Date of Graduation

7-2015

Document Type

Thesis

Degree Name

Master of Science in Chemistry (MS)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor/Mentor

Colin Heyes

Committee Member

Bill Durham

Second Committee Member

Jingyi Chen

Keywords

Pure sciences, Fret, Nanoscience, Quantam dots

Abstract

Quantum dots are a valuable tool in many research applications and commercial development. Their applications are far reaching and as such have become a topic of great interest. One of their greatest assets is the ability to utilize them as water soluble fluorescent labels. Rendering the nanocrystals water soluble can be accomplished in several ways, but one very popular method is by capping them with water-soluble multi-functional organic ligands. However, these ligands, when attached to the quantum dot surface, are labile and can be exchanged which can be problematic when using the quantum dots in research applications. This projects investigates the mechanisms of the exchange of surface bound ligands by employing modified fluorescent dyes as probes. The kinetics of the exchange is quantified by studying the quenching of the quantum dot signal as a function of time caused by bound dyes through Förster resonance energy transfer. Quantum dots with various ligands of different size, charge, and coordination are exposed to water-soluble dyes of different charges. Overall, it was discovered that a multi-component mechanism of exchange is present. The rate of the first very fast components provide insight into the initial binding of ligands to the surface, while the longer component(s) provides information about the exchange of ligands by dyes on the surface of the quantum dot.

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