Date of Award

2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Chemistry

First Advisor

Thomas Mallouk

Abstract

The design of materials with tunable properties is at the forefront of material-based applications. The key to materials design is understanding their fundamental characteristics and establishing a structure-property correlation. This dissertation explores fundamental aspects of synthesis and characterization of functional materials designed using colloidal crystals, inverse replicas, and layered materials for electronics and energy devices applications. We have combined particle assembly and High Pressure confined Chemical Vapor Deposition (HPcCVD) to create ordered and electrically continuous 3D nanostructures of metals and semiconductors, defined as metalattices. These nanostructures have crystalline arrays of uniform particles in which the period of the crystal is close to the characteristic physical length scale of the material, for example, exciton Bohr radius in semiconductors, making them tunable for electronic, plasmonic, thermoelectric and spintronics applications. Silica nanoparticles in the range of 20-120 nm, assembled as micron thick films using vertical deposition technique, were used as templates for metalattice design. The interstices in the colloidal crystal films were infiltrated with polycrystalline semiconductors (Ge/Si/ZnSe) and metals (Ni/Pt/Ag/Pd/Au) using HPcCVD to obtain corresponding metalattices.We have developed a core-shell chemical passivation strategy for Ge metalattice prepared by infiltration of ~70 nm silica colloidal crystal using HPCVD. The oxide-free Ge core shows quantum confinement which depends on the void size in the silica template. The size of Ge sites dictated by the voids in the template and core-shell interdiffusion of Si and Ge can, in principle, be tuned to modify the electronic properties of the Ge metalattice. We have also investigated the structures of colloidal crystalline films and germanium metalattice in detail by scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS). Particles smaller than ~32 nm diameter assemble into body centered cubic, whereas particles larger than 32 nm assemble into random hexagonal close pack structures with 2D hexatic phase. Polycrystalline films of these materials retain their structure, and long-range order upon infiltration at high temperature and pressure, and the structure is preserved in Ge metalattice. This detailed understanding of particle arrangements in the template can help in establishing structure-property relationships in the metalattices. We also explore material design made from layered materials for application in energy systems. We discuss method for controlled assembly of oppositely charged nanosheets using tri-block co-polymer F127 to tune their interactions and study the synthesis and anion exchange of Mg-Al, Zn-Al and Co-Al layered double hydroxides. We characterize their structural, thermochemical, and ionic conduction properties to understand their fundamental behavior for applications as anionic conductors in electrochemical systems operating between 100-250 °C.

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