The Fabrication Of Dielectric/Metal Core/Shell Nanoparticle Arrays And The Study Of Their Surface Plasmon Resonance Properties

Benefiting from increasing advances in nanotechnology, surface plasmons (SP) in metallic nanostructures have currently become one of the most active research topics in the field of physics, chemistry, materials science, information science, biology, and their interdisciplines. Studies on SP are now growing into a new science, named plasmonics.In this thesis, we first study experimentally and theoretically a variety of LSP modes and interparticle near-field coupling of LSP modes in monolayer metallic nanoshells which will produce a series of individual or collective optical properties. We also investigate the surface plasmon properties of the Ag nanoparticle coated with ultrathin ta-C film, and show the ultrathin ta-C film coated Ag nanoparticles application in TiO2photocatalysis. The thesis is mainly composed of three sections that are arranged as following:1. Using a double templating method by electroless deposition within a templated organic porous mold, we fabricated a monolayer of hexagonal-close-packed metallic nanoshells, each with a small opening. Light transmission spectra of the metallic nanoshell arrays are measured, which show transmission resonances at specific wavelengths whose positions are observed to be independent of the incident angle as well as light polarizations. More interestingly, the resonance wavelengths of Mie plasmon modes are also independent of the surrounding medium.Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of highly localized dipolar, quadrupolar and hexapolar Mie plasmon modes which are highly confined within metallic nanoshells.2. We studied theoretically and experimentally the appearance and properties of multiple Fano resonances in monolayer HNCP metallic shell arrays. Calculating the field intensity and field vector distributions allowed us to determine the nature of the multipolar plasmon modes taking part in the Fano interferences.In arrays of symmetric metallic shells, void plasmon modes supported by the inner surface of the individual shell act as a narrow discrete resonance, while the collective sphere-like plasmon modes formed from the near-field interaction between the individual sphere plasmons provide a broad super-radiant continuum. We demonstrated that void and sphere-like plasmons of different angular momentum could directly interact without the need of symmetry-breaking in the structure when symmetric metallic shells were patterned into ordered arrays.A cost-effective colloidal crystal templating method has been utilized to prepare the arrays of the metallic shells with small openings. The effect of the symmetry breaking on the Fano resonances were also investigated. We showed that the additional rim plasmons supported on the metallic cups could induce a dipolar charge separation across the rim of the metallic cup, which could further interact with the sphere-like and void plasmons. The Fano resonances in the metallic cup arrays are the results of the interactions between localized sphere-like, void and rim plasmons. Further tunability on the Fano resonances in metallic shell arrays is gained by changing the size of the inner dielectric core, hence changing the moment of the void-like plasmon modes and consequently the resonance frequency. Our study will be helpful to understand and exploit the complex and interesting plasmonic properties of thin metallic shell arrays. By adopting the polymer dielectric core with gain materials, such as lead sulfide quantum dots, we hope the present metallic shell arrays could find applications in near-infrared nanolasing.3. We have proposed and experimentally confirmed that incorporating an ultrathin ta-C dielectric film coated metal nanostructures with strong SP resonance into the TiO2photocatalysts can improve TiO2photocatalysis. Covering the surface of the silver nanoparticles with different thickness of the DLC thin film, and then deposited TiO2films, we found that when the thickness of the deposited DLC is10A, the decomposition rate of MB on the Ag/(10A) ta-C/TiO2photocatalyst was almost ten times and three times faster than that on TiO2alone and Ag/TiO2, respectively. With a simple dipolar-approximation, we theoretically predicted that by covering the outer surface of the metallic nanoparticles with an ultrathin dielectric film, although surface plasmon position of the metallic nanoparticles shows certain redshift, the electric field outside the nanoparticles can be further improved; For spherical metal nanoparticles, the dipolar-approximation theory predicts that the optimum thickness of the coated DLC (refractive index=2.7) is d-0.8nm. This is consistent with our experimental observations. Our proposed dense ultrathin ta-C film can also prevent the transfer of photogenerated electrons from the conduction band of TiO2to the metallic surface.