Synthesis And Applications Of Unconventional Multicomponent Nanostructures

The fast development of nanoscience and nanotechnology endows nanomaterials superior performance and great potential in diverse fileds,ranging from energy to biomedicine.Multicomponent nanosctructures?MCNs?naturally integrate two or more different materials into one system with nanoscale domains.These MCNs not only inherit the intrinsic properties of each constituent component,but also exhbit intriguing new physical and chemical properties that arise from the synergetic effect of the multiple directly contacted disparate components.What's more,the spatial distribution of dissimilar components within individual MCNs is crucial in defining the properties and hence applications of these MCNs.Hense,rational desisn and synthesis MCNs with desired topology is of vital importance.The most widely exploited wet-chemical strategy for synthesizing MCNs is the so-called‘seeded-growth'method in which a secondary inorganic material is selectively deposited onto the surface of a primary seed nanoparticle?NP?.The growth mode of a secondary material and the structure of resulting MCNs can be largely deduced from the equilibrium consideration of interface energy arising from lattice mismatch between the two materials.Alternatively,kinetic control can also be employed to promote the anisotropic deposition.However,both thermaldynamic and kinetic control have their intrinsic drawbacks that limit the high-oder control in rational design and synthesis sophisticated MCNs.Thus,the thesis focus on developing innovative approaches to synthesize MCNs with pre-disigned size,shape and topology.The thesis first describes a polymer-assisted seeded-growth strategy for the synthesis a gallery of coaxial-like and Saturn-like MCNs.Polymers locally collapsed on the surface of Au nanorods or nanospheres form immobilized rigid blocks and serve as effective protection layer on the Au NP seed to guide the selective deposition and growth of a secondary material on the unprotected surfaces.Secondly,a simultaneous alloying-etching strategy is developed for the synthesis of Pt nanotubes or nanorings by selective etching Au core from coaxial or Saturn-like Au/Pt MCNs.Both the inner diameter and thickness of the nanotubes could be precisely controlled.The superior catalytic performance of the nanotubes with ultrathin side walls are further demonstrated in electrochemical oxygen reduction reaction.Finally,the thesis introduces a direct cold welding process between as-synthesized single-component Au and Ag₂S nanoparticles in solution,which subsequently leads to the formation of Au-Ag₂S MCNs.The diffusion of Au into Ag₂S domains is observed in the derived hybrid oligomers and is believed to originate the welding process.The welding process is also largely dependent on the desorption of surface ligands that brings NPs into close proximity through Van de Waals interaction.When anisotropy Au nanorods and nanowires are used,the cold welding can take place at particular surface of the anisotropic Au nanoparticles,leading to the formation of more complexed MCNs.