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Reaction in Action: Before and After Pictures at the Atomic Level



Courtesy of University of California–Berkeley

Imagine watching a chemical reaction in real time: atoms breaking bonds with their neighbors and forming new arrangements as heat or pressure changes. That's what scientists at the Lawrence Berkeley National Laboratory and University of California, Berkeley came close to achieving in these images. Using an atomic-force microscope the researchers captured before and after images of a big hydrocarbon molecule—26 carbons with just 14 hydrogens tagging along—rearranging its shape as the heat rose from 270 degrees Celsius below zero to 90 degrees Celsius.

Once the atoms had rearranged themselves into a more compact structure in the heat, the researchers cooled things back down to 270 degrees Celsius and used an atomic force microscope to see what they had done. Atomic force microscopes work by running a single molecule across the surface of whatever is being viewed; the molecule-probe is deflected by the surface of the molecule being viewed. In this case, a carbon monoxide molecule probed the more complicated hydrocarbon. The result, as you can see, is reminiscent of the classic molecular structure diagrams familiar from chemistry textbooks, which is not visible via other types of microscopes or imaging techniques. The image even reveals the strength of the bonds between atoms, among other information.

This is more than a parlor trick. If chemists can see specifically how molecules restructure themselves, they may be able to reveal some of the secrets of catalysis—reactions sped up or slowed down by the addition of particular elements. In this case, the researchers hope to knit together big hydrocarbon molecules into sheets of the nanoscale carbon wonder material known as graphene. They might also have inadvertently shed more light on the sometimes dark art of catalysis, and opened up a new window for chemistry.

The views expressed are those of the author and are not necessarily those of Scientific American.

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