| The physical and chemical properties of noble metallic nanostructures are very dependent on their size, shape and composition, which also endow them the potential that impulses the development of nano-scale technology, including catalysis, medicine and optics. Especially, due to the novel and unique properties result from the decline of symmetry, anisotropic nanocrystals increasingly draw people’s attention. Among them, the Ag triangular nanoplate (Ag TNP) is considered as one of the most remarkable materials, and the optic properties, anisotropic energy and abundant methods of synthesis controlling aspect ratio make them broad-spectrum. Meanwhile, the outstanding performance in optics and relatively low cost are also factors that people try best to study it. However, the relatively active chemical property and the instability of the triangular plate like configuration are problems which hard to solve and use. Recently, researches have shown that multi-component nanostructures, including core-shell and alloy, effectively expand the application of single-component nanocrystals. Combination of multiple elements would not only compensate their defects, but also enhance or even engender their properties. Thus, study the growth mechanisms and properties of Ag TNP-based multi-component nanomaterials is of great significance.This thesis relates to silica coating, Au NR embedding and Au alloying Ag TNPs, and investigation of their synthesis and optical properties. The detailed studies should be summed up as follows:1. Synthesis of regular Ag TNP by reducing of NaBH4in solution. Under the condition of containing protective agent (MUA) and ample silica precursor (TEOS), investigating the thickness-different coating resulting from the different types and concentration of base catalyst (ammonia or hydrazine hydrate). The TEM images show that controlling the catalyst, coating and aging time can manipulate the shape of silica shell without obtaining cross-link one. UV-Vis spectra show that the silica shell coating does not affect the optical properties of the silver core, and their location of SPR peaks remain unchanged.2. Au nanoring@Ag core-shell nanostructures with controllable morphologies and tunable symmetries are synthesized via seed-mediated growth of Ag onto the sole seed:cirular Au nanorings (Au NRs). The2D isotropic Au NR is firstly prepared by chemical etching, and galvanic replacement with HAuCl4. With delicately altering the regrowth procedure and mixing capping agents, different Ag triangular nanoplates with embedded Au NRs in different sizes and shapes can be obtained. Furthermore, by using exclusive capping agents, the growth of Ag on Au NR can be preferentially confined in a lateral or vertical mode to form eccentric nanoplate or nanocube in both sequence sets at room temperature. Such nanostructures with precisely controllable shape evolution displayed unique optical properties, and revealed the feasibility of breaking the original dimension and especially symmetry at nanoscale by seed-mediated growth, which paves the way for future applications including catalysis, diagnosis, plasmonics, biological and chemical sensing.3. Ag triangular nanoplates (Ag TNPs) precursor transform to Ag/Au triangular nanoframes (Ag/Au TNFs) were obtained by one-step facile galvanic reaction. TEM images show that the reaction firstly occurred at the edge and then the face of Ag TNP, and the UV-Vis spectra show the SPR slowly and regularly red-shift, which can be used as a facile SPR-controllable material. The Ag/Au alloy TNFs with well-tuned LSPR exhibited high stability under the near-infrared laser and tough ion-contained environments, and can be used for two-photon luminescence. The1ppm-HAuCl4Ag/Au TNP shows the best stability, without any change after illumination. The two photon emission spectra show the relationship with SPR, and with a large TPA cross section calculated as6.34X104GM, the Ag/Au TNFs showed considerable TPL performance with referential Au nanorods (Au NRs). |
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