Water-Soluble Nanocrystal-Micelles: New Building Blocks for Facile Constructions of 2, 3-Dimensional Arrays

Dr. Hongyou Fan
Chemical Synthesis and Nanomaterials Department
Sandia National Laboratories, Albuquerque, New Mexico

Wednesday, April 13th, 4:00PM
     Nanocrystals (NCs) exhibit unique size-dependent optical, electronic and chemical properties. The ability to adjust properties through control of size, shape, composition, crystallinity, and structure has led to a wide range of potential applications for NCs in areas like optics, electronics, catalysis, magnetic storage, and biological labeling. Furthermore, NC assembly into 2- and 3-dimensional superlattices is of interest for development of Ďartificial solidsí with collective optical and electronic properties that can be further tuned by the NC spacing and arrangement. Despite recent advances in the synthesis and characterization of nanocrystals and nanocrystalline arrays, there remain numerous challenges that limit their practical utilization. For example, synthesis procedures generally used for metallic, semiconducting, and magnetic NCs employ organic stabilizing ligands, making the nanocrystals water insoluble. This is very problematic for biological imaging and for incorporation of nanocrystals in hydrophilic sol-gel matrices like silica or titania needed for the fabrication of robust, functional lasers.
     In this presentation, I will report our recent results and progress on the synthesis of water-soluble NC-micelles and usage of such materials as building blocks to fabricate ordered, three-dimensional, NC/metal oxide arrays. The approach of synthesizing NC-micelles is to encapsulate organic monolayer derivatized, hydrophobic NCs within the hydrophobic interior of surfactant/lipid micelles that afford water-solubility. This approach is simple, general, can be extended to synthesize water-soluble semiconductor and magnetic NCs with different shapes. Subsequent self-assembly with metal oxides leads to highly ordered NC/metal oxides arrays with face-centered cubic mesophase. Through different reaction conditions, material forms (film, powder, particle), ordering, and orientation can be controlled. Integration of NC/metal oxide arrays will be also discussed. The method opens a new pathway to the fabrication of 2, 3-D NC superlattice inside inorganic framework with tunable dielectric.

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