Date of Award

Spring 2023

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Andrew B. Greytak

Abstract

Colloidal semiconductor quantum dots (QDs) have been extensively investigated due to their attractive properties such as size-tunable absorption and emission spectra, large molar extinction coefficients, and significant photostability. These properties make them promising candidates for optoelectronic, photocatalytic, and biomedical applications. Common synthetic procedures of QDs produce nanocrystals capped with long-chain fatty acid derivatives which are stabilized in high boiling point solvents. Especially for bioimaging applications, the exchange of these native hydrophobic ligands with hydrophilic ligands should be performed, while preserving the smaller hydrodynamic radius. The coordination environment and thermodynamic parameters of the ligand exchanges should be carefully investigated to engineer improved ligand architectures to stabilize QDs in polar environments. The main focuses of this dissertation are to find ideal candidates and optimal conditions for QD ligand exchanges and investigate the binding strengths of small-molecule and polymer ligands for robust surface coatings. I will first describe the general background of the QDs including their applications, synthesis, purification, thermodynamics, and the chemistry behind the ligand exchanges. Then I will further describe the coordination environment of QDs in polar solvents using small-molecule imidazole ligands. The usage of isothermal titration calorimetry (ITC) to investigate thermodynamic parameters associated with the QD surface will be discussed in the final chapter using polymer ligand architectures. These investigations will help us improve bioimaging applications of QDs.

Rights

© 2023, Nuwanthaka Prasad Jayaweera Millaniyage

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