Tag Archives: carbon 60

Interstellar buckyball mystery solved

Caption: An artist’s conception showing spherical carbon molecules known as buckyballs coming out from a planetary nebula — material shed by a dying star. Researchers at the University of Arizona have now created these molecules under laboratory conditions thought to mimic those in their ‘natural’ habitat in space. Credit: NASA/JPL-Caltech

A ‘buckyball’, for anyone who doesn’t know, is a molecule made up of carbon atoms, Said to resemble soccer balls or geodesic domes, they’re also known as C60 or Buckminsterfullerenes as Rachel Abraham notes in her November 13, 2019 University of Arizona news release (also on EurekAlert),

Scientists have long been puzzled by the existence of so-called “buckyballs” – complex carbon molecules with a soccer-ball-like structure – throughout interstellar space. Now, a team of researchers from the University of Arizona has proposed a mechanism for their formation in a study published in the Astrophysical Journal Letters.

Carbon 60, or C60 for short, whose official name is Buckminsterfullerene, comes in spherical molecules consisting of 60 carbon atoms organized in five-membered and six-membered rings. The name “buckyball” derives from their resemblance to the architectural work of Richard Buckminster Fuller [bettr known as Buckminster Fuller], who designed many dome structures that look similar to C60. Their formation was thought to only be possible in lab settings until their detection in space challenged this assumption.

For decades, people thought interstellar space was sprinkled with lightweight molecules only: mostly single atoms, two-atom molecules and the occasional nine or 10-atom molecules. This was until massive C60 and C70 molecules were detected a few years ago.

Researchers were also surprised to find that that they were composed of pure carbon. In the lab, C60 is made by blasting together pure carbon sources, such as graphite. In space, C60 was detected in planetary nebulae, which are the debris of dying stars. This environment has about 10,000 hydrogen molecules for every carbon molecule.

“Any hydrogen should destroy fullerene synthesis,” said astrobiology and chemistry doctoral student Jacob Bernal, lead author of the paper. “If you have a box of balls, and for every 10,000 hydrogen balls you have one carbon, and you keep shaking them, how likely is it that you get 60 carbons to stick together? It’s very unlikely.”

Bernal and his co-authors began investigating the C60 mechanism after realizing that the transmission electron microscope, or TEM, housed at the Kuiper Materials Imaging and Characterization Facility at UArizona, was able to simulate the planetary nebula environment fairly well.

The TEM, which is funded by the National Science Foundation and NASA, has a serial number of “1” because it is the first of its kind in the world with its exact configuration. Its 200,000-volt electron beam can probe matter down to 78 picometers – scales too small for the human brain to comprehend – in order to see individual atoms. It operates under a vacuum with extremely low pressures. This pressure, or lack thereof, in the TEM is very close to the pressure in circumstellar environments.

“It’s not that we necessarily tailored the instrument to have these specific kinds of pressures,” said Tom Zega, associate professor in the UArizona Lunar and Planetary Lab and study co-author. “These instruments operate at those kinds of very low pressures not because we want them to be like stars, but because molecules of the atmosphere get in the way when you’re trying to do high-resolution imaging with electron microscopes.”

The team partnered with the U.S. Department of Energy’s Argonne National Lab, near Chicago, which has a TEM capable of studying radiation responses of materials. They placed silicon carbide, a common form of dust made in stars, in the low-pressure environment of the TEM, subjected it to temperatures up to 1,830 degrees Fahrenheit and irradiated it with high-energy xenon ions.

Then, it was brought back to Tucson for researchers to utilize the higher resolution and better analytical capabilities of the UArizona TEM. They knew their hypothesis would be validated if they observed the silicon shedding and exposing pure carbon.

“Sure enough, the silicon came off, and you were left with layers of carbon in six-membered ring sets called graphite,” said co-author Lucy Ziurys, Regents Professor of astronomy, chemistry and biochemistry. “And then when the grains had an uneven surface, five-membered and six-membered rings formed and made spherical structures matching the diameter of C60. So, we think we’re seeing C60.”

This work suggests that C60 is derived from the silicon carbide dust made by dying stars, which is then hit by high temperatures, shockwaves and high energy particles , leeching silicon from the surface and leaving carbon behind. These big molecules are dispersed because dying stars eject their material into the interstellar medium – the spaces in between stars – thus accounting for their presence outside of planetary nebulae. Buckyballs are very stable to radiation, allowing them to survive for billions of years if shielded from the harsh environment of space.

“The conditions in the universe where we would expect complex things to be destroyed are actually the conditions that create them,” Bernal said, adding that the implications of the findings are endless.

