Date of Completion

4-17-2019

Embargo Period

4-15-2021

Keywords

Graphene Oxide, Polymers, Characterization, Nanocomposites, Seperation, Sensor

Major Advisor

Douglas H. Adamson

Associate Advisor

Richard S. Parnas

Associate Advisor

Yao Lin

Field of Study

Polymer Science

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

The conversion of graphite to graphene oxide (GO) is an effective and widely used method for solubilizing and exfoliating graphite. However, the oxidation is not uniform, and wide variations in the degree of oxidation exist between and within batches of GO. In this dissertation, we introduce an approach to both quantify the global degree of oxidation in GO and to separate GO into fractions, each with more uniform extents of oxidation. Using the formation of GO-stabilized oil-in-water emulsions, GO is separated into an emulsion fraction and a water fraction. The results find that the GO sheets that stabilize the emulsion droplets are less oxidized than sheets suspended in water as shown by multiple characterization techniques. The use of successive fractionation allows not only for the preparation of GO fractions with more narrowly defined properties but also provides a method for characterizing GO batches. Further, this fractionation method is applied to statistically determine the distribution of oxidation within a GO batch and used to calculate a number called oxidation dispersity (OD). Various properties of these GO fractions, such as optical, electrochemical, electrical, mechanical, and biocompatible were also investigated. Another study is focused on the changes occurring in GO sheets in different environments, like water or air, with time. The degree of oxidation and Raman defects appear to be changing as the GO ages. This phenomenon affects the outlook for GO applications and provides a better understanding of GO kept for storage. This fractionation method and aging study promise to provide the field with some critical missing pieces: a straightforward and standard method for the global characterization and comparison of GO made by different procedures, and the effects aging has on GO and its most important properties.

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