A Research On Gold And Its Composite Nano-Structure With Semiconductor:Synthesis And Optical Properties

Because of its distinctive and excellent properties, gold nano-structures has been a hot spot of nano science and technology in recent20years. Gold can ex-cite surface plasmon resonance(SPR), and control of its shape, size and structure can tune SPR peak from500to above1000nm. Further more, gold is chemi-cal stable and biocompatible, all of which expands its vast and important usage in domains like Surface Enhanced Ramman Scattering(SERS), bio-sensoring, medical imaging and therapy and catalysis. Based on above situation, our re-search is focused on synthesis and optical properties of gold nano-structures and its composites with semiconductors, and we hope our conclusions can provide basic principles for other relevant researches.In this thesis, we systhesis gold nanorods(GNRs), Au-core-Ag-shell(Au@Ag) nanoparticles, Au-Ag-alloy(AuAg) hollow nanoshells, Au-Ag-alloy(AuAg) nan-otubes and Au-semiconductor nanotubes by liquid phase reduction method. We then characterize the shape and lattice structure of as-prepared samples by Scan-ning Electron Microscope(SEM) and Transmission Electron Microscope(TEM), and obtain the optical spectrum by UV-vis Absorption Spectrophotometer and electromagnetic simulation softwares. We also use self-building Z-scan system to measure the nonlinear optical coefficients.We synthesis single-crystalline gold nanorods by seed-mediated methods and control the aspect ratios by vary the addition of silver nitrate. Our research reveals that silver nitrate plays a vital role in anistropic growth of GNRs, and less than a specific amount, increasing the amount of silver leads to the in-creasement of aspect ratio; however, above the amount, increasing the amount of silver leads to the decreasement of aspect ratio. We explain the phenomenon by CTAB bi-layer template and underpotential deposition of silver. Besides silver nitrate, CTAB and HAuCl4also affect GNR growth. We also research nonlinear optical properties of GNRs, and finds that when irradiated by laser with spcific intensity and wavelength, the nonlinear absorption coefficients of GNR is relevant to aspect ratio. The reason is that nonlinear optical property is apart from local electric field enhancement induced from SPR.We synthesis Au-core-Ag-shell(Au@Ag) nanoparticles by depositing sil-ver onto gold nanoparticles, and by reacting it with HAuCl4, we get Au-Ag-alloy-hollow incomplete nanoshells. By UV-vis absorption test, we find that with the etching of Au@Ag, the absorption peaks red-shifts; by electromag-netic simulation with ddscat, we find that red-shift is originated from the for-mation of shell and increase of Au proportion. By Z-scan measurement, we find that the formation of Au-Ag-alloy shell increases the nonlinear optical ab-sortion coefficients and further corrosion of the Au@Ag nanoparticle increases both nonlinear refractive and absorption coefficients.We use silver nanowire as sacrificing template and reduce it with HAuCl4and obtain Au-Ag-alloy(AuAg) nanotubes based on the Galvanic Replacement method. We characterize their shape, lattice structures and chemical elements by SEM and TEM and confirm the existance of AuAg alloys. We then research UV-vis absorption spectrums of AuAg nanotubes and find that as corrosion pro-ceeds, two absoiption peaks emerges and red-shifts. By simulation, we ascribe this phenomenon to the decreasement of tube thickness and increasement of Au proportion. By electromagnetic simulation of COMSOL(?), we research SPP propagation properties of AuAg nanotubes and find that there is non-significant lose of energy with specific incident wavelength and tube thickness. With the method of cation exchange, we finally syntheis AuAg-CdS nanotubes and re-search their shape and crystalline structures by SEM.