Preparation Of Platinum And Palladium-coated Iron Oxide Nanocomposites

At present, considerable effort has been devoted to tailor the surface properties of the nanoparticles in order to meet their application requirement, especially in catalyst field by using magnetic separation. As important iron oxides of nanomaterials, both maghemite and magnetite nanoparticles have lots of promising applications due to their properties. Considering the above reasons, our research focused on the preparation of platinum (Pt) and palladium (Pd)-coated iron oxides-based nanocomposites and the thesis consists of the following contents:Section 1 summarized magnetic nanoparticles'preparation; their surface functionalization and their latest advances for catalyst application.Section 2 reported the maghemite nanopowders preparation and related surface modification, and we investigated its properties and structure. We employed silane to obtain surface-tailored amino-coated and thiolated maghemite NPs, and compared corresponding properties and structure. Major results were detailed as follows:1. Maghemite nanopowders of ca. 16 nm were prepared by thermal method; corresponding properties and structure were studied;2. Silane bridged surface tailoring of maghemite was employed to obtain amino-coated and thiolated magnetite nanoparticles (NPs) via corresponding 3-aminopropyltriethyloxysilane (APTES) and mercaptopropyltriethoxysilane (MPTES) modification, respectively. The results prove that the surface functionalized magnetic particles have slight dimensional increase in average diameter.Section 3 described a new approach to prepare two noble mental functionalized magnetic nanoparticles (Fe₃O₄/Pt ,γ-Fe₂O₃/Pt andγ-Fe₂O₃/Pd) by sonochemical synthesis. Meanwhile, their structure and magnetic properties were investigated. The three nanoparticles were characterized and proven some results as follows:1) Fe₃O₄/Pt magnetic nanoparticles were prepared by direct and indirect approach. Its morphology is sphere and it displays well dispersion of diameter ca. 91 nm, moreover, the crystal structure of Fe₃O₄/Pt magnetic nanoparticles was totally accordant with that of Pt nanoparticles.2) Theγ-Fe₂O₃/Pt magnetic nanoparticles were successfully synthesized by direct approach, and the microstructure is spherical with a diameter of ca. 68nm. The crystal structure ofγ-Fe₂O₃/Pt magnetic nanoparticles was totally accordant with that of Pt nanoparticles.3) Theγ-Fe₂O₃/Pd magnetic nanoparticles were successfully synthesized by indirect approach. The microstructure is spherical but its diameter is ca.17 nm which is smaller than that of Pt composites. The crystal structure ofγ-Fe₂O₃/Pd magnetic nanoparticles was totally accordant with that of Pd nanoparticles. Section 4 described a new approach to prepare Pt and Pd mental nanoparticles by sonochemical synthesis. The sonochemical method is a time-saving and effective alternative. As-prepared Pt and Pd nanoparticles through sonolysis demonstrated a good dispersion, and their morphology was uniform with crystal structure. The diameter of Pt and Pd nanoparticles is ca.80 nm and 8 nm, respectively. However, the dispersion of Pt nanoparticles is better than that of Pd nanoparticles.