THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Friday, April 28, 2017

2:00 PM
in MOSE 2100F

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Young Jun Yoon

"Strategies for Metallic Nanoparticles, Metal Chalcogenide Nanocrystals and Perovskite Quantum Dots and their Optical and Optoelectronic"

Committee Members:

Dr. Zhiqun Lin, Advisor, MSE

Dr. Vladimir Tsukruk, MSE

Dr. Dong Qin, MSE

Dr. Blair Brettmann, MSE

Dr. Yulin Deng, CHEME

Abstract:

Nanocrystals with precisely tuned dimensions, spatial composition, and surface chemistry offers unique properties that may not be realized otherwise. This proposal takes on two distinct preparative approaches to craft such nanocrystals and explore their unique size and shape-dependent optical and optoelectronic properties.

The first approach utilizes star-like copolymers with distinct polymer blocks as nanotemplates to create nanostructured materials with precisely tuned dimensions and enhanced stability that cannot be achieved via conventional methods. In this phase of the project, we synthesize cesium-based perovskite quantum dots (CsPbX3 QD), gold nanoparticles (Au NPs), and silver nanoparticles (Ag NPs) with  tailored dimensions that are intimately and permanently tethered with polymers by capitalizing on rationally designed star-like block copolymer poly(acrylic acid)-b-polystyrene (PAA-b-PS) as nanoreactors. By synthesizing the copolymer blocks with low polydispersity via atom transfer polymerization (ATRP), we accurately control the size of CsPbX3 QDs and Au NPs, thus allowing strict control over light harvesting (CsPbX3 QDs & Au NPs) and emission (CsPbX3 QDs) at desired wavelengths in the visible region. Moreover, by manipulating the length of permanently tethered polymers, we improve their dispersion (CsPbX3 QDs & Au NPs) and water stability (CsPbX3 QDs).

The second approach capitalizes on the binding site, binding strength, and steric hindrance of oligomeric ligands to control the growth of various nanocrystals. Moreover, through post-modification via click chemistry, we further improve the surface functionality of nanomaterials. In this phase of the project, we prepare metal chalcogenide nanocrystals (CdSe, CdSe/ZnS, CdSe/Cd1-xZnxSe1-ySy/ZnS) and perovskite (CsPbX3) nanocrystals with high quantum yields, tuned emission wavelength, and excellent long term stability for use in lasing, light emitting diodes, scintillators, and shock sensors.

Future work will include the use of bottlebrush-like block copolymers with distinct polymer blocks as nanotemplates to create one-dimensional nanomaterials that cannot be realized via conventional methods. We aim to craft perovskite nanorods, perovskite nanotubes, gold nanorods, and gold nanotubes that have tailorable dimensions and permanently tethered polymers as ligand by utilizing bottlebrush-like block copolymer PAA-b-PS and PS-b-PAA-b-PS as nanoreactors.