Leaky lab equipment and Virginia Tech researchers’ eagle eyes resulted in a new family of molecules with potential applications ranging from medicine to molecular computers and now being explored for use as lifesaving filters, such as in gas masks.
Researchers worldwide who were experimenting with the new form of carbon molecules called buckyballs, were mystified for about five years by a small peak in their mass spectrometry readouts, always 1109.
Discovered in 1985 and named after Buckminster Fuller, designer of the geodesic dome, buckyballs — also called fullerenes — are clusters of carbon with an even number of atoms arranged in hexagons forming a ball-shaped cage.
Scientists were trying to insert metals into the cages and to produce the structures in useful quantities. There had been some success in getting fullerenes to carry one or two metal atoms — but not with ease or in high quantity.
Then, a few years ago, Harry Dorn, Virginia Tech professor of chemistry, and Steve Stevenson, post doctoral fellow at Tech, created a new class of stable, filled buckyballs — and solved the 1109 mystery.
Dorn, Stevenson, and Greg Rice, the undergraduate operating the equipment, were trying to blast metals into the center of buckyballs by drilling holes in graphite rods, inserting metals, placing the rods in a sealed chamber, and burning them with an electric arc generator. The result of the process was a bunch of soot that then had to be separated and analyzed with much more sophisticated equipment — even sent to specialized labs.
First, high pressure liquid chromatography is used. The soot mixed with a solvent is passed over a treated surface that has an affinity for the buckyball or the metal inside of it, separating them from non-bucky soot. Then, a mass spectrometer is used to measure the mass to charge ratio, so you know the molecule’s size.
Nuclear magnetic resonance (NMR) is then used to identify atoms by the way their nuclei decay. At this point, a theoretician can create a model of the molecule. However, buckyballs are difficult to analyze because they are so symmetrical. So the researchers only knew they had buckyballs with their metals — usually easy-to-trace scandium — inside.
The 1109 peak was still unexplained.
“We decided to find out what it was,” recalls Dorn. “Steve and I took reams of data — NMR readouts, mass spec readouts, XPS (X-ray photoelectron spectroscopy) data — and went to (one of the food courts on campus). We spent two or three hours poring over it. After about the fourth cup of coffee, we had it narrowed down to the most likely material.”
Stevenson recalls, “He asked me, ‘What’s the second choice?’ and I said, ‘There isn’t any.’” The mystery material was nitrogen.
“Then everything made sense,” says Dorn. The equipment was letting atmospheric nitrogen into the chamber. “The arc disassociated it into nitride atoms. The metals latched onto the nitride — three atoms of metals onto one atom of nitride — and as it cooled, the carbon cage formed. So you have a molecule with a nonmetal core, the three metals, then the nonmetal cage.”
It was the first example of isolated four atom molecular clusters inside a buckyball, and the first example of such a cluster with a nitrogen atom at the center, Dorn reports. “It looks like a whirling Mercedes Benz emblem inside a ball,” he says.
The researchers had their coffee-induced epiphany in 1998. They fine-tuned and confirmed their findings, created materials on purpose and in useful quantities, and reported their discoveries in Nature. The final proof came as a result of innovative X-ray crystal analysis by Allen Balch at UC Davis. Instead of analyzing the buckyball crystal, he de-crystallized the metal and nitride filled buckyball by adding atoms to see what complexes resulted. Since he knew what he added, he then knew what the rest of the components were.
“It’s interesting that several other labs around the world had reported 1109. It was talked about at conferences for years. No one else realized what they really had,” says Dorn.
Maybe the discovery was meant for Dorn, whose campus address is 1109 Hahn Hall.