Virginia Tech chemistry Professor Harry Dorn is a well known face in the world of carbon chemistry. His extensive work into fullerenes -- cage-shaped carbon molecules that come in different forms -- has yielded advances in MRI materials and the delivery of radioactive medicine. His previous worked revolved around how to reliable insert atoms of different types into an 80-atom carbon fullerene molecule. This cage allows for easy biological delivery of inorganic or radioactive compounds.
Now Professor Dorn has achieved another breakthrough that perhaps will prove equally significant. He discovered a new type of organic semiconductor based on fullerene.
He began with a normal 80 carbon fullerene, with 2 yttrium ions inside (Y2@C80) -- yttrium is a rare earth metal, but actually is rather abundant. It is found in uranium ore and throughout the Earth's crust. It is estimated that there is 400 times as much yttrium as silver on Earth.
After stuffing the carbon cage with yttrium, Professor Dorn took out one of the carbon atoms and replaced it with a single charged nitrogen. What he discovered was that the charge did not stay on the nitrogen, but migrated to the yttrium ions, forming an unusual single electron bond between them (Y2@C79N). He describes, "Basically, a very unusual one electron bond between two yttrium atoms."
Computational studies by Daniel Crawford, associate professor of chemistry at Virginia Tech, supported the existence of this unique molecule and x-ray crystallographic studies by Alan Balch, professor of chemistry at the University of California, Davis confirmed it. The research has shown that this is a whole new class of molecules, with atoms similar to yttrium likely to form similar bonds (general form : M2@C79N).
The research appears in the Sept. 6 edition of the Journal of the American Chemical Society (JACS).
Professor Dorn has since discovered that the electron can be removed from the fullerene cage. He states, "No one has done anything like this. Since the article was published, we now know that we can take the electron back out of the fullerene cage. The single electron bonded-diatomic yttrium has unique spin properties that can be altered. Increasing the polarization of this spin, could be important for improving the sensitivity of MRI and NMR."
Thus two intriguing uses of the new molecule arise. The first is to use it in the burgeoning field of quantum computing. Its ability to have the spin of the yttrium bonded electron altered could yield better quantum computers. Quantum computing focuses on, among other things, programming information into the spin of an electron, a field known as spintronics. This ultra-dense storage is seen as the future of computing.
A second intriguing possibility is to use the material as an organic semiconductor. Professor Dorn adds, "If we replace one of the carbon atoms with boron instead of nitrogen, we would be an electron short, instead of having an extra electron. Now you have the components of a semiconductor."
The benefits of such a semiconductor remain to be seen, but it would likely enjoy some of the same advantages as other organic semiconductors -- flexibility, strength, and ability to operate more easily in an organic environment.
Professor Dorn is excited about the discovery, but downplays its usefulness in the short term. He emphasizes this, and the continuing nature of the research, stating, "I don't down whether it is important yet or not. People have been working on adding a nitrogen atom to standard 60-carbon fullerene."