applying an alternating magnetic field, killing cancer cells by hyperthermia. We here report the synthesis of SPIONs that are coated with thin layers of silica. Silica coatings improve the nanoparticles’ stability, suppress agglomeration, and can serve as an excellent substrate for additional surface layers or biofunctionalization. The SPIONs were synthesized by injecting ferrocene vapor and oxygen into an argon/helium DC thermal plasma. Size distributions of particles in the reactor exhaust were measured online using an aerosol extraction probe interfaced to a scanning mobility particle sizer, and particles were collected on transmission electron microscopy (TEM) grids and glass fiber filters for off-line characterization. The morphology, chemical and phase composition of the nanoparticles were characterized using TEM and X-ray diffraction, and the magnetic properties of the particles were analyzed with a vibrating sample magnetometer and a magnetic property measurement system. Aerosol at the reactor exhaust consisted of both single nanocrystals and small agglomerates, with a modal mobility diameter of 8-9 nm. Powder synthesized with optimum oxygen flow rate consisted primarily of magnetite (Fe3O4), and had a room-temperature saturation magnetization of approximately 40 emu/g, with a coercivity and remanence of 26 Oe and 1.5 emu/g, respectively. After exiting the plasma reactor the SPIONs are coated with very thin layers of silica, using photochemical vapor deposition, driven by a xenon excimer lamp that emits at 172 nm. Tetraethylorthosilicate (TEOS) vapor was used as the coating precursor. Results are presented for the effect of operating parameters on coating thickness, surface chemical composition, magnetic properties, and stability of the nanoparticles in aqueous dispersion.