Author ORCID Identifier

https://orcid.org/0000-0002-2046-0069

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Chemistry

First Advisor

Dr. Beth S. Guiton

Abstract

This project was motivated by an in situ heating experiment in the transmission electron microscope (TEM) in which gold (Au) nanoparticles were observed to dissolve tin dioxide (SnO2) nanowires (NWs) under vacuum. The explanation for this observation was that the high-temperature and low-pressure environment of the TEM caused the reverse reaction of the well-known vapor-liquid-solid (VLS) method commonly used to grow NWs. In the VLS process, a metal catalyst absorbs reactant vapor until it becomes supersaturated. The precipitation of the NW occurs at the liquid-solid interface, which ceases when there is no longer reactant vapor, and the diameter of the NW is determined by the diameter of the original catalyst. The reverse process, the solid-liquid-vapor (SLV) method occurs when atoms in a solid NW diffuse into the metal catalyst. Eventually, the metal catalyst becomes supersaturated and the vapor escapes at the liquid-vapor interface. In this dissertation we demonstrate the combination of the SLV and the VLS mechanisms to create embedded heterogeneous interfaces in a variety of metal oxides. Metal catalysts are first used to etch metal oxide surfaces producing hollow channels that we term “negative nanowires”, and after etching the metal catalyst is reused to grow a NW of a different material from within the channel to form a crystalline interface. Understanding the chemical structure at these interfaces is both crucial and fascinating because diverse materials may interact in a variety of ways, including atomic mixing of the two structures and/or the formation of an abrupt crystalline interface or gap. We present our approach, therefore, towards gaining a comprehensive understanding of the structure-function relationship of these materials, focusing on particular on the interfacial region, to allow the design of new nanomaterials with tailored functionality.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.374

Funding Information

National Science Foundation (NSF) CAREER award Division of Materials Research (DMR) award number 1455154

Funded my research project 2014-2020

Available for download on Monday, August 29, 2022

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