Synthesis And Property Studies Of Magnetic Hybrid Nanoparticles

Magnetic nanoparticles are of great interest for researchers from a wide range of disciplines, including magnetic fluids, catalysis, biomedicine, magnetic resonance imaging, data storage, and environmental remediation. However, naked magnetic nanoparticles are chemically highly active, and are easily oxidized in air, resulting generally in loss of magnetism and dispersibility. Nano-engineering the magnetic nanoparticles and other materials into a single entity would not only improve the stability of magnetic nanoparticles, but also generate novel properties and potential applications. Such nano-assembly can lead to innovative materials which exhibit more broad application prospects. Synthesis and property studies of magnetic hybrid nanoparticles have already become the research hotspot.Magneto-opto-fluorescent FeAu@ZnO and La_1-xSr_x MnO₃@Au ZnO, and Rh doped Fe₃O₄ nanoparticles were prepared by nanoemulsion methods with the poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol）（PEO-PPO-PEO） copolymer or the polyvinylpyrrolidone（PVP） as the surfactants, environmental friendly metal complexes as the precursors. The nature performances of naoparticles were analysized by X-ray diffractometer（XRD）, transmission electron microscopy（TEM, including high-resolution TEM）, fourier transform infrared spectrometer（FT-IR）,ultraviolet-visible light absorbance spectrometry（UV-Vis）, photoluminescence spectrophotometry（PL）,vibrating sample magnetometer（VSM） and physical property measurement system（PPMS）. The nanoparticles modified by the bio-friendly molecules were provided with better water-solubility and biocompatibility. Thus the nanoparticles are expected to have more broad application prospects. The subject of the work is summarized as follows:1. Synthesis of bi-phase dispersible core-shell FeAu@Zn O magneto-opto-fluorescent nanoparticlesBi-phase dispersible core-shell FeAu@ZnO magneto-opto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using poly（ethylene glycol）-block-poly（propylene glycol）-block-poly（ethylene glycol）（PEO-PPO-PEO） as the surfactant. The morphological and structural analyses show virtually uniform, spherical in shape with the narrow particle size distribution, high crystallinity and evident core-shell configuration of Fe Au@ZnO nanoparticles. The UV-vis and PL results reveal thewell-behaved absorption bands including surface plasmon resonance and multiple visible fingerprint photoluminescent emissions of the nanoparticles dispersed in both hydrophilic and hydrophobic solvents.The nanoparticles manifest soft ferromagnetic and/or near superparamagnetic behavior with a small coercivity of ¹9 Oe at room temperature. The corresponding magnetic hysteresis curves were elucidated by the modified Langevin equation. Moreover, the processes of solvent dispersion-collection of the nanoparticles were demonstrated for application readiness of such core-shell nanostructures.2. Synthesis and characterization of La_1-xSr_xMnO₃@AuZnO magneto-fluorescent nanoparticlesThe PVP capped La_1-xSr_xMnO₃@AuZn O magneto-fluorescent nanoparticles were synthesized by a modified nanoemulsion process using polyvinylpyrrolidone（PVP） as the surfactant. The morphology and core-shell nanostructure of the resultant nanoparticles is identified by TEM/HRTEM and XRD, which show the nanoparticles having good crystallinity, virtually uniform, spherical in shape with the narrow particle size distribution, evident core-shell configuration. The comparison FT-IR study proves the PVP coating on the surface of the resultant nanoparticles. The nanoparticles exhibit well-defined optical and magnetic properties, and show superparamagnetic behavior at room temperature.3. Synthesis and properties studies of Rh Fe₃O₄ composite nanoparticlesRhFe₃O₄ composite nanoparticles were productively synthesized via a one-pot nanoemulsion process by simultaneously reducing the precurous of rhodium（II） acetate dimer and iron（Ⅲ） acetylacetonate with polymer PEO-PPO-PEO as the surfactant. The morphology and structure of the nanoparticles were analyzed by TEM and XRD. FT-IR studies were performed to found the coverage of the amphiphilic,electrically neutral, non-toxic and stable polymer on the nanoparticle surface. Magnetic measurements were performed by VSM and PPMS to evaluate the magnetic properties of the nanoparticles. It is found that the nanoparticles reveal soft ferromagnetic behavior. The RhFe₃O₄ composite nanoparticles are hopeful for being a promising catalyst.