Preparation And Application Of Au-SiO₂-Au Sandwich Structure And Au Through-Void Array

Surface-enhanced Raman scattering?SERS? is a powerful surface analysis method, which can provide structural and much of other information for species adsorbed at metal surface. However, whether SERS can or not develop into an important analytical technique for practical applications mainly depends on the reproducibility and sensitivity of SERS substrate s. In SERS, nanogaps between neighboring particles or sharp projections on their surfaces can produce a very strong local electromagnetic field, known as active "hot spots". Because SERS signal is mainly contributed by molecules located in "hot spots", and thus to improve the spectral reproducibility and sensitivity, we need precisely control the number of “hot spots” and their distribution on a SERS substrate. Presently, although some methods have been developed for the construction of "hot spots", their complexity and cost largely limit their wide applications. Therefore, preparation of SERS substrates with high reproducibility and sensitivity still face a great challenge. Additionally, since Ebbesen and his colleagues found extraordinary optical transmission?EOT? in 1998, this unique optical phenomena has attractive intensive interest because of its great potential applications in plasmonic sensing. Currently, preparation of miniaturized and high sensitive plasmonic sensor is one of the hot topics in plasmon research. Thus, this thesis uses low-cost nanospheres lithography technique to prep are ordered plasmonic micro/nano structures, and by modifying its own structures, controls the number of “hot spots” and their distribution. Additionally, this thesis also use nanosphere lithography to built Au through-void ordered micro/nano structures, which enable realization of EOT-based plasmonic sensing and SERS detection on a single chip. The main research contents and results achieved are outlined as below:?1? 413?620 nm monodispersed polystyrene?PS? spheres were successfully synthesized using emulsion polymerization method.?2? Particle-dressed, silica shell-isolated cavity architectures?Au SSV/SiO₂/Au NPs? were prepared by integrating conventional techniques?e.g., nanosphere lithography etc.?. In brief, Au sphere segment void?Au SSV? array was prepared by electrodeposition of Au through the monolayer template of 620 nm PS spheres onto a Au substrate, followed by removal of the PS spheres by dissolving. Then, the Au SSV array was modified with a thin SiO₂ layer using sol-gel technology, followed by self-assembly of a sub-monolayer of 16, 30 nm gold nanoparticles on the SiO₂ surface, achieving the final particle-dressed, silica shell-isolated cavity architectures. Experimental and simulated results show that plasmonic coupling between particles and underneath Au cavities create a vast of "hot spots", thereby largely improving spectral reproducibility and sensitivity for the architecture.?3? One- and two-tier Au through-void ordered micro/nano architectures were constructed, which enable EOT-based plasmonic sensing and SERS detection to be realized on a single chip. The two kinds of through-void architecture were prepared by electrodeposition of Au through the one and two monolayer template of PS spheres?413 or 620 nm in diameter? onto ITO slides, followed by removal of the PS spheres. This thesis examined their EOT properties and EOT-based plasmonic sensing performance, and reveal that the two-tier Au through-void array show much improved sensitivity for refractive index sensing than the one-tier Au through-void array, and meanwhile the two-tier Au through-void array show SERS activity.