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Naked molecule exposed

IBM Research - Zurich

Click for video: This graphic shows how scientists
used a carbon monoxide molecule on the end of a
metal tip to map a pentacene molecule. Click on the
image to watch a video from NBC's "Nightly News."


Scientists have traced the structure of a complete molecule in all its glory, using the sharpest pen ever devised: an atomic force microscope tipped with a single molecule of carbon monoxide.

The experiment, detailed in Friday's issue of the journal Science, could help open up a new frontier for molecular-scale circuitry and construction.

Researchers have been imaging molecules and their constituent atoms in crystals for decades, but the trick is to get a fine-resolution fix on the structure and behavior of an entire, self-contained molecule as it sits on a surface.

If you have the wrong stuff at the very tip of your probe, the very act of mapping the molecule can spoil the picture.

Leo Gross and his colleagues at IBM's Zurich Research Laboratory found that a carbon monoxide molecule (with its oxygen atom sticking straight out from the tip) produced "spectacular" images of the pentacene molecule. That's a well-studied type of hydrocarbon composed of five benzene rings interlocked in a row (C22H14).

Science / IBM
Several pentacene molecules are imaged using non-contact atomic force microscopy.


The benzene rings showed up brightly in the atomic-scale images, just as predicted by theory. One of the images published in Science even showed several of the five-ring molecules scattered around a surface like nano-caterpillars.

The researchers said their results were so good because the carbon monoxide molecule could get incredibly close to the pentacene molecule without picking it up or moving it around. When they tried probes that were tipped in metals, such as gold or silver or copper, the pentacene molecule would move around before the tip came close enough to map the chemical forces holding the molecule together.

The IBM team concluded that non-contact atomic force microscopy can be a great way to see how molecules are put together, but only if the microscope's probe is tipped with the right stuff.

The next step is to probe differently constructed molecules to see how they react with various types of tips - and see which kinds of surfaces work best as a molecular-scale lab bench. The goal of all this is to devise a molecular construction toolkit, as well as methods for watching how the tools in the kit work together.

"Eventually we want to investigate using molecules for molecular electronics," Gross told Chemistry World. "We want to use molecules as wires or logic switches or elements."

Experts in nanotechnology have long dreamed of creating molecular-scale circuitry that could revolutionize the computer world. But Gross told EETimes that the revolution is still far off. "It will take at least 15 years to see molecular electronic applications," he said, "and it is by no means certain that we will succeed."

That sounds like a refreshingly realistic assessment to me - but what do you think? Feel free to add your comments below.

Update for 10 p.m. ET Aug. 31: I've added a link to the video from NBC's "Nightly News" in which anchor Brian Williams discusses the magnificent molecule imagery.


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