Nanotechnology: Richard Smalley
A carbon copy of the real thing

The high school student in Kansas City, Mo., was unimpressed when a teacher stated that carbon, as the basic building block of life, was the most important element in the periodic table. "My attitude was: 'Just look at all the interesting atoms in that region of the periodic table; certainly the reason that carbon dominates chemistry is our own ignorance,' " Richard Smalley recalls.

Smalley was looking forward to participating in the development of exotic new chemistries based on other elements-heady ideas such as silicon life forms, which were being discussed as a real possibility at the time. However, there is an irony in that early take on his career. Right from the start, the unique properties of carbon began to shape and dominate his research, leading eventually to a Nobel Prize in chemistry for the discovery of Buckminsterfullerene, an elemental form of carbon.

Smalley went on from high school to receive a BS from the University of Michigan and, in 1973, a PhD from Princeton University. During postgraduate work at the University of Chicago, he pioneered supersonic beam laser spectroscopy. "During that time, after developing apparatus that allowed us to literally stick any atom in the periodic table to any other atom, gradually what we found-right in your face-was that carbon is absolutely unique," he said.

After moving to Rice University (Houston), Smalley developed techniques for creating and measuring small clusters of atoms. He created a special laser-supersonic cluster beam apparatus that could vaporize any material and then analyze the size of the clusters that condensed from the plasma.

While that capability proved crucial to the discovery of Buckminsterfullerene, the actual discovery was catalyzed by an experiment proposed by Harold Kroto at the University of Sussex in England. Kroto specialized in microwave spectroscopy, as did Robert Curl Jr., one of Smalley's collaborators at Rice.

The technique had become a critical means of analyzing chemical components of interstellar gas clouds and the atmospheres of stars. Kroto wanted to know what happened to carbon in the atmosphere of carbon-rich stars when it condenses in a vacuum, and Smalley's apparatus was the perfect environment to simulate the process. Through Curl, Kroto scheduled a series of experiments with Smalley in which carbon would be vaporized and the resulting clusters analyzed.

Kroto arrived at Smalley's lab on Sept. 1, 1985, and the three scientists began to generate carbon clusters at high temperatures. Kroto had expected to find long carbon chains, but the experimental process instead generated stable carbon clusters in specific, even-numbered groups, with the number 60 being highly favored. The scientists hypothesized that the carbon, instead of forming long random chains, was able to wrap around itself somehow to create closed systems. Quickly, the three researchers concluded that the shape of the clusters must be a simple polyhedron. Kroto, long a fan of architect and visionary R. Buckminster-Fuller, was convinced that carbon was forming the same truncated icosohedron that formed the basis for geodesic domes.

The discovery verified Smalley's earlier idea that carbon was a totally unique element. But buckyballs are only one of an infinite variety of molecular architectures that can be generated by wrapping graphite sheets into closed structures. Each configuration has unique physical properties, and Smalley has since devised methods for creating such structures to order, hoping to seed a new industry based on carbon.

"Buckytubes" represent the strongest fibers that can be fabricated. "For example, if you take a sheet of paper, it may be very strong in tension, as a graphite sheet is . . . if you go off plane, it is very weak. It's also long been known that the solution to the problem is to wrap it around to make a tube," Smalley said. The tensile strength of the material translates into the stiffness of the tube, since any bending will stretch one side of the tube. On a nanoscale with a perfect molecular structure, the resulting fibers would be incredibly strong and could result in materials with an essentially new strength-to-weight ratio. Theoretically, they could be fabricated to any length, since the hexagonal carbon pattern can be extended indefinitely.

"This capability is unique for an element. Silicon cannot form into two-dimensional hexagonal sheets, and it can't form a benzene ring," Smalley said. At the molecular level, carbon is also the ideal electronic material, in his view. Depending on how the hexagonal pattern is aligned with the axis of the tube, the fibers can become nanoscale conductors, insulators or semiconductors. Smalley is looking for fabrication techniques that will first produce macroscopic fibers from the unique carbon chemistry of buckytubes, and further in the future, at methods for fabricating tubes with predefined sizes and electronic characteristics. "You can have them open or closed at the end and they can also be packed with other elements inside. I am sure that within a decade or so, you will be able to go to your favorite chemical-supply company and put in an order for your favorite type of buckytube."

Smalley's group already runs a small buckytube manufacturing service at Rice's Center for Nanoscale Science and Technology. "You can put in an order for purified nanotubes at about $2,000 a gram. With mass-production techniques, the price will come down," he said.

Smalley and his colleagues also are devising ways to attach additional elements to the side of the tubes, which could yield the ability to fabricate structures such as circuits. They have developed methods for cleaving the tubes at the ends to create pipes and tether them to gold balls.

"Research groups around the world are playing with these methods and I am sure that within a few years we will be seeing electronic circuits emerging," he said. "Of course, the next question is 'how good can it get'-can you build a computer that can rival what supercomputers can do in the next 20 years?" Theoretically, carbon-based electronic systems could support 1010 transistors on a square centimeter of real estate, and memories on the order of 1015.

"Could you do that in a repeatable process thousands of times? No way. But that isn't the dream. The dream is to go completely into a new game," Smalley said.

He envisions co-opting biotechnology to manufacture buckytube structures. The first step would be a "lipid" type membrane that could be wrapped around the outside of the tubes to make them compatible with the chemistry of living cells. Through genetic engineering, cells could then become assembly sites for buckytube networks. "You can begin to see how it would be possible to build machines of incredible complexity out of gizmos manufactured in this way," he said. Ultimately, that could lead to the manufacture of full-scale molecular brains.

Whatever course Smalley's program eventually takes, the versatile properties of carbon will propel him, and 21st-century industry, in some fundamentally new directions.

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