Abstracts Category : Other

Structural Engineering of Optical Nanomaterials

by Yaocai Bai

Optical nanomaterials have attracted tremendous interest from a large community of researchers because of their widespread applications. The optical properties are closely related the structures of nanomaterials, thus making the structural engineering over nanomaterials in a controlled manner an important topic. This dissertation discusses our efforts in the engineering and applications of optical nanomaterials including noble metal nanostructures and hollow nanostructures.Noble metal nanostructures possess novel optical properties due to localized surface plasmon resonances. Controllable synthesis of noble metal nanostructures with desired morphology and optical properties is highly desirable. In this work, we attempt to prepare anisotropic Ag/Au alloy nanorods with homogenous compositions through a high-temperature annealing process. Alloy nanorods exhibit strong surface plasmon resonances with high stability upon etching. Tunable and fascinating optical properties are achieved through controlling over aspect ratios and compositions of the nanorods.Improved understandings on the properties of resorcinol-formaldehyde (RF) resins will benefit the colloidal synthesis of RF-based nanomaterials. In this study, the chemical stability and the evolution of both surface properties and chemical structures of RF resin spheres are systematically studied, which provide guidance for the rational design and fabrication of various hollow nanostructures. Based on the new understandings, an extension of the surface-protected etching strategy has been adopted for the preparation and engineering of hollow RF nanostructures. A RF-template-engaged redox reaction method is proposed and utilized for rational synthesis of mesoporous hollow manganese oxide nanostructures. Visible resonant Mie scattering properties are theoretically simulated and experimentally demonstrated.Finally, a couple of novel optical demonstrations based on the design and structural engineering of nanostructures are presented. The first one is the design of plasmonic dichroic film on a mirrored substrate, which has been realized by spray-coating core-shell nanostructures. By structural engineering over the core-shell particles, dichroic film with multi-colors has been successfully created, which holds great potential in anti-counterfeiting. The other one is related to the modulation of light transmittance and the drying process of hollow nanostructures. Au nanoparticles are incorporated into the hollow structures and employed to probe the drying process.