Publication Date

2022

Document Type

Dissertation/Thesis

First Advisor

Li, Tao

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Chemistry and Biochemistry

Abstract

Catalysts are used in an extremely broad range of systems including everything from biological systems to industrial processes. An ideal catalyst offers robust stability and high activity. This work focuses on the synthesis and characterization of materials that show promise in the field of catalysis. Advanced synchrotron characterization techniques and unique experimental design are highlighted to provide foundation work that will provide the necessary information to aid in designing and fabricating catalytic materials. Supported metal nanoparticle (SMN) catalysts are enormously crucial for many catalytic applications. However, catalyst deactivation, caused by sintering and coke formation, is a ubiquitous problem that significantly undermines catalytic processing economics. The application of material overcoating onto supported metal nanoparticles by atomic layer deposition (ALD) offers the solution to inhibit catalyst deactivation. This dissertation discusses examples in which ALD has been used to stabilize SMN catalysts in gaseous and aqueous phase reactions. Various techniques are introduced to understand better how to characterize the overcoating layer and catalyst itself. Advanced characterization methods such a small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS) are utilized to monitor changes to the metal catalyst and ALD overcoating. In situ experiments were performed to monitor changes as a function of temperature. These experiments outline how the formation of pores in the ALD overcoating can be controlled by altering the heating rate and overcoat thickness. Enzyme immobilization techniques are widely researched due to their wide range of applications. Polymer–protein core–shell nanoparticles (CSNPs) have emerged as a promising technique for enzyme/protein immobilization via a self-assembly process. Different sizes and distributions of the polymer–protein CSNPs may be required based on the desired application. This work systematically studies the assembly process of poly(4-vinyl pyridine) and bovine serum albumin CSNPs. Average particle size was controlled by varying the concentrations of each reagent. Particle size and size distributions were monitored by dynamic light scattering, ultra-small-angle X-ray scattering (USAXS), small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). Results showed a wide range of CSNPs could be assembled ranging from an average radius as small as 52.3 nm, to particles above 1 µm by adjusting reagent concentrations. In situ X-ray scattering techniques monitored particle assembly as a function of time showing the initial particle growth followed by a decrease in particle size as they reach equilibrium. The results outline a general strategy that can be applied to other CSNP systems to control particle size and distribution for various applications. Bioactive core-shell nanoparticles offer the unique ability for protein/enzyme functionality in non-native environments. Researchers have sought to develop synthetic materials that mimic the efficiency and catalytic power of bioactive macromolecules such as enzymes and proteins for many decades. This research studies a self-assembly method in which functionalized, polymer-core/protein-shell nanoparticles are able to maintain bioactivity in a variety of chemical environments. TEM and dynamic light scattering (DLS) techniques were utilized to analyze the size and distribution of the CSNPs. The methods outlined in this research demonstrate a mild, green chemistry synthesis route for CSNPs, which are highly tunable and allow for enzyme/protein functionality in non-native conditions.

Extent

127 pages

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

Text

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