University of Maryland
Defect Chemistry of sp2 Carbon Lattices
Location: EB I Room 1011
Friday, April 19th 2013 - 11:00 am
Defects can rule the properties of a crystal. This effect is particularly intriguing in atom-thick materials such as single-walled carbon nanotubes and graphene, where new chemical and physical phenomena may arise due to strong coupling of electrons, excitons, phonons, and spins with defects in reduced dimensions. In this talk, I will discuss chemical strategies developed in my lab to address the challenge of understanding and controlling covalent functional defects on sp2 carbon lattices.
Covalent chemical reactions typically occur randomly on sp2 carbon lattices because electrons are delocalized. The modifications rapidly destroy the electrical and optical properties that make carbon-based materials desirable for many energy and electronic applications. We found that Billups-Birch alkylcarboxylation, a variant of the nearly century-old Birch reduction, occurs on sp2 carbon lattices nearly exclusively by defect activated propagation. This unexpected mechanism allows, for the first time, growth of "functional bands" on sp2 carbon lattices in a way reminiscent of crystal growth from a "seed". Implications of these findings to the applications of carbon nanomaterials (e.g., in creating a beaded-string silicon anode and chemical sensors) also will be discussed.
YuHuang Wang is an Assistant Professor of Chemistry at the University of Maryland. His research group focuses on materials and physical chemistry of carbon nanotubes, and their biomedical and energy applications. A central theme of his current research is exploiting defect chemistry of sp2 carbon lattices for understanding and controlling the coupling of electrons, excitons, phonons, and spins with defects in reduced dimensions. He is the author of 56 manuscripts and 16 patents and applications in the areas of carbon nanotechnology, nanofabrication and directed assembly. These works have been featured on 9 journal covers and by more than 40 news and perspectives in journals and news media, including Nature, Science, Chicago Tribune, and New York Times. He has received a number of awards, including an NSF CAREER award from the chemistry division in 2011.
Wang received a B.S. degree in chemistry from Xiamen University, China. He earned his Ph.D. with Richard E. Smalley at Rice University, where he demonstrated the first cloning of single-walled carbon nanotubes. He was also part of a team that developed the first macroscopic, neat, single-walled carbon nanotube fiber, an electrically conductive rival of Kevlar. He then joined the laboratory of Chad A. Mirkin at Northwestern University as a postdoctoral fellow, where he invented massively parallel dip-pen nanolithography for molecular printing and developed a fundamental understanding of directed assembly and manipulation of nanostructures.