Synthesis And Propetries Of Nanoshell Spheres Through Polymer Assisted Methods

Nowadays, the nanoshell spheres have been considered as important kinds ofmaterials in nanoscience. Depending on the structure and composition, they can bedivided into three categories, namely core-shell spheres, hollow spheres and rattle-typespheres. Compared with the simple nanospheres, the nanoshell spheres usually containtwo or more compositions, which facilitate the integration of multifunction fromdifferent materials into one single sphere. And the structrues of the nanoshell spherescan be finely designed and regulated to meet the demands of applications. As thedevelopment of nanoscience and nanotechnology, the nanoshell spheres are widely usedin various applications such as drug delivery, catalysis, energy storage, sensors and selfassembly.One impediment to the development and utilization of the nanoshell spheres istheir tedious synthesis. For example, in the conventional synthesis, the preparation ofthe core-shell spheres usually requires multi-steps, such as synthesizing the corematerial in advance, surface modification and coating the core with the shell material. Inthe case of hollow or rattle-type spheres, the synthesis is more complex, since templateremoval steps are often needed. Therefore, developing simple and effective approachfor the synthesis of nanoshell spheres is highly demanded. Based on the interactionbetween the polymer and the inorganic nanospheres or their precursor, some simple andeffective methods are established here to synthesize the nanoshell spheres using theclassical colloidal chemistry. In chapter2, we have synthesized the hollow silica spheres via a polymer assistedmethod. We choose the silica particles prepared by the sol-gel process （the well-knownSt ber method） as the starting material. Firstly, the as-prepared silica particles are gentlyetched with a NaOH solution without using template molecules to make them porous.Then, a poly-dimethyldiallylammonium chloride （PDDA） layer is introduced onto thesurface of the porous silica spheres by electrostatic interaction. Finally, the PDDAcoated porous silica spheres are further etched by ammonia solution to form the hollowsilica nanospheres. Compared with the traditional template method, in our process, thestarting material is the St ber silica particles, which is easily to prepare and nosurfactant or expensive organic silica precursors are needed. In addition, thanks to theetching treatment, large pores （>10nm） can be formed on the silica shells, which aresuitable for the entrance of the biomolecules. The adsorption results show that thehollow silica spheres can effectively uptake the biomolecules such as hemoglobin （320mg·g-1）.In chapter3, based on the coordination effect between the poly acrylic acid （PAA）and the metal ions, a PAA assisted method have been developed to fabricate manganeseoxide loaded hollow silica particles. The synthesis involves formation of PAA-Mnaggregation particles and coating silica on the outer surface of the particles. Theas-prepared silica coated aggregation particles are subsequently calcined in air at500°Cto remove the polymer inside the particles and transform the metal salt into thecorresponding metal oxides. Compared with the conventional method, the metal oxidesare mainly trapped inside the hollow silica particles. As the formation of the hollowstructure and the metal oxide are simultaneous, so multi-steps are no longer needed. TheMn content as well as the inner structure of the particles can be easily tuned bychanging the initial dose of the Mn salt. More importantly, gas molecules such as H2O,CO₂and CO are released during the PAA decomposition, which facilitates theformation of porous structures in the products. The manganese oxide loaded hollow silica particles show excellent performance in the catalytic oxidation of dyedecomposition （MB and Rb）. Furthermore, this method can be extended to synthesizeother metal oxides （such as MgO and NiO） loaded hollow silica particles.In chapter4, a polymer assisted method has been developed to synthesizeFe₃O₄@C core-shell nanospheres. A natural polymer, Arabic gum, is selected as thecarbon source, which can be easily adsorbed onto the surface of Fe₃O₄during the onepot solventhermal synthesis. By simple annealing the Arabic gum coated Fe₃O₄nanospheres at N2atmosphere, Fe₃O₄@C core-shell nanospheres can be obtained.Compared with the frequently-used glucose carbon coating method, the formation ofFe₃O₄and the coating of carbon precursor can be achieved in one step. Moreover, thereleased gas from the decomposition of the urea during the synthesis makes the finalFe₃O₄@C core-shell nanospheres porous. The Fe₃O₄@C core-shell nanospheres areused as the anode material in Li ion battery, the results show that they exhibit very highreversible capacity, durable cycling performance and high rate capability.