The Preparation And Optical Properties Of Metal Micro-nano Structure

Nowadays, noble metal micro-nano material is a hotspot in the field of nano-optics because of their special optical properties presented when the metal nano-structures interact with electromagnetic waves. They may have great potential applications in the surface enhanced Raman scattering spectroscopy, chemical and biological sensors, solar cells and nonlinear optics. At present, many researchers have carried out their works on the mechanism between the electromagnetic wave and the metal nano-structures, such as single metal nanoparticle, disordered metal nanoparticles and metal array nanostructure. They provided the experimental and theoretical basis for the further study. In this thesis, we focused on the fabrication and the optical properties of the spacing-controlled metal nano-structures and the asymmetrical metal nano-shell.On the fabrication of metal nano-structure, nano-sphere lithography is a simple, cheap and fast approach. But colloidal spheres always appear non uniform in the process of self-assembly because of the coffee-ring effect. To avoid this problem, we developed a new method called "the mixed solution gas-liquid-solid interface self-assemble". During the process of self-assembly, colloidal spheres formed the monolayer array structure under the action of capillary force, molecular force and electrostatic force. By using this monolayer template, we fabricated several kinds of metal nano-structures and studied their optical properties.The first part is the preparation and optical properties of metal nanoparticle array structure with the controllable spacing. We fabricated the monolayer colloidal spheres with controllable spacing by oxygen plasma etching and analyzed the relationship between etching time and spacing. The metal core-shell structure, nano-triangle and nano-hole array structure with controllable spacing were fabricated by the monolayer colloidal spheres. Then we analyzed the transmission and absorption spectra of these nanostructures. We detected Raman spectrum of single molecular R6G by metal nano-triangle structure. When the resonance wavelength of metallic nano structure is consistent with the excitation wavelength of Raman spectrum, the enhancement factor can be up to106.The second part is focused on the research of asymmetric metal nano spherical shell array structure. In our experiment, we found some new interesting phenomenon that the symmetry of Au@PS (polystyrene) was broken, when Au@PS reacted with dichloromethane solution. We prepared the asymmetric metal nano-shell with different opening size and direction by controlling the Au@PS etching time, and then we analyzed the optical properties of asymmetric metal nano-shell in different polarization. These structures may have potential applications in negative refractive index materials.In the third part, we prepared silver nano-cones, hexagonal gold nanoparticles array structure and three dimensional nano-hole structures. The silver nano-cones were fabricated by the second deposition of silver on the Au triangle arrays. The hexagonal gold nanoparticles array structures were prepared by annealing method in different temperature. The three dimensional nano-hole structures were fabricated by double-layered colloidal spheres. These various metal nanostructures will provide useful experimental materials for the researches and the applications of nano-optics.Outlook:Colloidal spheres lithergraphy as an effective, low cost and simple way can prepare the various metal nano-structure. The metal nano-structures will play more and more important role in the surface enhanced Raman scattering spectroscopy, biological sensors, energy materials, negative refractive index materials and nonlinear optics because of their special optical properties.