Factors Influencing Photoreactivity of Selected Single-Wall Carbon Nanotubes

R.G. Zepp, W-C. Hou, O. Okungbowa, D. Bouchard
U.S. Environmental Protection Agency, US

Keywords: nanotubes, transformation, photoreactivity

Summary:

Carbon nanotubes (CNTs) have a wide variety of potential and demonstrated applications, and the manufacture of these materials is rapidly growing. Single-wall carbon nanotubes (SWCNTs) are one important class of CNTs that can be structurally conceptualized as a one-atom-thick layer of graphene wrapped into a seamless cylinder of sp2-hybridized carbon atoms arranged in repeating aromatic rings. The rapid increase in usage of CNTs has prompted research on the transformation, transport and toxicology of these compounds in the environment. SWCNTs strongly absorb sunlight and photochemical reactions are one potentially significant pathway for transformations of these compounds. Here we provide new data and relationships on factors that affect the light-induced transformations of SWCNTs obtained from several sources. Th SWCNTs selected for this study were produced by four typical synthetic processes and thus are representative of the SWCNTs commonly used in many recent studies and applications. These were dispersed in aqueous media by sonication in the presence of surfactants (SDS, deoxycholate, and SDBS). Our results show that the direct photoreactivity of pristine SWCNT is generally low; however, indirect photoreactions involving hydroxyl radicals may be a significant transformation pathway in natural aquatic environments.