Date of Completion

4-24-2019

Embargo Period

4-22-2020

Keywords

quantum dot, gold nanoparticles, bacteriorhodopsin, hybrid nanosystems, plasmon, exciton, energy transfer

Major Advisor

Dr. Jing Zhao

Associate Advisor

Dr. Challa Kumar

Associate Advisor

Dr. Rebecca Quardokus

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Over the past two decades, there has been a burgeoning interest in the use of nanomaterials for device applications due to these systems displaying unique optoelectronic properties that are not seen on the bulk scale. One branch of nanostructures that has garnered attention is the field of quantum dots (QDs), which are nanoscale semiconductors that can absorb a broad, spectral range of light. Compared to traditionally used organic fluorophores, QDs exhibit numerous advantageous properties, such as high photostability, narrow emission peaks, and size tunability. There have been a profusion of studies exploring the interface between QDs with both inorganic and biological components, leading to the creation of hybrid materials for various devices. However, before such nanodevices can be materialized, a fundamental understanding of how the individual components interact with one another is vital to engineer successful device architectures. Hence, the aims of this dissertation work are to offer further insights into how QDs couple with other inorganic and biological systems. The first project investigates how modulation of the excitation wavelength of a laser source influences the exciton and plasmon interactions of QDs adhered to gold (Au) nanoparticles. By monitoring the photoluminescence decays of the hybrid Au/QD structures, we discover that there is a shortening in the photoluminescence lifetime when the excitation wavelength is on resonance with the plasmon resonance of the Au nanoparticles. Our work contradicts previous findings, and we attribute the uncommon behavior in our system to several factors. The second project of this dissertation focuses on the interaction between QDs and the transmembrane protein, bacteriorhodopsin (BR), which has been incorporated into multiple devices due to its robust nature and unique photochemistry. The objective of this work is to monitor the influence of QDs on specific photointermediates that comprise the BR photocycle using time-resolved absorption spectroscopy. Our experimental findings demonstrate variations in certain photointermediate lifetimes that would be beneficial to photochromic applications, and we propose a controversial mechanism to delineate our results.

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