X-ray vision

While X-ray imaging is often thought of as a medical technology, applications for it have advanced enormously during the past 100 years of its use.

European scientists now says that a stronger type of X-ray could be used as a new non-destructive way to the detailed chemical composition of all kinds of objects, ranging from meteorites to fossils.

On Sunday, researchers working at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, published a paper in the journal Nature Materials describing a new way of rendering images of the chemical composition of samples by using particular types of X-rays.

That means the synchrotron facility - a circular construction with an 800-meter circumference - can be used to differentiate between graphite and diamond, for instance. Although both substances are pure carbon, they have completely different properties as the chemical bonds between the carbon atoms are different.

Simo Huotari a physics researcher at the University of Helsinki, is one of the scientists who discovered the technique. He says it came as a "lucky finding" while doing routine work on the ESRF facility's system of mirrors and X-ray detectors.

"When the X-ray beam was going through a sample, the X-ray mirror was taking an image of what the beam sees inside the sample, and was reflecting that image on the detector," he told Deutsche Welle. "We were suddenly able to start forming three-dimensional images."

Conventional X-ray images are created based on the amount of X-rays which pass through a particular mass. Dense bones absorb more X-rays than flesh does, making it possible to expose a contrasting image.

But the synchrotron radiation technique uses X-rays powerful enough to kill biological entities, which is why it is never used on biological samples. The synchrotron uses a system of curved mirrors and detectors to measure what scatters back from a sample, rather than what passes through it.

"If you have oxygen or you have carbon, the characteristic energy loss is completely different," Huotari said. "So after detecting the photon we can say whether it was deflected by an oxygen atom, or by a carbon atom."

Highly specialized equipment

Much of what the new synchrotron radiation technique is capable of could be done before, however, the difference is that now scientists no longer have to destroy a sample to peer at a sample's chemical makeup.

That means they could observe the chemical changes a functional lithium ion battery goes through as it is charged and discharged, for instance. Or, they could non-destructively study the chemical composition of valuable samples like meteors or fossils buried in rock.

"In a lithium battery, for example, the chemistry of lithium is exactly the important thing that you need to look at," Huotari said. "But so far there has been no technique to look at the chemistry of lithium. It's a very light material, and is nearly transparent to X-rays when it's embedded deep inside your operational battery."

Christian Schroer, a physics professor at the Dresden University of Technology, said the new technique can render chemical properties which could previously only be detected on surfaces or in very thin samples.

"We're now capable of really looking into objects, especially when samples are otherwise not very accessible," he told Deutsche Welle.

But Schroer added that despite its potential, the technique is highly specialized and therefore unlikely to be used in widespread research. There are only a handful of synchrotron radiation facilities in Europe, as he pointed out.

"In general you have to have a very special sample to use a synchrotron radiation facility," he said.

Visualizing a chemical environment

Christian Sternemann, a physics professor at the Dortmund University of Technology, said one of the major advantages of the new technique is that materials can be studied within complicated chemical surroundings.

"From my point of view I think it will have a major impact on research, because even for applications where you are looking for light elements, it's a unique technique," he told Deutsche Welle. "I think there will be impact especially if finer X-ray beams can be used which are highly focused, and if the intensity one is able to bring to a sample is optimized."

The University of Helsinki's Huotari also said a major advantage of the technique is its ability it gather information about the chemical surroundings of molecules.

"By fine-analysing the energy losses, we can also determine in what kind of chemical environment that atom was - what kind of molecule it was bound to, or what kind of crystal it was bound to," he added.

Author: Gerhard Schneibel
Editor: Cyrus Farivar