Synthesis, Characterization And Properties Of Core-Shell Structured Nanoparticles

The core-shell structured nanomaterial as a kind of functional composite possessespotential applications in the field of catalysis, lithium batteries, sensors, controlleddrug delivery and targeting, and disease diagnosis and therapy. This thesis focusedmost attention on the synthesis of several core-shell structured nanomaterials, theexploration of their formation mechanism and properties, and developed a generalpreparation approach to core-shell structured nanomaterials.The uniform spherical Au@C particles with a good dispersibilty were obtainedfrom aqueous glucose solution by hydrothermal method in the presence of Aunanoparticles as seeds, and their diameters can be precisely tailored by adjusting thereaction time, temperature and other parameters. Thess size-controllable Au@Cparticles might provide excellent templates for the synthesis of heterostructuredgold-based metal oxide materials.By using Au@C particles as templates for ions adsorption and subsequentannealing treatment, Au@ZnO core-shell structure was synthesized. Furthermore, thecore-shell strucuture could be transformed to yolk-shell structure through reducing theconcentration of zinc ions, and increasing the template particle size. The UV-visabsorption spectra confirmed that the Au@ZnO nanoparticles with these twostructures both showed good absorption properties at visible light region. Using thesame method, the Au@SnO₂and Au@Fe₂O₃nanoparticles with core-shell andyolk-shell structures achieved, suggesting a novel general preparation strategy tocore-shell and yolk-shell structured nanomaterials.Through the template-based hydrothermal etching synthesis, a novel kind ofyolk-shell structured Fe₃O₄@C@F-TiO₂microspheres with fluorinated-anatasesurfaces has been prepared. In the presence of HF, the crystallization of TiO₂withsurface fluorination was significantly improved, and plenty of≡Ti-F groups wereformed on TiO₂surface leading to the increased adsorption of the dye molecules andthe reduction of photogenerated carrier recombination rate, which are favor toimproving the photocatalytic performance. Meanwhile, the existence of carbonmid-layer is crucial for the formation and growth of TiO₂and can significantly reducethe recombination rate of photogenerated carrier due to its good conductivity, thusimproving the photocatalytic activity. The presence of Fe₃O₄cores endows this material excellent magnetic separability. Due to the efficient molecular transportationand absorption, and the both carbon modification and surface fluorination improvedphotocatalytic degradation process, the magnetic Fe₃O₄@C@F-TiO₂catalysts show amore powerful visible-light driven photocatalytic activity and stability.Via a solution-based strategy, the Au@Cu₂O core-shell nanoparticles were preparedusing gold nanoparticles as seeds. Because of the smaller solubility product constantKspof copper sulfide than Cu₂O, the Au@Cu₇S₄core-shell nanoparticles wereobtained template by Au@Cu₂O. TEM results confirmed Cu₇S₄has goodcrystallization. The optical performance of this material not only displays the surfaceplasmon resonance absorption of Au nanoparticles, and also shows an enhancedabsorption with the increase of wavelength at near-infrared region ascribing to thelocalized surface plasmon resonance effect of Cu₇S₄.