Preparation Of Janus Nanoparticles By Using Amphiphilic Block Copolymer As Templates

In this thesis, we prepared several kinds of asymmetric nanoparticles, especially metal-metallic oxide Janus nanoparticles, by using the self-assembled structures of block copolymers and inorganic components as templates. The self-assemblies of poly(2-vinylpyridine)-block-poly(ethyleneoxide) (P2VP-b-PEO), polystyrene-block-poly (ethylene oxide) (PS-b-PEO), polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) and HAuCl₄, TiO₂, FeCl₃ were investigated. The morphological and dimensional changes of compound micelles constituted of block copolymers and inorganic components were also studied when compound micelles were treated with UV-light and alkaline liquor. Besides, we prepared asymmetric nanoparticles or arrays and studied the formation mechanisms and photocatalytic activity of asymmetric Janus particles.(1) We present a simple approach to prepare hollow particles containing a titania outer shell and an inner Au core using Au nanoparticles (AuNPs) with block copolymer shell structures as templates and combining with the sol–gel process. To this end, PVP-b-PEO block copolymer was chosen in this work. HAuCl₄ and the pyridine units can form complexes, which can induce micellar formation. The micelles consist of a soluble PEO corona and an insoluble PVP/HAuCl₄ core. During the UV irradiation process, AuNPs with block copolymer shell structures form in situ. Then the PEO blocks on the surfaces of AuNPs are exploited as anchoring sites for the growth of titania, leading to the formation of a core–shell composite nanoparticle. After removal of the block copolymers, a hollow architecture that contains an inner AuNP is generated. The architectures are expected to prevent the aggregation of the AuNPs and show greatly enhanced photocatalytic activity.(2) We suggest a simple approach towards the fabrication of an array of Janus nanoparticles consisting of noble metal and metal oxide. This approach involves the preparation of monolayer organic-inorganic hybrid films by spin coating the mixture of PS-b-PEO/HAuCl₄ solution and titania sol-gel precursor solution. HAuCl₄ and titania are incorporated in the PEO domains. Specifically, by controlling the way of removing the organic matrix, an array of Au-TiO₂ Janus nanoparticles on the substrate surface is obtained. It is found that the photocatalytic activity of the Au-TiO₂ Janus nanoparticles is enhanced as compared to that of TiO₂ or Au-TiO₂ composite nanoparticles.(3) We present a simple one-step approach to fabricate organic-inorganic Janus particles on nanometer scale. Symmetrical PS-b-PVP/FeCl₃ micelles in toluene were first prepared, and then mixed with a small amount of NaOH solution, which change the solution pH and react with FeCl₃. These processes can convert the complex micelles into asymmetric nanostructures consisting of PS-b-PVP and iron oxide. These unique substances not only preserve the variety and superiority of nanoscale properties but also exhibit great potential for definable manipulations and anisotropic performance.