Sun, Dazhi (2009-05). Colloidal Manipulation of Nanostructures: Stable Dispersion and Self-assembly. Doctoral Dissertation. Thesis uri icon

abstract

  • This dissertation work addresses two important aspects of nanotechnology - stable dispersion and self-assembly of colloidal nanostructures. Three distinctly different types of nano-scaled materials have been studied: 0-dimensional ZnO quantum dots (QDs), 1-dimensional carbon nanotubes (CNTs), and 2-dimensional alpha-zirconium phosphate (ZrP) nanoplatelets. Specifically, highly crystalline ZrP layered compounds with differences in diameters have been synthesized and fully exfoliated into monolayer platelets with uniform thickness, followed by their self-assembly into liquid crystalline structures, i.e., nematic and smectic. A novel colloidal approach to debundle and disperse CNTs has been developed by utilizing nanoplatelets to gather and concentrate sonication energy onto nanotube bundles. In such a fashion, CNTs are fully exfoliated into individual tubes through physical means to preserve their exceptional physical properties. Moreover, monodisperse ZnO QDs with high purity have been synthesized through a simple colloidal approach. Exfoliated ZrP nanoplatelets are used to tune the dispersion of ligand-free ZnO QDs from micron-sized aggregates to an individual QD level depending on the ratio between nanoplatelets and QDs. Dynamic analysis suggests that the dispersion mechanism mainly involves the change of QD dispersion free energy due to the presence of nanoplatelets, so that QDs can interact favorably with the surrounding media. In addition, the nanoplatelet-assisted dispersion approach has been utilized to disperse QDs and CNTs into polymeric matrices. Dispersion - property relationship in polymer nanocomposites has been systematically investigated with emphasis on optical properties for QDs and mechanical properties for CNTs.
  • This dissertation work addresses two important aspects of nanotechnology -
    stable dispersion and self-assembly of colloidal nanostructures. Three distinctly
    different types of nano-scaled materials have been studied: 0-dimensional ZnO quantum
    dots (QDs), 1-dimensional carbon nanotubes (CNTs), and 2-dimensional alpha-zirconium
    phosphate (ZrP) nanoplatelets. Specifically, highly crystalline ZrP layered compounds
    with differences in diameters have been synthesized and fully exfoliated into monolayer
    platelets with uniform thickness, followed by their self-assembly into liquid crystalline
    structures, i.e., nematic and smectic. A novel colloidal approach to debundle and
    disperse CNTs has been developed by utilizing nanoplatelets to gather and concentrate
    sonication energy onto nanotube bundles. In such a fashion, CNTs are fully exfoliated
    into individual tubes through physical means to preserve their exceptional physical
    properties. Moreover, monodisperse ZnO QDs with high purity have been synthesized
    through a simple colloidal approach. Exfoliated ZrP nanoplatelets are used to tune the
    dispersion of ligand-free ZnO QDs from micron-sized aggregates to an individual QD level depending on the ratio between nanoplatelets and QDs. Dynamic analysis suggests
    that the dispersion mechanism mainly involves the change of QD dispersion free energy
    due to the presence of nanoplatelets, so that QDs can interact favorably with the
    surrounding media. In addition, the nanoplatelet-assisted dispersion approach has been
    utilized to disperse QDs and CNTs into polymeric matrices. Dispersion - property
    relationship in polymer nanocomposites has been systematically investigated with
    emphasis on optical properties for QDs and mechanical properties for CNTs.

publication date

  • May 2009