Preparation And Application Of Ag Ordered Nanohole Array

Surface plasmons(SPs) are collective oscillations of free electrons in noble metals that are resonantly excited by light. It can bridge the far-field light and the near-field together because it can confine light in sub-wavelength region and allows controlling of light beyond the diffraction limit. As a result of excitation, the SPs creates not only largely enhanced local electromagnetic field on the metal surface but also creates a series of other novel photovoltaic properties, which have important potential applications in many fields. Amongst diverse micro/nanostructures, ordered plasmonic micro/nanostructures posses not only optical properties for single, isolated micro/nanostructures, but also may create new collective optical properties caused by the coupling of their micro/nanostructure units. Moreover, ordered micro/nanostructures can create highly reproducible optical signals because of their ordered nature, which can be conveniently tuned by changing their structural parameters. Therefore, ordered metal micro/nanostructure arrays show great potential as a new generation optical-electronic micro/nanostructure devices. This thesis focuses on the fabrication of ordered through-void arrays and their related applications in prism-free plasmonic sensing and SERS. The main research contents and results achieved are outlined as follows:(1) Monodispersed 200-700 nm polystyrene(PS) spheres were prepared using emulsion polymerization method, and the major factors(monomer amount, stirring speed etc.) that influence the synthesis of high quality PS spheres are investigated.(2) One-tier Ag through-void arrays were prepared using nanosphere lithography combined with electroless deposition of Ag, and their EOT-based plasmonic sensing and SERS performances were investigated. Experimental and theoretical(finite-difference time-domain, FDTD) results reveal that the Ag through-void arrays create extraordinary optical transmission(EOT), which can be finely tuned by altering the arrays’ periodicity and height. The EOT property enables plasmonic sensing to be realized: the through-void arrays supported on a glass slide demonstrate a sensitivity of about 295.38 nm/RIU(RIU = refractive index unit), which can be further influenced by the arrays’ periodicity. Moreover, the same Ag through-void array can also be used as SERS substrate because of the giant localized field generated by SPs.Typical SERS enhancement factor achieved is about 104, which is reasonablyconsistent with the theoretically predicted enhancement factor, with spectral variation across the array is less than 8.08%.(3) Two-tier Ag through-void arrays were prepared using bilayer colloidal crystal template of PS spheres, and their EOT-based plasmonic sensing and SERS performance were investigated. This thesis also examined the refractive index sensing performance for the one- and two-tier arrays with different periods. Conclusively, the larger the period is, the higher the sensitivity is, and moreover, the two-tier through-void arrays show much improved refractive index sensitivity than the one-tier through-void arrays. Amongst, the two-tier Ag through-void array with period of 616 nm shows largely improved sensitivity and figure of merit(FOM), which reaches559.71 nm/RIU(RIU=refractive index unit) and 14.28 RIU-1, respectively. Moreover,the two-tier Ag through-void Arrays also demonstrate significantly improved SERS activity than the one-tier through-void Arrays when they are used as SERS substrates.