The Stability and Oxidation Resistance of Iron- and Cobalt-Based Magnetic Nanoparticle Fluids Fabricated by Inert-Gas Co
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AA5.44.1
The Stability and Oxidation Resistance of Iron- and Cobalt-Based Magnetic Nanoparticle Fluids Fabricated by Inert-Gas Condensation
Nguyen H. Hai1, Raymond Lemoine1, Shaina Remboldt1, Michelle A. Strand2, Steve Wignall3, Jeffrey E. Shield4, and Diandra Leslie-Pelecky1 1 Department of Physics & Astronomy and Center for Materials Research & Analysis, University of Nebraska – Lincoln, Lincoln NE 68588-0111, U.S.A. 2 Southeast Community College- Milford, Milford, NE 68405, U.S.A. 3 Seward High School, Seward NE, 68434 U.S.A. 4 Department of Mechanical Engineering and Center for Materials Research & Analysis, University of Nebraska – Lincoln, Lincoln NE 68588-0656, U.S.A.
ABSTRACT Magnetic nanoparticle fluids have numerous biomedical applications, including magnetic imaging, drug delivery, and hyperthermia treatment for cancer. Ideal magnetic nanoparticle fluids have well-separated, biocompatible nanoparticles with a small size distribution that form a stable colloid. We have combined inert-gas condensation, which produces nanoparticles with low polydispersity, with deposition directly into a surfactant-laden fluid to prevent agglomeration. Iron, cobalt, and iron-nitride nanoparticle fluids fabricated using inert-gas condensation have with mean particle sizes from 5-50 nm and remain stable over long periods of time. Iron and cobalt nanoparticles oxidize on exposure to air, with oxidation rates dependent on surfactant type and concentration. Iron-nitride fluids are more oxidation and corrosion resistant, while retaining the same high degree of colloidal stability. Magnetic properties vary depending on the nanoparticle size and material, but can be varied from superparamagnetic to ferromagnetic with coercivities on the order of 1000 Oe. In addition to future biomedical applications, inertgas condensation into fluids offers the opportunity to study interparticle interactions over a broad range of intrinsic materials parameters and interparticle separations. INTRODUCTION Magnetic nanoparticle fluids have a wide variety of biomedical applications, including magnetic imaging, sorting, targeting, and hyperthermia [1-3]. The majority of fluids currently used are iron oxides due to their high degree of biocompatibility; however, applications requiring magnetic targeting (such as drug delivery) would benefit greatly from nanoparticle fluids with higher magnetic moments than available from iron oxides. Chemical synthesis and mechanical grinding are common fabrication methods; however, some chemical reactions limit the materials that can be made, and many are restricted to small particle sizes. Mechanical grinding, while able to produce large amounts of material, has the disadvantage of producing large particle-size distributions. Physical-vapor-deposition methods such as inert-gas condensation offer fine control over particle-size distribution, mean particle size, and can form nanoparticles from a variety of different types of materials.
AA5.44.2
SAMPLE PREPARATION Inert-gas condensation is a process in which an atomi
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