Besides being of fundamental scientific interest, magnetic core-shell nanoparticles have significant application in cell targeting therapies when exposed to an oscillating magnetic field. Difficulties with growth of a continuous noble metal film on the terminating surfaces of an iron oxide nanoparticle hinder the controllable synthesis of these important materials. In this work, various syntheses have been correlated to the structure and morphology of the resulting materials through High

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... ion Transmission Electron Microscopy (HRTEM), Selected Area Diffraction (SAD), and Infrared (IR) spectroscopy. Magnetic iron oxide cores were synthesized in an aqueous oxygen-depleted environment by coprecipitation of FeCl 2 and FeCl 3 in an alkaline environment [1]. The nanoparticles were washed and suspended in .1M tetramethylammonium hydroxide, and size fractionated by centrifugation. The colloid was aged at least 3 days in an argon atmosphere before addition of 2.75E-3 % hydrazine in degassed dH 2 O. Au shells were precipitated onto the iron oxide cores by dropwise addition of tetrachloroauric acid from a 4% stock solution [2]. Coated and uncoated NPs were deposited onto carbon-coated grids and analyzed in a Hitachi H9000 HRTEM operated at 300keV, and in a probe corrected FEI Titan STEM operated at 200keV. Other particles were dried, combined with KBr, and pressed into a disc measured in a Bruker 66V IR Spectrometer.