Solvothermal Synthesis And Properties Characterization Of Noble Metal And Metal Oxide Nanomaterails

The noble metal and transition metal oxide nanomaterials have been gained widespread attention for their potential application in many areas, such as catalysis, data storage, biomedicine and biotechnology. The effects of the size, structure and composite of the nanomaterials on their properties have been the research hotspots. This dissertation focused on the preparation and characterization of Pd, Fe3O4and Au-Fe3O4nanocomposites, including the controlled synthesis, formation mechanism and property characterization. It mainly contains three parts, that is, solvothermal synthesis of different nanostructured palladium nanomaterials, monodispersed magnetite nanorods and Au-Fe3O4nanocomposites, while the corresponding properties were characterized. Based upon the above studies, the relationship between nanostructures and properties of the as-prepared nanomaterials was discussed.1. Solvothermal Preparation of Pd Nanostructures under Nitrogen and Air Atmospheres and Electrocatalytic Activities for the Oxidation of MethanolIn the reaction system, PdCl2acted as Pd precursor and hexadecylamine played the roles of solvent, reductant and surface capping agent. Monodispersed Pd nanoparticles and their porous sphere-like aggregates were solvothermally prepared under different atmospheres. Different reaction atmospheres resulted in the formation of palladium with different morphologies, microstructures and different lattice parameters although they owned the same face-centered cubic structure. Oxygen existing in air resulted in the change of surface capping agent during the solvothermal reaction, which then induced the aggregation of Pd nanoparticles, and the incorporation of oxygen led to the expansion of its lattice parameter (a) to0.398nm while the standard lattice parameter in metallic Pd is0.389nm. The monodispersed nanoparticles presented better catalytic activity and stability for the oxidation of methanol than the sphere-like Pd aggregates. 2. Solvothermal Synthesis of Tunable Electroactive Magnetite Nanorods by Controlling the Side ReactionA solvothermal process was designed to synthesize magnetite (Fe3O4) nanorods using iron pentacarbonyl (Fe(CO)5), oleic acid and hexadecylamine as raw materials. In the preparation process, Fe(CO)5was firstly decomposed to form iron which were oxidized to FeO. Meanwhile, Fe(CO)5reacted with oleic acid to form iron oleate. In the system water derived from the reaction between oleic acid and hexadecylamine resulted in the hydrolysis of iron oleate to form the initial Fe3O4nanorods. In the following process, the dissolution of FeO and decomposition of residual Fe(CO)5as well as the hydrolysis of iron oleate provided the source for the growth of Fe3O4nanorods, which led to the enlargement of the particles with time. hi the reaction process, the water derived from the side reaction was the key factor to the formation of the nanorods. By adjusting the reaction time or the amount of the added hexadecylamine, the length of uniform nanorods could be tuned from63nm to140nm. Furthermore, the as-prepared Fe3O4nanorods showed excellent performance in electrochemical property and exhibited some difference from spherical nanoparticles and nanoplates in magnetic property for their shape anisotropy.3. Preparation of Fe3O4-Au Nanocomposites with Enhanced Peroxidase-like ActivityThe sphere-like Fe3O4aggregates were solvothermally prepared with ethylene glycol, sodium acetate and FeCl3·6H2O as raw materials. Fe3O4sphere-like aggregates provided the heterogeneous growth sites for the Au nanoparticles obtained by reduction of HAuCl4by sodium citrate in a mild reaction condition. As to the composites, Fe3O4sphere-like aggregates with size of200-240nm were aggregated by21.3±0.7nm nanocrystals and the Au nanoparticles were homogenously decorated on the surface of the sphere-like aggregates. In addition, the peroxidase-like activity of Fe3O4-Au nanocomposites was studied with H2O2and3,3',5,5'-tetramethylbenzidine as substrates. The Fe3O4-Au nanocomposites exhibited better catalytic activity and stability than pure Fe3O4aggregates, which might be reasoned that the interaction between gold nanoparticles and Fe3O4aggregates endows the nanocomposites made them combine with substrates easily, and the agglomeration of the gold nanoparticles could be effectively prevented, for they were located on the surface of sphere-like Fe3O4aggregates.