THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Tuesday, February 13th, 2018

9:00 AM
in MoSE 3201A

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Jae Wan Ahn

"Rational Design and Synthesis of Silver-Based Bimetallic and Trimetallic Nanocrystals for Plasmonics and Catalysis"

Committee Members:

Prof. Dong Qin, Advisor, MSE

Prof. Zhiqun Lin, MSE

Prof. Meilin Liu, MSE

Prof. Joseph Sadighi, CHEM

Prof. Preet Singh, MSE

Abstract:

Manipulating the elemental composition of noble-metal nanocrystals provides a powerful means to tailor their properties for applications in plasmonics and catalysis. To this end, bimetallic and trimetallic nanocrystals have received considerable interests in recent years owning to the considerable number of possible variations in terms of elemental combinations and their spatial distributions. As a major advantage over the monometallic system, the involvement of two metals offers many opportunities to enhance their catalytic performance and optical properties, in addition to the creation of new capabilities. For example, we demonstrated that the inclusion of a second metal such as Pt and Pd on Ag nanocrystals could integrate both plasmonic and catalytic properties in a single nanocrystal. Many other groups have reported that both the electrochemical reduction and oxidation reactions catalyzed by Pd-Pt bimetallic nanocrystals could be substantially enhanced relative to either Pd or Pt nanocrystals by tuning the electronic coupling between these two metals.

The central objective of this thesis proposal is to develop a scientific basis for design and synthesis of Ag-based bimetallic and trimetallic nanocrystals for applications in plasmonics and catalysis. Specifically, I will work on the proposed research in three major thrusts. Firstly, I will design and synthesize Ag-based bimetallic nanocrystals with enhanced plasmonic properties by introducing concavities into the morphology, together with chemical stabilities arising from Au. I will report my recent development of a new strategy for transforming Ag nanocubes into concave nanocrystals encased by Au-Ag alloy frames by facet-selective carving and co-deposition. I will demonstrate that the enhanced plasmonic properties of Ag-Au concave nanocrystals towards in-situ SERS monitoring of the reduction of 4-nitrothiophenol to 4-aminothiophenol. Secondly, I will further introduce a third transition metal, such as Pt, Pd, Ir, Ru, or Rh to Ag-Au bimetallic concaved nanocrystals for the generation of trimetallic nanocrystals with high-index facets integrated plasmonic and catalytic properties. Combined with surface-enhanced Raman scattering (SERS), I will work on a new paradigm for ultrasensitive detection of single catalytic atom on the surface of Ag by using isocyanide-based SERS molecular probe. Finally, I will develop a droplet-based platform for the large-scale syntheses of Ag-based bimetallic and trimetallic nanocrystals, moving the batch synthesis up to mass production of nanomaterials for potential industrial applications.