German researchers use laser technology to transform plastic into nanodiamonds and successfully capture them.

German researchers have utilized powerful lasers to convert ordinary plastic into tiny diamonds, successfully capturing complete crystals. A team from the Dresden-Rossendorf Helmholtz Center (HZDR) and the University of Rostock demonstrated that these nanodiamonds can survive under extreme pressure and temperature conditions and safely return to ordinary environments. Each recovered particle averages 3 nanometers, or three billionths of a meter, and contains approximately 3,000 carbon atoms. This laser method can produce high-purity, small-sized products with closely matched particle sizes, which is unattainable with traditional production methods, including explosions.

Simulating Extreme Environmental Conditions

The work began by simulating the conditions inside Neptune and Uranus, where temperatures can reach thousands of degrees Celsius and pressures are millions of times that of Earth's atmosphere. Laser irradiation of plastic created conditions for carbon to form diamonds, although the team initially could only detect these crystals briefly. Dominik Kraus from HZDR's new Institute of High Energy Density Physics stated that the team expected nanodiamonds to form, but the speed of their formation surprised them.

The team recovered these diamonds at the Extreme Light Infrastructure (ELI) located south of Prague, a laser facility that combines very high pulse energy with high repetition rates. At its L4n-P3 site, the laser fires three times per minute at a 0.004-inch (100 micrometer) thick PET plastic film. Each pulse sends a shockwave through the film, compressing the plastic, forming nanodiamonds, and ejecting them into a collection cylinder. In the recovery experiments, the plastic was compressed to a pressure of about 100 gigapascals, equivalent to approximately 14.5 million pounds per square inch.

When the compression wave exits the sample into a vacuum, it propels the diamonds at speeds exceeding 22,000 miles per hour (10 kilometers per second), comparable to a meteorite impact. Capturing their integrity requires a very soft medium, so the team used a water-soluble ionic gel that works effectively in a vacuum. Each laser shot generates about 10 trillion diamonds, but collecting a few hundred micrograms of samples requires about 100 shots. This is sufficient for characterization analysis of the particles using the ELMI-MV electron microscope at the University of Rostock, which can resolve individual atoms.

Ben Heuser, the lead author from HZDR, stated that seeing the moment of purified diamond formation was "a special moment we have been striving for over many years."

Prospects for Nanodiamond Applications

Nanodiamonds are hard, stable, and heat-resistant, and have already been used in abrasives and polishing agents. Smaller, cleaner, and uniformly sized particles could expand their applications in medicine, materials, and energy, including quantum sensors and imaging contrast agents. Smaller diamonds provide a greater total surface area for the same amount of material, which could enhance their catalytic efficiency in processes like using sunlight to decompose carbon dioxide. Starting with plastic also makes it easier to dope diamonds with other elements, tailoring them for tasks such as improving MRI contrast agents.

The next target is BC8 carbon. Higher energy-efficient lasers from fusion research can fire strong pulses more frequently, making the process scalable. The researchers aim to reach the milligram range, comparable to traditional production. The team also hopes to use laser compression to create BC8, a form of carbon that has only been theoretically predicted to date. Its density is expected to exceed that of diamond, while being equally hard and less prone to brittleness. The conditions required to form BC8 do not exist on Earth, so researchers plan to conduct their first experiments at higher pressures in November.