“If this mechanism is forming C60, it’s probably forming all kinds of carbon nanostructures,” Ziurys said. “And if you read the chemical literature, these are all thought to be synthetic materials only made in the lab, and yet, interstellar space seems to be making them naturally.”

If the findings are any sign, it appears that there is more the universe has to tell us about how chemistry truly works.

I have two links and citations. This first is for the 2019 paper being described here and the second is the original 1985 paper about C60.

Formation of Interstellar C60 from Silicon Carbide Circumstellar Grains by J. J. Bernal, P. Haenecour, J. Howe, T. J. Zega, S. Amari, and L. M. Ziurys. The Astrophysical Journal Letters, Volume 883, Number 2 Published 2019 October 1 © 2019. The American Astronomical Society. All rights reserved.

This paper is behind a paywall.

C60: Buckminsterfullerene by H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl & R. E. Smalley. Nature volume 318, pages162–163 (1985) doi:10.1038/318162a0

This paper is open access.

Where do buckyballs come from?

I’ve always wondered where buckyballs come from (as have scientists for the last 25 years) and now there’s an answer of sorts  (from the July 31, 2012 Florida State University news release Note: I have removed some links),

“We started with a paste of pre-existing fullerene molecules mixed with carbon and helium, shot it with a laser, and instead of destroying the fullerenes we were surprised to find they’d actually grown,” they wrote. The fullerenes were able to absorb and incorporate carbon from the surrounding gas.

By using fullenes  that contained heavy metal atoms in their centers, the scientists showed that the carbon cages remained closed throughout the process.

“If the cages grew by splitting open, we would have lost the metal atoms, but they always stayed locked inside,” Dunk [Paul Dunk, a doctoral student in chemistry and biochemistry at Florida State and lead author of the study published in Nature Communications] noted.

The researchers worked with a team of MagLab chemists using the lab’s 9.4-tesla Fourier transform ion cyclotron resonance mass spectrometer to analyze the dozens of molecular species produced when they shot the fullerene paste with the laser. The instrument works by separating molecules according to their masses, allowing the researchers to identify the types and numbers of atoms in each molecule. The process is used for applications as diverse as identifying oil spills, biomarkers and protein structures.

Dexter Johnson in his Aug. 6, 2012 posting on the Nanoclast blog on the IEEE (Institute of Electrical and Electronics Engineers) provides some context and commentary (Note: I have removed a link),

When Richard Smalley, Robert Curl, James Heath, Sean O’Brien, and Harold Kroto prepared the first buckminsterfullerene (C60) (or buckyball), they kicked off the next 25 years of nanomaterial science.

Here’s an artist’s illustration of  what these scientists have achieved, fullerene cage growth,

An artist’s representation of fullerene cage growth via carbon absorption from surrounding hot gases. Some of the cages contain lanthanum metal atoms. (Image courtesy National Science Foundation) [downloaded from Florida State University website]

 As I noted earlier I’m not alone in my fascination (from the news release),

Many people know the buckyball, also known by scientists as buckminsterfullerene, carbon 60 or C60, from the covers of their school chemistry textbooks. Indeed, the molecule represents the iconic image of “chemistry.” But how these often highly symmetrical, beautiful molecules with  fascinating properties form in the first place has been a mystery for a quarter-century. Despite worldwide investigation since the 1985 discovery of C60, buckminsterfullerene and other, non-spherical C60 molecules — known collectively as fullerenes — have kept their secrets. How? They’re born under highly energetic conditions and grow ultra-fast, making them difficult to analyze.

“The difficulty with fullerene formation is that the process is literally over in a flash — it’s next to impossible to see how the magic trick of their growth was performed,” said Paul Dunk, a doctoral student in chemistry and biochemistry at Florida State and lead author of the work.

There’s more than just idle curiosity at work (from the news release),

The buckyball research results will be important for understanding fullerene formation in extraterrestrial environments. Recent reports by NASA showed that crystals of C60 are in orbit around distant suns. This suggests that fullerenes may be more common in the universe than previously thought.

“The results of our study will surely be extremely valuable in deciphering fullerene formation in extraterrestrial environments,” said Florida State’s Harry Kroto, a Nobel Prize winner for the discovery of C60 and co-author of the current study.

The results also provide fundamental insight into self-assembly of other technologically important carbon nanomaterials such as nanotubes and the new wunderkind of the carbon family, graphene.

H/T to Nanowerk’s July 31, 2012 news item titled, Decades-old mystery how buckyballs form has been solved. In addition to Florida State University, National High Magnetic Field Laboratory (or MagLab), the CNRS  (Centre National de la Recherche Scientifique)Institute of Materials in France and Nagoya University in Japan were also involved in the research.