Date of Award

June 2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Advisor(s)

Mathew M. Maye

Subject Categories

Physical Sciences and Mathematics

Abstract

Colloidal semiconductive quantum dots (QDs) are nanomaterials that have provoked much interest in the field of nanotechnology in recent decades. Due to the quantum confinement effect, these materials have highly tunable optical and electronic properties that depend on the nanocrystal size, shape, and composition. Because of these properties, QDs are potentially useful for applications such as LEDs, lasers, in-vivo and in-vitro imaging, and other sensing technologies. The work in this thesis has three central focuses: 1. the design, synthesis and characterization of CdSe/CdS core/shell quantum dots with rod-in-rod microstructures (QRs), 2. their use in bioluminescence resonance energy transfer (BRET) systems with firefly luciferase (Ppy) enzymes, and 3. the tuning of the surface chemistry and functionality of QRs and core/alloy magnetic nanoparticles (NPs) for other biological applications. In order to create BRET conjugates that participate in highly efficient energy transfer, I first synthesized a large variety of QRs and characterized them with ultraviolet-visible spectroscopy, photoluminescence spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, and other techniques. I investigated the effects of QR energy-accepting properties (absorption coefficients, quantum yields, and optical polarization), as well as morphological and topological characteristics (aspect ratio, microstructure and defect concentration), on BRET efficiency. In this work I also studied how different luciferase enzyme + substrate combinations could enhance BRET efficiency. Our findings indicated that QR with lower aspect ratios coupled with red-emitting Ppy enzymes had the highest BRET efficiency. Another BRET system that I studied involved a near infrared (nIR) emitting QD coupled with Ppy. This system had high BRET efficiency and showed promise for applications such as in-vivo imaging and night vision. Finally, I explored the silica coating of both QR and magnetic core/alloy FeNi and FeCr NPs. Silica coating is a surface modification tool which can greatly improve colloidal stability, render aqueous solubility, enhance and protect optical properties through surface passivation, and may mitigate the toxicity associated with the heavy metals used in the synthesis of QR and other NPs. In addition, since the silica (SiO2) shell thickness can be modulated in the synthesis, this modification can be used to probe distance dependence in BRET and to test magnetic behavior in NPs. I also employed these FeCr/SiO2 and FeNi/SiO2 NPs for magnetically and reversibly separating small fragments of DNA from solution. Both the FeCr/SiO2 and FeNi/SiO¬2 NPs showed good magnetic separation and promising capacity for DNA separation.

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