Iron Oxide Composite Nanoparticles and Sensing Properties
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Iron Oxide Composite Nanoparticles and Sensing Properties Lingyan Wang, Xiajing Shi a), Sakienah Mahs, Jeongku Choi, Karan Sarup, Guannan Roger Wang, Jin Luo, Susan Lu a), and Chuan-Jian Zhong* Department of Chemistry, a)Department of systems science and industrial engineering, State University of New York at Binghamton, Binghamton, New York 13902, USA. * To whom correspondence should be addressed ([email protected])
ABSTRACT This paper reports findings of an investigation of the synthesis of monolayercapped iron oxide and core (iron oxide)-shell (gold) nanocomposite and their assembly towards thin films as sensing materials. Pre-synthesized and size-defined iron oxide nanoparticles were used as seeding materials for the reduction of gold precursors, which was shown to be effective for coating the iron oxide cores with gold shells (Fe oxide@Au). The unique aspect of our synthesis is the formation of Fe oxide@Au coreshell nanoparticles with controllable surface properties. By controlling the reaction temperatures and manipulating the capping agent properties and solution compositions, the size, shape, composition, and monodispersity can be tailored. The core-shell nanoparticles were shown to form molecularly-mediated thin film assemblies using molecular mediators. The sensing properties of the nanostructures on piezoelectric devices were examined for the detection of volatile organic compounds. The preliminary results have provided important insights into the design of core-shell nanocomposites as sensing materials.
INTRODUCTION Iron oxide nanoparticles have been extensively studied due to magnetic properties and superparamagnetic phenomena for exploring technological applications of the nanoscale core, shell or the core-shell combination, including magnetic resonance imaging for medical diagnosis, high-density magnetic recording, controlled drug delivery, biological targeting or separation. [1-4]. A key to these applications includes the ability to control the size, shape, composition and interparticle spatial properties when dealt at a nanoscale level. Recently, some examples of gold-coated magnetic core/shell nanoparticles are reported, which were synthesized using reverse micelle method to coat gold on iron nanoparticles [5-7] or gold (silver) on magnetite nanoparticles [8], and depositing gold onto iron oxide nanoparticles in an aqueous solution via hydroxylamine [9]. The formation of thin films of magnetic nanoparticles has also attracted considerable interest. For example, using polymer-mediated assembly method, thin films of polymerFePt nanoparticles and arrays have been deposited on Si substrates [10, 11]. Using evaporation method together with applied magnetic field parallel to the substrate (e.g., HOPG), thin film assemblies of magnetic nanoparticles have been prepared and studied [12]. While these prior studies have shown viabilities of synthesizing and assembling
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core-shell types of nanoparticles, the precise control of the continuous nature of the metal coating, th
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