Colloidal semiconductor quantum dots (QDs) are inorganic nanocrystals that possess several unique photophysical properties, including tunable narrow emission and remarkable photo-
and chemical stability. They have large surface areas, and thus can be decorated with large numbers and a variety of molecular vectors. These properties combined offer a potentially
superior alternative to traditional organic fluorophore for advanced applications in bio-imaging and bio-sensing. Herein, our effort has centered on developing a series of metal
coordinating ligands with controllable structures to modify the QD surfaces and construct biocompatible nanocrystals. The ligand architecture accounts for several factors: (i) variable
coordination number, (ii) nature of the hydrophilic moiety, polyethylene glycol (PEG) or zwitterion, and (iii) versatility of end-reactive groups including amine, azide, carboxylic acid
and aldehyde. The ligand design is combined with a newly developed photoligation strategy to promote the dispersion of luminescent QDs in buffer media. The dissertation is organized in six
chapters: In chapter 1, we provide a brief introduction of the basic photophysical properties of QDs and the synthesis history for growing high quality semiconductor nanocrystals. We also
present some of the most effective methods reported to date to prepare aqueous QD dispersions, discuss the effective chemical coupling strategies for conjugating biomolecules, and review
the recent literatures that have used QD-bioconjugates for imaging and sensing purposes. In Chapter 2, we describe a novel photoligation strategy to promote the transfer of luminescent QDs
from hydrophobic to hydrophilic media using lipic acid (LA)-based ligands. We also discusse the experimental conditions, mechanismfor in-situ ligand exchange and the generosity of the
method towards the diverse functionality while maintaining the optical properties of the nanocrystals. In chapter 3, we present the design and synthesis of three sets of compact
zwitterionic ligands comprising either one or two lipoic acid (LA) groups chemically linked to a zwitterion moiety. These ligands are then combined with the photoligation strategy to
promote the phase transfer of QDs to buffer media. The high compactness and the stability of the nanocrystals over a broad range of conditions have been discussed.This chapter also
highlights the conjugation of mCherry to the QD surface via metal-histidine coordination, as a proof-of-concept, to develop FRET-based sensors. In chapter 4, we detail a versatile strategy
to prepare a series of poly (ethylene glycol) containing multicoordinating ligands optimized for the surface-functionalization of luminescent QDs and gold nanoparticles (AuNPs) alike. Our
chemical design relies on the modification of chiral L-aspartic acid precursor, and the advantages of using aminoacid combined with lipoic acid and reactive PEG moieties have been
discussed. Nonetheless, the two sets of ligands: bis(LA)-PEG-FN and LA-(PEG-FN)₂ described here are compatible with photoligation strategy to yield hydrophilic, colloidally stable and
reactive nanoparticles (QDs and AuNPs). In chapter 5, we discuss the preparation of hydrophilic QDs with intact azide (-N3) and aldehyde (-CHO) bio-orthorgonal functionalities on their
surfaces. Strain promoted click chemistry and hydrazine ligation will be discussed to illustrate the orthogonality of two reactive groups, azide and aldehyde. Additionally, we demonstrate
an optical method to extract the number of reactive -CHO groups per QD and finally estimate the total number of ligands bound to each QD for a few distinct size nanocrystals. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of
Philosophy. / Fall Semester 2015. / November 5, 2015. / Biocompatible, Bio-orthogonal, Ligand design, Photoligation, Quantum dots, Surface modification / Includes bibliographical references. / Hedi Mattoussi, Professor Directing Dissertation; Hengli Tang, University Representative; Gregory B. Dudley, Committee Member; Joseph B. Schlenoff,
Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_291284 |
| Contributors | Zhan, Naiqian (authoraut), Mattoussi, Hedi (professor directing dissertation), Tang, Hengli (university representative), Dudley, Gregory B. (committee member), Schlenoff, Joseph B. (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Chemistry and Biochemistry (degree granting department) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (188 pages), computer, application/pdf |
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