Graphene is a single atomic layer of carbon with extraordinary properties including exceptionally high electronic carrier mobilities, thermal conductivity, and mechanical strength
. Researchers are rapidly developing graphene-based applications in high-speed electronics, chemical and biological sensing, optoelectronics, and energy storage and conversion to take advantage of these behaviors. In all these applications, the chemical interaction of graphene with other materials plays a crucial role, and needs to be characterized and manipulated at the atomic level. The chemical functionalization of graphene via organic chemistry is actively being pursued for a variety of goals, including modifying its doping level and electronic structure, altering its affinity toward various organic, biological, and inorganic materials, and increasing its processability.
In this talk, I will describe my work on the chemical functionalization of graphene via two different approaches. First, I will discuss self-assembled monolayers of organic molecules that are physisorbed on the surface of graphene and characterized using atomic resolution scanning tunneling microscopy (STM). These monolayers, formed from perylene-based organic semiconductor molecules, have excellent long-range ordering with patterns that depend on intermolecular interaction forces that are not disrupted by surface defects in the graphene. These organic layers also serve as high quality seeding layers for the atomic layer deposition (ALD) of oxides, which play important roles in graphene electronics. Second, I will describe the direct covalent attachment of chemical groups onto the graphene lattice from diazonium salts. The chemical reactivity of graphene toward this reaction is found to depend strongly on the nature of the underlying substrate, as shown by Raman spectroscopic mapping. Covalent chemical schemes can also be exploited to robustly tether proteins to the graphene surface. Finally, I will also discuss the spatial micro- and nanopatterning of graphene chemistry in both covalent and noncovalent functionalization schemes via scanning probe lithography and reactivity imprint lithography, which will enable new applications in electronic devices and chemical sensors.
Dr. Qing Hua Wang is currently a postdoctoral researcher in Chemical Engineering at the Massachusetts Institute of Technology. She obtained her Ph.D. in Materials Science and Engineering at Northwestern University in 2010 and her B.A.Sc. in Engineering Science at the University of Toronto in 2005. Her research is focused on the synthesis, characterization, and application of 2D nanomaterials, in particular studying the interactions of graphene with molecules and materials. Her research interests also include scanning probe microscopy, optical spectroscopy, self-assembly, and nanofabrication.