Laser light transformed plastic into tiny diamonds

A similar effect could cause diamonds to shower down within planets such as Neptune and Uranus

illustration of a laser passing through a plastic bottle with an inset showing tiny nanodiamonds that also connects to the interior of a planet

Starting from the type of plastic found in soda bottles, scientists created tiny nanodiamonds (illustrated in inset). Researchers zapped the plastic with laser light (green) and probed it with X-rays (pink). The result suggests diamonds may form within ice giant planets such as Uranus and Neptune (lower right).


With the zap of a laser, trash can literally become treasure. In a new experiment, physicists shined a laser at bits of PET. That’s the kind of plastic used in soda bottles. The laser blast squeezed the plastic to about a million times Earth’s atmospheric pressure. It also superheated the material. This harsh treatment transformed the plain-old PET into nanosized diamonds.

The new technique could be used to make tiny diamonds for advanced tech based on quantum physics. That’s the branch of science that rules on small scales. Such devices could include new quantum computers or sensors. What’s more, these lab results could offer insight into planetary ice giants, such as Neptune and Uranus. Those planets have similar temperatures, pressures and combinations of chemical elements as seen in this experiment. So, the results suggest that diamonds may rain down inside those planets.

Researchers shared this work September 2 in Science Advances.

Like other plastics, PET contains carbon. In plastics, that carbon is built into molecules that contain other elements, such as hydrogen. But extreme conditions can coax that carbon into the crystal structure that makes up diamond.

For their new study, researchers trained lasers on samples of PET. Each laser blast sent a shock wave through the material. This amped up the pressure and temperature within it. Probing the plastic afterward with bursts of X-rays showed that nanodiamonds had formed.

Past studies had created diamonds by squeezing compounds of hydrogen and carbon. PET contains not just hydrogen and carbon, but also oxygen. That makes it a better match to the makeup of ice giants such as Neptune and Uranus.

The oxygen seems to help diamonds form, says Dominik Kraus. This physicist works at the University of Rostock in Germany. He worked on the new research. “The oxygen sucks out the hydrogen,” he says. This leaves behind carbon to form diamond.

Nanodiamonds are often produced using explosives, Kraus says. That process is not easy to control. But the new laser technique could offer fine control over diamond-making. This could make forging diamonds for specific uses easier.

“The idea is quite cool. You take water bottle plastic; you zap it with a laser to make diamond,” says Marius Millot. He’s a physicist at Lawrence Livermore National Laboratory in California. He was did not taken part in the study.

It’s not clear how easily tiny diamonds could be mined from plastic pieces, Millot says. But, “it’s pretty neat to think about.”

Science News physics writer Emily Conover studied physics at the University of Chicago. She loves physics for its ability to reveal the secret rules about how stuff works, from tiny atoms to the vast cosmos.

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