Nanostructure Synthesis at the Liquid-Substrate Interface: A New Strategy for Obtaining Plasmonic and Chemically Active Surfaces

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Non-technical AbstractThe key enablers for transformative nanotechnologies are breakthroughs in both the synthesis of nanomaterials and an understanding of the chemistry and physics which guides their formation. Applications typically require that the nanomaterials be suspended in liquids or immobilized on planar substrates such as glass or silicon. While substrate-based nanostructure synthesis techniques have undeniably given rise to an impressive list of technologically relevant nanomaterials, the scope and scale of this success is dwarfed by the many accomplishments of liquid-based syntheses. With financial support from both the Solid State and Materials Chemistry program and the Electronic and Photonic Materials program in the Division of Materials Research, the research project aims to remedy this disparity through a new synthetic strategy reliant on forming nanostructures on substrates while immersed in a liquid medium. If proven successful, the approach will allow the solution-based chemistry which has proved so successful to be practiced directly on substrates and, in doing so, establish the science needed to support applications in sensing, photovoltaics and catalysis. Research activities are being integrated with undergraduate education through the supervision of summer undergraduate research internships. Outreach initiatives are being directed toward the matriculation of women into the Engineering profession.Technical AbstractThis research project seeks to determine whether synthetic protocols reliant on seed-mediated colloidal chemistry are adaptable to a substrate-based platform reliant on substrate-immobilized templates. The overriding goal is to define the chemical controls and mechanistic framework needed to form organized surfaces of noble metal nanostructures and then establish their technological relevance by demonstrating the functionalities of the plasmonic and chemically active surfaces formed. Three thrust areas advancing additive, subtractive and multistage template-assisted growth modes, which are reliant on heterogeneous nucleation and/or galvanic replacement processes, are being used to isolate the exact roles played by the substrate, reaction kinetics, pH, template material and template surface modifications in determining the reaction product. Being targeted are synthetic protocols able to define periodic arrays of: (i) core-shell structures with advanced functionalities derived from the integration of materials with dissimilar physical and chemical properties into a single nanostructure architecture, (ii) caged nanostructures offering intense plasmonic near-fields and tunable spacings between the nanostructure and its cage and (iii) substrate-based nanoframes written into patterns with predetermined layouts. These synthetic trials, combined with simulations and the use of characterization techniques which are unique to the substrate-based platform, are providing the means to form intricate nanostructures whose shape and composition are engineered to realize a desired response.