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 |
After
exploring for 25 years, scientists have solved the question of how the
iconic family of caged-carbon molecules known as buckyballs form.
The
results from Florida State University and the National Science
Foundation-supported National High Magnetic Field Laboratory, or MagLab,
in Tallahassee, Fla., shed fundamental light on the self-assembly of
carbon networks. The findings should have important implications for
carbon nanotechnology and provide insight into the origin of space
fullerenes, which are found throughout the universe.
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.
In the study, published in the peer-reviewed journal Nature Communications, the scientists describe their ingenious approach to testing how fullerenes grow.
“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.
FSU doctoral student Paul Dunk checks equipment during magnet time at the MagLab’s Ion Cyclotron Resonance lab. Image courtesy National High Magnetic Field Laboratory and National Science Foundation |
By
using fullerenes 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 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.
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.
Other research collaborators included the CNRS Institute of Materials in France and Nagoya University in Japan.
