S t o r i e s by O P N
S e n i o r S t a f f Wr i t e r
Er ik K re i f e l d t . s c a t t e
OSA Fellow Wins Nobel Prize in Chemistry The Royal Swedish Academy of Sciences awarded the 1996 Nobel Prize in Chemistry to OSA Fellow Robert Cu r l , a professor of chemistry at Rice University. Cur l shares the award wi th chemistry professors Richard Smalley (Rice University) and Harold Kroto (University of Sussex, U.K.) . The scientists receive the award for their discovery of the unique structures of carbon atoms called fullerenes, which are closed carbon cages consisting of pentagons and hexagons.
"It couldn't have been done without lasers. We lean very heavily on them," says Curl . "We used lasers to vaporize the carbon to make the clusters and laser ionization to observe the clusters."
Cur l and his colleagues discovered fullerenes in 1985. Fullerenes are formed when vaporized carbon condenses in an atmosphere o f inert gas. Laser vapor izat ion
produces the gaseous carbon. Us ing a doubled, Q-switched, 532 nm Nd :YAG laser, the team d i rec ted pulses from a few mj to 100 mj at spot size of less than a millimeter at a carbon surface. The released carbon atoms are mixed with heliu m gas and form clusters. The gas is cooled to a few degrees above absolute zero and analyzed with time-of-fl ight mass spectrometry,
Robert Curl holds a model of a buckminsterfullerene. named after geodetic dome architect R. Buckminster Fuller.
using a 193 nm ArF excimer laser for photoionization. "It's opened up a whole new area of chemistry," says
C u r l . Thousands of papers have been publ ished on fullerenes. Several chemists had conceived of fullerenes, but without a simple way to make them, they remained an obscure concept. Since the award-winning experiment, several groups, lead by Krtchsmer and Huffman, have been able to make useful quantities of the molecules. "We basically stirred up the pot," he says.
Using fullerenes, it is possible to develop new materials with novel electrical and optical properties, sensors, polymers, and so on. W i t h its cage-like structure, a fullerene might be used "like a little atomic basket," Cur l says, where other atoms are put inside the structure of carbon atoms. The carbon protects the atoms in the basket, yet the atoms modify the properties of the carbon. A potential application is transporting a radioactive element inside the carbon structure to a targeted spot. This e l iminates concern that the radioact ive a tom w i l l become chemically bound to anything along its path.
Cur l and Smalley had been investigating Si, Ge, and GaAs clusters, look ing for insight into restructuring semiconductor surfaces and evidence of the formation of the semiconductor bandgap with increasing cluster size. Kroto came along wanting to look at carbon chains, hoping to gain insight into how carbon chain compounds might be formed when carbon is ejected from carbon stars. While investigating carbon chains, the scientists' attention turned to C 6 0 . "The new phenomena of C60 completely sidetracked us," Cur l says.
NIST sneaks a peek at monolayer formation
N IST researchers have produced the first images that illustrate how self-assembled monolayers form on a surface. The image of alkanethiol molecules assembling on a gold surface is the first with enough vertical resolution to show how the molecules pack together. NIST scientist Greg Poirier produced the image with a low-noise scanning tunneling microscope.
The image shows the 0.015 nm corrugated features of the gold surface, which are about 5% of the diameter of a gold atom. The linear features are islands of alkanethiol molecules, which are arranged in rows and aligned with the gold surface. Continued on page 8
A self-assembled monolayer forms on a gold surface. A very lownoise scanning tunneling microscopy system shows the process for the first time.
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