Seminar Series: Thursday, February 16, 2017 at 12:00 P.M.

JSNN Seminar Series

Title: “Block Copolymers and Plasmonic Nanoparticles for Energy and Sensing Applications.”

Speaker: Guoliang Liu, Ph.D.
Assistant Professor in the Department of Chemistry
Affiliated professor in the Department of Chemical Engineering.
Virginia Tech
Assistant professor of Nanoscience in the Academy of Integrated Science.
Affiliated to the Virginia Tech Center for Sustainable Nanotechnology and the Macromolecules and Interfaces Institute
Date and Time: Thursday, 2/16/2017, 12:00 P.M.
Location: JSNN Room 209

2907 E. Gate City Blvd., Greensboro, NC 27401

Abstract:

Block copolymers and nanoparticles are versatile materials that have rich chemical and physical properties. Here I present two examples of utilizing these materials to address challenges in energy and sensing applications.

In the first example, I will describe a method for controlling the pore size and structure in porous carbon after pyrolysis of a block copolymer, poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA). Using thermal or solvent annealing, we have systematically investigated its self-assembly behavior in both thin films and fibers. Surprisingly, the pore size and center-to-center spacing increase significantly with annealing temperature, different from most block copolymers. In addition, after self-assembly and pyrolysis of PAN-b-PMMA fibers, the resulting porous carbon fibers have hierarchical pores ranging from micro- to meso-, and to macro- length scales. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon instead of synthesizing block copolymers of various molecular weights and compositions. We have also developed a protocol for preparing porous carbon fibers with controlled porous structures.

In the second example, I will describe a comprehensive study of the sensitivity of plasmonic nanoparticles and their application in polymer brush sensing. After measuring and analyzing the sensitivities of >74 types of nanoparticles, we find that the aspect ratio is the key parameter that controls the nanoparticle sensitivity following an empirical linear relationship. Other parameters including shape, size, composition, and cross-sectional area have little effect on sensitivity. This finding contrasts with the conventional belief that shape is the most important parameter governing the sensitivity of plasmonic nanoparticles and inspires us to design simple nanoparticles for sensing. Based on this finding, we have introduced 2D Ag nanodisks as simple yet delicate nanoscale sensors to probe the polymer brush formation on surfaces and unveiled the underlying mechanism. Unitizing the unique plasmonic properties and intrinsically flat surfaces of 2D Ag nanodisks, we have demonstrated in situ the three-regime kinetics of polymer brush formation, and importantly, for the first time revealed the cause of a “latent regime” and what happens in the “latent regime”. The findings provide insight into the functionalization of plasmonic nanoparticles for polymer nanocomposites.

Biography:

Dr. Liu received his B. S. in Chemical Engineering from Zhejiang University, P. R. China in 2005, and his Ph.D. degree in Chemical Engineering from the University of Wisconsin-Madison under the supervision of Prof. Paul F. Nealey in 2011. Before completing his Ph.D. degree, his research in block copolymer lithography was recognized by Hitachi GST (San Jose, California), and he was recruited to apply his findings in magnetic data storage in 2010. Afterwards, he conducted postdoctoral research at Northwestern University (advisor, Dr. Chad A. Mirkin), where he was named an Outstanding Researcher in the International Institute for Nanotechnology.  He joined  Virginia Tech in Fall 2014 as an assistant professor in the Department of Chemistry and an affiliated professor in the Department of Chemical Engineering. He is also an assistant professor of Nanoscience in the Academy of Integrated Science. He is affiliated to the Virginia Tech Center for Sustainable Nanotechnology and the Macromolecules and Interfaces Institute, a Macromolecular Science and Engineering program at Virginia Tech. He is a recent recipient of the 2017 Air Force Young Investigator Award.