This dissertation examines the effects of phase transfers with thiol ligands on the optical properties of quantum dots (QDs) in water by investigating two systems: i) dihydrolipoic acid (DHLA)-capped PbS QDs and ii) thiolated DNA-capped core/shell CdSe/CdS QDs. QDs are bright, monodisperse, and tunable hydrophobic nanoparticles with high photoluminescence (PL) quantum yields (QYs). Phase transfers with thiol ligands impart hydrophilicity to QDs synthesized in organic solvents. However, these procedures often decrease the monodispersity, PL QY, and colloidal stability of the QD ensemble that makes QDs desired as Förster resonance energy transfer (FRET) donors or acceptors in biologically relevant environments. This work probes the relationship between an ensemble's polydispersity and its pH response after phase transfer. The bathochromic shifts of the PL of an ensemble of DHLA-capped PbS QDs can be entirely accounted for by FRET between QDs within aggregates. X-ray scattering techniques indicate that PbS-DHLA QD aggregates are mass fractals formed by clusters of tightly packed QDs in acidic environments. This work, expanding upon existing protocols, presents a new phase transfer method that employs a ternary solvent system to functionalize CdSe/CdS QDs with thiolated-DNA strands in less than one hour without intermediate ligands. This thesis provides insight into the challenges of deploying QDs in aqueous environments and highlights potential solutions.

Creator

• Schwabacher, James Ciro

DOI

• https://doi.org/10.21985/n2-geps-4770

Subject

• Physical chemistry
• Nanoscience

Language

• en

Alternate Identifier

• etdadmin_upload_753463
• http://dissertations.umi.com/northwestern:15179

Keyword

• phase transfer
• energy transfer
• fractals
• aggregation
• quantum dots

Date created

• 2020-01-01

Resource type

• Dissertation

Rights statement

• In Copyright