Examination of Metal Oxide Nanocrystal Formation, Growth and Applications using a Continuous Growth Synthesis
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Date
2022-10-04
Authors
Knecht, Tawney
Journal Title
Journal ISSN
Volume Title
Publisher
University of Oregon
Abstract
Metal oxide nanomaterials can serve as high-performance materials in many applications, but only if their nanoscale structure can be controlled through synthesis. Metal oxide nanocrystals with the necessary structural attributes (size, shape, crystallinity, dopant identity and concentration, defect structure, architecture, etc.) to enhance these applications have been produced, but little is known about growth processes that lead to those structures. Research on the nanocrystal growth process is necessary to gain the level of synthetic control required to predictably engineer the desirable attributes of nanocrystals.The research described in this dissertation utilizes a continuous addition synthesis that enables fine control over the nanocrystal growth process in examining the influence of precursor oxidation state, reaction atmosphere, precursor ligation, and reagent identity are investigated. In the case of cerium oxide, it was found that precursor oxidation state does not significantly influence the growth of cerium oxide nanocrystals. Instead, we find that reaction atmosphere (N2 vs air) drastically influences the nanocrystal structure, which in turn influences the growth, with nanoribbons or plates forming under N2, and nanocubes forming under air. We also found that acetate from the precursor starting material were
responsible for nanoribbon formation. For tin-doped indium oxide (ITO), it was found that changing the primary reagent from oleyl alcohol to oleylamine drastically influenced the nanocrystal growth by influencing the number of nanocrystals formed in the earliest stages of nanocrystal formation and growth.
Towards utilizing ITO nanocrystals in applications, we investigate their use as plasmonic filters and as electrocatalysts. We find that we can sculpt the absorption spectrum of solution-processed ITO nanocrystal films, enabling the fabrication of tunable IR filters. We also find that ITO nanocrystals are unstable and restructure to an indium/tin metal alloy under electrochemically reducing potentials required for CO2 reduction.
This dissertation includes previously published and unpublished co-authored material.