June 20, 2011 — University-led consortium Semiconductor Research Corporation (SRC), SEMATECH, and The University of Texas at Dallas removed potentially toxic nano contaminants from a type of single-walled carbon nanotubes (SWCNTs).

Image. A single cell overlayed with the distribution in the cell of purified carboxylated single-walled carbon nanotubes (shown in yellow) as determined by laser scanning confocal Raman microscopy. Other experiments demonstrated that there was no apparent effect of the purified nanotubes inside cells on the ability of the cells to grow, whereas unpurified nanotubes inside cells inhibited growth by 60%.

SWCNTs are used in advanced nanoelectronics, as well as other industries that benefit from carbon nanotubes’ unique nano properties. The research team found that one functionalized SWCNT family, carboxylated single-walled carbon nanotubes (CSWNTs), reduced the ability of mammalian cells to grow in culture. This could signal toxicity. While small oxidized carbon fragments have been observed in prior research, this is the first suggestion that the fragments may be toxic.

Standard separation techniques removed the contaminating material, indicating that the purified nanotubes were not toxic, say researchers. The data suggests that specific organic impurities in CSWNTs may be responsible for much of the concern associated with the nano material. Continuing research will test this theory.

Removing the nano contaminants is "relatively easy," and practical to integrate to a semiconductor manufacturing facility, said Rockford Draper, Professor, Departments of Molecular & Biology and Chemistry at UT Dallas, adding that the contamination research could better inform companies buying and using CNTs.

The research is directed by SRC through the Center for Environmentally Benign Semiconductor Manufacturing, which anticipates and addresses future industry needs, with additional funding by the National Institute of Environmental Health Sciences.  SRC’s Center supports a major effort to understand, assess and screen emerging materials for their potential impact on environment, human health, and safety (EHS) prior to fab-level use. SWCNTs, which are an "emerging research material" listed in the International Technology Roadmap for Semiconductors (ITRS), are a perfect candidate for screening at the Center.

For more information and details about the research, see the forthcoming manuscript "Cytotoxicity Screening of Single-Walled Carbon Nanotubes: Detection and Removal of Cytotoxic Contaminants from Carboxylated Carbon Nanotubes" by Wang et al, that has been recommended for publication in Molecular Pharmaceutics.

SRC defines industry needs, invests in and manages the research that gives its members a competitive advantage in the dynamic global marketplace. For more information, visit www.src.org.