The basic theory of how chemical reactions happen--molecules approach each other, overcome potential energy, and then form new reactants--has held up in experiments almost every time. But the theory doesn't fully explain what happens when a molecule approaches a metal surface, such as the surface of an industrial catalyst. This is important because metal catalysts are widely used in catalytic converters, fuel cells, and even to make margarine.

What makes metals tricky is that they don't have discrete energy states like molecules--rather than jumping from one specific energy level to another, electrons move between energy states in a metal in a more continuous way.

Two papers published in the journal Science this week use new algorithms to better describe what happens at the surface of metals including catalysts.

One describes the interactions between a gold surface and nitric oxide molecules excited using a laser. Older models predict that when the gas hits the gold surface it will still be vibrating. The new model predicts what actually happens: the molecule electronically couples to the gold.

The second paper looks at the interaction that cause hydrogen atoms on a copper surface to bond with one another and form hydrogen gas. It remains to be seen whether these results can be generalized, but if they can it could lead to a better understanding of the metal catalysts widely used in industrial chemistry.

This image of pentacene, a molecule made up of five carbon rings, was made using an atomic-force microscope. Credit: Science/AAAS

Using an atomic-force microscope, scientists at IBM Research in Zurich have for the first time made an atomic-scale resolution image of a single molecule, the hydrocarbon pentacene.

Atomic-force microscopy works by scanning a surface with a tiny cantilever whose tip comes to a sharp nanoscale point. As it scans, the cantilever bounces up and down, and data from these movements is compiled to generate a picture of that surface. These microscopes can be used to "see" features much smaller than those visible under light microscopes, whose resolution is limited by the properties of light itself. Atomic-force microscopy literally has atom-scale resolution.

Still, until now, it hasn't been possible to use it to look with atomic resolution at single molecules. On such a scale, the electrical properties of the molecule under investigation normally interfere with the activity of the scanning tip. Researchers at IBM Research in Zurich overcame this problem by first using the microscope tip to pick up a single molecule of carbon monoxide. This drastically improved the resolution of the microscope, which the IBM scientists used to make an image of pentacene. They arrived at carbon monoxide as a contrast-enhancing addition after trying many chemicals.

The researchers hope that looking this closely at single molecules will give them a better understanding of chemical reactions and catalysis at an unprecedented level of detail.

The imaging work is described today in the journal Science.

The data encoding these words was carried as pulses of light on its journey from my computer to yours. But, as new research demonstrates, using light to carry encoded alphanumeric messages over long distances doesn't require computers, optical fiber, or even electricity.

By patterning flammable metallic salts on a nitrocellulose fuse, researchers at Harvard and Tufts University have encoded messages that can be transmitted without the need for a power source. When one fuse burns, the metallic salts along its length emit pulses of infrared and visible light of different colors whose sequence encodes, "LOOK MOM NO ELECTRICITY." The system, described today in the journal Proceedings of the National Academy of Sciences, is inspired by chemical information storage in biological cells.

David Walt, professor of chemistry at Tufts and Harvard's George Whitesides developed the infofuses in response to a call from the Defense Advanced Research Projects Agency (DARPA) for technologies to allow soldiers stranded without a power source to communicate. DARPA wanted "something that doesn't require any electronics or heavy equipment to lug around," says Walt.

Civilians stranded in a mountainous area without cell reception could use the infofuses, too, Walt says. His cell phone dropped our call a moment later. When he called back, I suggested maybe he needed an infofuse now. "That's the problem--it doesn't work over three thousand miles," he says. The group is now working on extending the range of the optics used to read the signal, which can currently be read from 600 meters away in bright ambient light using a CCD camera; Walt says 1.5 kilometers should be possible using the current optics. "We're [also] trying to figure out a way to dynamically encode a message on the fly in the field without specialized equipment," says Walt. So far they've used micropipetters and ink-jet printers to pattern the fuses.

Another cool technology recently pioneered by Whitesides is paper medical diagnostics.