It appears that the hydrophobic, or water hating, carbon molecules clump together in water, forming aggregates of thousands of molecules. And there are reports that these aggregates can be toxic to microorganisms and even fish, should they escape from processing into surface water and ground water.
Now researchers at Virginia Tech have demonstrated that this behavior can be changed by the addition of citric acid – although the good news and bad news of this recent discovery has yet to be determined. They will report on their research to both environmental chemists and colloidal chemists at the American Chemical Society 235th national meeting in New Orleans on April 6 to 10, 2008.
“Our group and other research groups worldwide are examining what makes these fullerene aggregates tick and how they form,” said Peter Vikesland, associate professor of civil and environmental engineering at Virginia Tech. “Once they clump, they don’t settle out. People don’t know why they remain suspended. And we don’t really know how many molecules are in a clump. We use the term nC60 where N means some number that is extremely large.”
What Vikesland’s group has done that is different and novel is, instead of mixing the molecules with water, they have added citric acid, a naturally occurring and readily available acid. “The result is that instead of unstructured clumps, we get reproducible sphere-shaped aggregates,” he said.
They discovered, for example, that in the presence of a little bit of acid, which emulates the environment in the case of an accidental release of fullerenes, the aggregates are similar to those formed in water alone. But when more acid is added, the diameter of the aggregates becomes smaller. “We want to understand the implications of this finding to the toxicity, movement, and fate of fullerenes in the environment.”
Citric acid is well understood as a proxy for other kinds of organic acids, including those within cells. Some of the citrate-based spheres that Vikesland’s group discovered are similar to what happens intercellularly when human cells are exposed to C60, he said. “We think citrate and other organic acids with a carboxyl group make C60 more water soluble.”
Vikesland will present “Effects of small molecular weight acids on C60 aggregate formation and transport (ENVR 26)” to the Division of Environmental Chemistry at 1:35 p.m. Sunday, April 6, in room 235 of the Morial convention Center. Authors of the paper are Vikesland, civil and environmental engineering Ph.D. student Xiaojun Chang of Luoyang, Henan, China, and master’s degree student Laura K. Duncan of Augusta, Ga., and research assistant professor and TEM lab director Joerg R. Jinschek
Future environmental research will be done with simulated subsurface environments using a sand column to determine how these acidified masses move in ground water.
Vikesland will present Chang’s and his research about how C60 and citric acid interact to the Division of Colloid and Surface Chemistry on Wednesday, April 9, at 4:30 p.m. in 225 Morial Convention Center. He will present the results of various imaging analysis, such as atomic force microscopy. “We have no answers but we have a hypothesis, still unproven, that there are weak interactions between citrate and individual carbon molecules that cause the spherical shape,” Vikesland said.
The Vikesland group is exploring whether the C60-citrate interaction can be used to create reproducible shaped objects. Many fullerene-based products presently require solvents, which are then washed off. Unfortunately, the engineered fullerenes can retain solvents. Using citrate “is very green chemistry,” Vikesland said. “There are no solvents. It is a cleaner way to produce these things. Citrate may be an alternative.”
But there are challenges. “It’s not a hard bond but a weak attractive force, which makes these spherical aggregates challenging to work with. At the present time we don’t know how they will fall apart and what their products are,” Vikesland said.
In the meantime, the solvent issue aside, the current rush to put fullerenes into materials may not be wise “because we don’t understand what is going on,” said Vikesland. “If you have a face cream with fullerenes as an antioxidant – we don’t know how they will react. There are many organic acids in the environment.”
He concludes, “There are uncertainties. Everyone wants to prevent future problems.”
Susan Trulove | EurekAlert!
Scientists team up on study to save endangered African penguins
16.11.2017 | Florida Atlantic University
Climate change: Urban trees are growing faster worldwide
13.11.2017 | Technische Universität München
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.
Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...
Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
17.11.2017 | Physics and Astronomy
17.11.2017 | Health and Medicine
17.11.2017 | Studies and Analyses