Preparation Of Nanoparticles In Different Shapes By Using Amphiphilic Block Copolymer As Templates

In this dissertation, we systematically investigated the self-assemblies of poly(2-vinylpyridine)-block-poly(ethyleneoxide)(P2VP-b-PEO) and polystyrene-block- poly(2-vinylpyridine) (PS-b-P2VP) amphiphilic block copolymers in dilute solutions. By selective loading gold precursors HAuCl₄ in P2VP domains, various micellar morphologies were generated. In addition, the micellar formation process of micelles and the factors affecting the micellar morphologies were investigated. On the basis of the studies, we successfully fabricated various metallized nanostructures by using the self-assembled structures as templates.Firstly, we investigated the self-assembly of amphiphilic P2VP-b-PEO block copolymers in THF. It was found that Janus micelles could be formed. The formation process was studied. Addition of HCl to the micelles solution of P2VP-b-PEO copolymers leads to the formation of vesicles. Subsequently mixing a small amount of hydrazine monohydrate with the vesicle solution can induce the dissociation and reorganization of the vesicles into Janus micelles. When HCl is replaced by HAuCl₄ precursors, composite Janus particles containing gold in P2VP blocks are obtained.Secondly, a simple, facile method for the fabrication of a gold nanowire network in large scale on the solid substrates was presented. In a selective solvent, micelles of (P2VP-b-PEO) were formed. After spin coating of the micelles solution on silicon wafers, network structures of P2VP-b-PEO aggregates were obtained. The micellar films of the block copolymers were used as templatesfor the selective loading gold precursors (HAuCl₄) in P2VP domains. The gold nanowire networks aregenerated after the removal of the block copolymer templates by an oxygen plasma treatment.Thirdly, the synthesis of gold nanoparticles (AuNPs) by UV irradiation of the PS-b-PVP/HAuCl₄ or PE-b-PVP/HAuCl₄ complexes was investigated. AuNPs with block copolymer shell structures can be easily generated by simply control of the block copolymer concentration and the loading ratio of the HAuCl₄ precursor. The dry nanoparticles can easily redisperse into water and organic solvents. The resultant gold nanoparticles are stable enough to remain suspending in buffers for a relative long time and the size of the Au nanoparticles redispersed in buffers is much affected by the pH value. The AuNPs are biologically acceptable and nontoxic, which might pave the way to many applications in biomedical engineering.Fourthly, we reported a simple scheme to fabricate metallic/inorganic hybrid nanostructures by using AuNPs with PEO-b-P2VP shell structures coupled with titania sol-gel chemistry. The shape and size of the titania nanoobject can tuned by controlling the amount of sol-gel precursor. To evaluate the photocatalytic capability of the Au-Titania core-shell nanoparticles, the decomposition of MB dye under UV irradiation (254 nm) was carried out. The architectures show greatly enhanced photocatalytic activity, which is better than that of TiO₂ or Au-TiO₂ composite nanoparticles prepared under the same conditions.