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THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Wednesday, June 16, 2021
10:00 AM
via
BlueJeans Video Conferencing
https://bluejeans.com/798504341/2384
will be held the
DISSERTATION PROPOSAL DEFENSE
for
Ruoqi Gao
“Metal-Sensitive Functionalization and Self-Assembly of Bimetallic Core-Frame Nanocubes”
Committee Members:
Prof. Dong Qin, Advisor, MSE
Prof. Josh Kacher, MSE
Prof. Zhiqun Lin, MSE
Prof. Meilin Liu, MSE
Prof. Angus Wilkinson, CHEM
Abstract:
Noble-metal nanocrystals have received great attention owning to their intriguing properties and emerging applications in areas including plasmonics, sensing, imaging, catalysis, and medicine. As demonstrated by ample examples, the functionality of nanocrystals in these and related applications can be greatly improved by changing from monometallic to bimetallic systems. Seeded growth offers a powerful route to bimetallic nanocrystals with a core-frame structure. This approach is built upon the concept that preformed nanocrystals can serve as seeds to direct the deposition of the second metal. In the first part of my proposal, I will use Ag nanocubes as seeds to generate Ag@M (M: Pd, Pt, Rh, Ir, and Ru) nanocubes with a core-frame structure by controlling the deposition of M atoms. In particular, I will elucidate the mechanistic details for the reduction and deposition of the second metal (M) on Ag nanocubes using an isocyanide-based molecular probe to monitor the initial stages of deposition by surface-enhanced Raman Scattering (SERS). In the second part, I will demonstrate the use of metal-selective surface functionalization and self-assembly for the fabrication of well-controlled catalytic nanoreactors featuring plasmonic hot spots for monitoring reactions in real time by SERS, with an ultimate goal to accelerate technological innovations through rational design of catalytic materials. My central hypothesis is that molecules bearing isocyanide and thiol end groups will selectively bind to the M and Ag regions on the Ag@M (M: Pd, Pt, and Ir) core-frame nanocubes, respectively, in an orthogonal fashion. As such, two core-frame nanocubes with M atoms confined to the edges will be brought together by a di-isocyanide linker to generate a catalytic nanoreactor while the Ag side faces will be covered by thiol-based reactants or other compounds that are physically confined inside the nanoreactor. For chemical reactions, I will initially focus on the hydrogenation of nitroaromatics for the production of thermodynamically unfavorable products such as hydroxylamine and azo compounds to demonstrate the premise of such a catalytic system in elucidating the mechanistic details involved in chemical transformations of industrial importance. I will further leverage the fingerprinting capability of SERS to investigate the bond-selective hydrogenation of cinnamaldehyde, a catalytic reaction pivotal to the production of fragrance, agrochemical, and pharmaceutical compounds. This research will not only enable real-time characterization of catalytic reactions but also shed light on the rational design of new or improved catalyst materials.
