| Nanocomposite materials, composed of more than one kind of nanoscale functionality, are a relatively new class of materials, which are constructed on a nanometer length scale by the incorporation of several components with different properties. Nanocomposite materials with unique properties can be designed and fabricated to cater for various particular needs by combining several pure materials. Nanocomposite materials have received considerable attention in both fundamental and applied research due to their special properties in optics, calorifics, electrics, magnetics, mechanics, and so on. Now, nanocomposite materials have become an important branch of research in high-tech materials fields.Bifunctional magnetic-optical FeAu alloy and core-shell Fe3O4 /Au nanoparticles were prepared by the one-pot nanoemulsion or modified polyol process with gold acetate and Fe(III) acetylacetonate as the precursors with different surfactants. The characterization of nanoparticles was performed using UV-Vis spectroscopy(UV-Vis), Fourier transform infrared spectrometer(FTIR), X-ray diffraction(XRD), transmission electron microscopy(TEM) and vibrating sample magnetometry(VSM). The size, shape, size distribution, structure, magnetic and optical and other chemistryphysical properties of the nano-materials were studied. The main results are summarized as follows.1. FeAu monodisperse nanoparticles were prepared by the one-pot nanoemulsion process with oleic acid and oleylamine as the surfactant and cosurfactant. The TEM and XRD analyses confirm the formation of the nanostructure with the average diameter ~5.6 nm. The UV-Vis analyses show that the SPR absorption peak of FeAu nanoparticles red-shift and broaden comparing with Au nanoparticles with similar diameter.2. PVP coated AuFe nanoparticles were prepared by a one-pot nanoemulsion process. The characterization proves the integration of the optical functionality of Au and the magnetic properties of iron. The FTIR study establishes the PVP molecules present on the surface of the nanoparticles, whereas the structural analysis verifies the formation of the alloy nanostructures of ~11.3 nm in diameter with a narrow distribution of particle sizes. The magnetic measurement shows the soft ferromagnetic behaviour of the PVP-coated nanoparticles with a small coercivity of ~40 Oe at room temperature.3. Magnetic-optical FeAu multifunctional alloy nanoparticles coated by the PEO-PPO-PEO triblock copolymer were prepared through a one-pot nanoemulsion synthesis. The size of nanoparticles were controlled by changing molar ratios of precursor and surfactant. The FTIR assessment shows the PEO-PPO-PEO molecules present on the surface of the nanoparticles, whereas the structural and morphological analysis offers the crystallographic parameters of the alloy nanostructures with a tight particle size histogram. From the magnetic measurements, the PEO-PPO-PEO coated nanoparticles show the soft ferromagnetic behaviour with small coercivity at room temperature. Subsequently, the pertinent magnetic hysteresis curves were handled by the modified bi-phase Langevin equation, which was plausibly understood as a consequence of the bimodal particle size distribution. The optical property of the nanosystem was determined by the UV-Vis measurements, revealing a broad surface plasmon absorption band located visible region.4. Polyvinylpyrrolidone(PVP)-coated monodispersed core-shell Fe3O4 /Au magnetic-optic multifunctional nanoparticles were synthesized in the presence of PVP polymer as the surfactant by using a modified nanoemulsion process. The nanoparticles were investigated by means of TEM, XRD, VSM, FTIR and UV-Vis. The formation of the core shell nanostructure was discussed. The size distribution of the nanoparticles was determined. The surface plasmon characteristic and magnetic properties of the Au nanoshell were evaluated. It was found that the titled nanoparticles had excellent magnetic susceptibility.
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