Nanoscale coordination polymers for biomedical applications and hybrid materials for solar fuel catalysis

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  • March 22, 2019
Creator
  • Dekrafft, Kathryn E.
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • This dissertation describes the design, synthesis, and characterization of hybrid materials and their evaluation for use in several biomedical and solar fuel applications. Most of the materials are nanoparticles based on coordination polymers (CPs), a class of highly tunable hybrid materials composed of organic bridging ligands linked together by metal ions. Nanoscale CPs (NCPs) have been developed for biomedical imaging contrast enhancement and for drug delivery. They have been designed to carry high payloads of diagnostic or therapeutic agents, and to overcome the disadvantages of conventional small-molecule agents by improved pharmacokinetics and biodistribution. NCPs containing elements with high X-ray attenuation have been developed for use as contrast agents for computed tomography (CT) imaging. NCPs based on an iodinated ligand or on Zr or Hf ions were synthesized, and their potential for CT contrast enhancement was demonstrated in phantom studies. The robust Hf-based NCPs were coated and functionalized to increase biocompatibility and performance, and were used for in vivo CT imaging. NCPs for drug delivery have been designed based on methotrexate, a molecular anticancer drug that is a first-line treatment for leukemia. The NCP approach to drug formulations offers a potential way to target and deliver high payloads of methotrexate to cancer cells. Photocatalytic and electrocatalytic materials have been developed toward the goal of storing harvested solar energy in chemical fuels by water splitting. A new CP-templated method has been developed for the synthesis of a metal oxide nanocomposite with interesting photophysical properties. Fe-containing NCPs were coated with amorphous titania, then calcined to produce crystalline Fe2O3/TiO2 composite nanoparticles. This material enables photocatalytic hydrogen production from water using visible light, which cannot be achieved by either Fe2O3 or TiO2 alone or a mixture of the two. Molecular Ir and Ru complexes were directly and covalently grafted onto carbon electrodes, for electrocatalytic water oxidation. The catalysts had enhanced rates and stability when grafted and driven electrochemically compared to being chemically-driven in solution. This strategy provides a way to systematically evaluate catalysts under tunable conditions, potentially providing new insights into electrochemical water oxidation processes and water oxidation catalyst design.
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  • In Copyright
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  • ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry.
Advisor
  • Lin, Wenbin
Degree granting institution
  • University of North Carolina at Chapel Hill
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