Assistant Professor of Chemisty
Charles Sykes | Tufts University
Adventures in the World of Nano
In the shrinking world of nanoeverything, chips the size of a human hair contain wires and switches much smaller than a single cell. An old device the size of a truck can now be built on a particle, smaller than a grain of sand. And in this realm, Charles Sykes is experimenting.
"Our latest project is molecular rotors," says Sykes, a surface scientist. "You can build nanoscale cogs and gears from individual molecules that rotate on a surface. We can cover an area smaller than a postage stamp with 1,000 billion rotors just by opening a valve."
In a typical experiment, Sykes says, he will put some molecules on a surface to study their natural rotation, with each molecule spinning around a center bearing. "Once it's hot enough, it will spin," he says.
If you can't see his point, it might be that you lack a supermicroscope. At Tufts University, Sykes, an assistant professor of chemistry, uses one of the most powerful tools for the study of surfaces, a delicate instrument called a scanning tunneling microscope (STM), invented in 1981 by IBM, to capture images of molecules and even manipulate individual atoms.
When Sykes was working on catalysis and surface science in a Ph.D. program at Cambridge University, the group had one of the first low-temperature microscopes, when there were about 10 in the world. As quickly as physicists had developed the scopes, he and other chemists started using them to look at chemistry on a smaller-than-ever scale.
At Cambridge, he says, his group was trying to understand how catalysts worked. "I was looking at tiny particles of gold, just four nanometers wide," he says. "You could only see them with the new microscope." Gold in jewelry seems solid, stable, but the new microscope showed tiny particles of gold were quite active. "Our goal was to understand how the nanoscopic gold surfaces sped up reactions and behaved as good catalysts," Sykes said.
At Tufts, he studies molecular behavior in systems like organic molecules on metal surfaces. "We have actually found if you add molecules of styrene, the stuff that your coffee cup is made of, it made all the atoms in the top of a gold surface move around quite rapidly," he says. "They are destabilized. If that's what you want in a catalyst, mobile atoms, you are on the right track."
He is also investigating how certain molecules assemble themselves, based on their charges. Organic molecules form intricate patterns once added to a metal surface. The microscope allows the researchers to watch the assembly in real time. Sykes and his group can decrease the temperature inside the microscope to 7 degrees Kelvin (minus 266 degrees Celsius below freezing) to slow down the motion of the molecules so they can view the assembly and make "movies" of how the molecules interact.
The assembly of special "polar" molecules that have an uneven charge distribution are of particular interest to the Sykes group. "It may be a new way to store information," he says, "in ferroelectric memory. Because molecules can flip up and down on the nanoscale, you can assign them a zero or a one. If we could devise a system based on individual molecules, you could have a million gigabytes on a chip the size of a postage stamp."
In his research, Sykes says "the possibilities are endless." Welcome to the world of nanoeverthing.
Education Component
The Cottrell grant will let Charles Sykes and his graduate students visit schools with a miniature version of his microscope for demonstrations. He plans to make use of new briefcase-sized scanning microscope, one that lets students see atoms and molecules. He uses a piece of graphite; one centimeter square for the demonstrations. He makes it smooth by taking off a layer of graphite - "It's like baklava; you just peel it away" - and puts it under the microscope. The image projects on a screen and shows the students the individual atoms of graphite, which look like a honeycomb structure, perfectly hexagonal, "like a nice fruit and vegetable stall, everything packed neatly," Sykes says. Images of atoms and molecules are extremely visually appealing, and help make abstract concepts like atomic theory easier for students to understand.
The Cottrell grant will also subsidize visits by high school teachers to Tufts, to work out demonstrations and experiments they can take back to their schools. "We'll be able to reach a lot more children this way," says Sykes. The teachers will be able to visit the Sykes Lab in the Pearson Chemical Laboratory at Tufts, in Medford, Mass., about five miles north of Boston.
