Spatially Controlled, Covalent Functionalization of Carbon Nanotubes for Retention and Generation of Desirable Electrical and Optical Properties
Monday, May 6, 2013
Alexandra H. Brozena, Ph.D., is a graduate research assistant at the Department of Chemistry and Biochemistry at the University of Maryland.
Abstract: Carbon nanotubes feature a unique combination of electrical, optical, and mechanical properties that make them highly attractive for a broad range of applications including nanoscale electronics, renewable energy, polymer composites, and biomedical imaging amongst many others. The breadth of these applications suggests the potential for accidental and significant introduction of these materials into the environment; the effects of which are not well known. However, one of the great obstacles to commercial applications this material faces resides in their highly insoluble nature which diminishes functionality and complicates processing. Covalent functionalization has become a common way of individually dispersing nanotubes to overcome these aggregation issues, although the implantation of chemical groups on the nanotube sidewalls causes a simultaneous loss of desirable electronic and optical properties by disruption of the delocalized pi-bonding electrons. We circumvent this tradeoff by controlling the location of carbon nanotube functional groups (using various highly scalable wet chemistries), to maintain significant tracts of pristine sp2 carbon surface to avoid scattering electrons and excitons, yet with enough sidewall functionality to improve water solubility. We demonstrate the retention of both conductivity and near-infrared photoluminescence after functionalization as well as the generation of new defect dependent photoluminescence emissions that are the result of nanotube doping. Understanding how covalent functionalization affects the carbon nanotube analytical signature will be discussed in the context of detecting these nanomaterials in the environment.