Portland, Ore. Critics of nanotechnology have fastened onto speculation by Sun Microsystems co-founder Bill Joy about runaway nanobots turning the planet into "gray goo," tainting the technology in all its forms. Now, cooperating engineering teams at the Georgia Institute of Technology and Rice University are angling to find out if that's so. Their preliminary results in measuring the behavior of nanomaterials in the environment show that the threats are real, but so is the hope of preventive solutions.
A detailed study by the Georgia Tech and Rice researchers reveals that fullerene, one of the first nanomaterials, could threaten water supplies if not handled properly. In particular, nanoscale fullerenes were found to clump together in groundwater to form larger, micrometer-scale particles that could accumulate, gray-goo style. The researchers also found that saltwater broke up the clumps as well as various preparation steps that could be mandated by government regulators.
"To look at a material's potential as a pollutant, how to minimize its environmental impact and make the industry sustainable is really the right thing to do," said John Fortner, a Georgia Tech research scientist and a Rice University doctoral candidate. Fortner performed the work with Joe Hughes, chairman of the Georgia Tech School of Civil and Environmental Engineering, under the auspices of the Rice University Center for Biological and Environmental Nanotechnology.
Today, the U.S. Occupational Safety and Health Administration (OSHA) advises no special handling procedures for nanomaterials, because there has been no definitive research on what might be needed to keep the environment safe. For instance, fullerenes, or C60 popularly called buckyballs are related to their macroscopic relatives, carbon black. So OSHA advises handling fullerenes like carbon black.
"This research is providing the information to make practices sustainable when fullerene production comes online," Fortner said. Mass production of fullerenes, which are being proposed for everything from dry lubricants to energy conversion in semiconductors to drug delivery, is about two years away, he said.
The study has shown which factors affect the size of these aggregate particles and their ability to travel through, and become lodged in, the groundwater system. The researchers have also made a start at finding ways to treat fullerenes before they enter the environment.
"Most biological and environmental systems are based around water, but researchers thought fullerenes couldn't be transported in water, because they are virtually insoluble," said Fortner. "We thought they would simply stick to soil or other organic material. But our research shows this is not the case. When fullerenes, such as C60, come in contact with water, they form aggregates at the nanoscale."
The researchers used nuclear magnetic-resonance imaging as well as a transmission electron microscope to study the impact of clumped fullerenes. They cryogenically cooled the samples, then sliced them to characterize the parameters that determine particle size. They found that the fullerenes could clump into aggregate particles of 20 nanometers to 0.5 micron in diameter.
Using electron and powder diffraction techniques, the researchers found that the clumps retained nanoscale properties and formed into a crystalline structure. Changing the pH of the water from 5 to 9, they discovered, reduced the potentially hazardous particles to smaller, safer sizes. They also found that the rate at which the particles were dispersed into water affected the clumps' size essentially, the slower, the bigger.
The group also studied how the concentration of ions in groundwater affected the clumped particles' stability. The negatively charged fullerene clumps were found to break up and disperse harmlessly when the level of positive ions was raised. For instance, in freshwater the clumped fullerenes were found to transport unpredictably in the environment, but when the salt ions in the water were raised to the level of seawater, the clumps stopped transporting.