Magazine article Science News

Taking Apart a Single Molecule

Magazine article Science News

Taking Apart a Single Molecule

Article excerpt

Taking apart a single molecule

The scanning tunneling microscope, invented only a few years ago, is already an important tool for obtaining images that reveal the locations of individual atoms on surfaces (SN:10/25/86, p.262). Lately, scientists have also been investigating the use of the same apparatus for altering surface structures and for manipulating matter at the atomic level. Now a team of researchers at the IBM Almaden Research Center in San Jose, Calif., reports success in pinning small organic molecules to a graphite surface. The researchers also have evidence indicating that they were able to split a pinned molecule into smaller pieces - perhaps the most delicate chemical surgery yet performed.

"We've all learned about molecules in school," says John S. Foster, who led the research. "We'd like to see them firsthand, and we'd like to try to take them apart and put them back together firsthand. That's the ultimate goal."

The key component of the scanning tunneling microscope is an extremely sharp needle that rides just above the surface being scanned. As the needle skims the surface, electrons flow between surface atoms and the needle. By continually adjusting the needle's height to keep the current constant, researchers obtain an image of the surface.

Foster and his colleagues found that by applying a brief electrical pulse-about 4 volts for 100 nanoseconds-through a needle dipped into a small liquid droplet lying on a graphite surface, they could pin individual organic molecules such as phthalates (see molecular model shown in top photograph) to the surface. …

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