Date of Award
Spring 2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Ofer Kedem
Abstract
Nanoparticles (NPs) are an exciting class of materials with unique properties that inspire their use in sensing, catalysis, optoelectronic devices, and more. NPs are frequently coated in organic molecules, termed ligands, to increase their stability, but ligands also influence NP catalytic activity and their interactions with neighboring molecules. To fully realize the potential of nanomaterials as key components in novel complex systems, a more nuanced understanding of the relationships between NPs, ligands, and their surrounding microenvironment is critical. After a brief review of the NP field in Chapter 1, Chapter 2 begins the investigation of structure-function relationships with a cross-class comparison of ligand effects on the catalytic activity of gold nanoparticles (Au NPs) immobilized on glass slides. This system enables the determination of the absolute effect of ligands in comparison to identical but bare NPs, since the removal of ligands from colloidal NPs leads to aggregation. Chapter 3 focuses on increasing the overall activity of NPs through specific ligand coatings, a concept not previously demonstrated in the literature since ligands are typically believed to hinder catalysis. Enhancement of NP activity toward reactions with anionic substrates is shown when Au NPs are coated with cationic polymers, likely due to electrostatic interactions. The results from both catalysis studies underscore the importance of considering catalyst-ligand-reactant interactions, and promote a ligand-focused approach to efficient catalyst design. Chapter 4 continues to investigate the relationship between surface modifications and NP function, with respect to directed assembly. The study introduces a procedure to functionalize quantum dots (QDs), semiconductor nanocrystals with tunable emission, with ligands that can participate in thiol-yne click chemistry. The functionalized QDs are deposited onto a substrate in complex patterns using a photopatterning approach. A fluorescence microscope harnesses light to trigger a reaction between the QDs and the surface of modified glass slides, resulting in controllable QD deposition. This is the first time that covalent bonding between QDs and a surface for the purpose of pattern generation has been presented in the literature, a critical building block for the fabrication of optoelectronic devices.