Doctoral Dissertations

Date of Award

8-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

John Z. Larese

Committee Members

Sharani Roy, S. Michael Kilbey, Norman Mannella

Abstract

Today’s energy needs are presenting challenges which have to be addressed with novel, as well as sustainable and efficient solutions. Within this context, the family of metal oxide (MO) materials offers a broad diversity of both structural and physicochemical properties, along with great versatility of synthesis. Nanoscale MO particles can be decorated with other nanoparticles, particularly of metals, and new properties may arise from such combinations. The present dissertation work reports the details of the development of an experimental method to accomplish the decoration of MO materials with metal species originated by an effusive source, along with the characterization of the decorated materials’ properties. A custom-made vacuum chamber was optimized with several components (e.g. a calibration sensor to measure the effusive beam’s flux; a conical vessel to mix and expose the MO powders to such beam) and utilized to produce different decorated materials. The pure MO materials were synthesized as high-quality, size-selected particles with a patented method.Due to their different structure and optoelectronic character, magnesium (MgO) and zinc (ZnO) oxide were chosen as substrates to explore this novel decoration process; while copper, nickel and cobalt were selected as the decorating metal species, offering the opportunity to study not yet fully understood transition metal electronic properties. The several examples of newly formed materials were characterized using different techniques, in particular X-ray diffraction, photoluminescence and diffuse reflectance spectroscopy (reflectance was then converted into absorbance). These techniques revealed trends in some properties of the novel materials, and were paired with more microscopic probes, namely magnetization and electron microscopy measurements. Great emphasis was put on the Cu/MgO system. In particular, Z-contrast scanning transmission electron microscopy has shown clear presence of metal deposits of copper on the MgO surfaces, confirming the results gained with the previous techniques. Furthermore, a computer code was developed to facilitate the pore size distribution analysis obtained on mesoporous substrates. Several different materials were studied, in order to show the viability of the automated process, and the potential applicability of this method to studying porous structures for the same decoration process described earlier.

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