Quantum dots, nanoparticles made out of a semiconductor material, emit photons when excited, which end up visible to the human eye as light. Because of that property, quantum dots are seen as the basis for the next generation of display technology. They’re also theorized to be the best avenue toward quantum computing, so the more we learn about quantum dots, the closer we move toward a quantum computer displaying information on a next generation monitor. Using molten metal salt, scientists at Rice University accidentally created a new form of quantum dot, proving lava might be an effective ingredient in creating a quantum computer.

The lava dots, as co-author of the study Michael Wong calls them, were accidentally created when Wong and his team at Rice University were looking for a cheaper way to produce tetrapods. Tetrapods are particles smaller than a living cell that are notable for being able to harvest sunlight for use in solar panels. The process to create tetrapods, Wong notes, was already cheap, but the team was looking for a way to cut costs further. They removed an ingredient from the tetrapod creation process — phosphorous surfactant — and it just so happened the result was hollow, ball-shaped, soft-shelled particles. Wong recalls it took the team over a year to understand exactly what happened, and how the tiny balls were created.

Sravani Gullapalli, Rice grad student, added selenium, cadmium nitrate, and some cetyl trimethylammonium bromide (CTAB) to an oil solvent, then heated and stirred the mixture. The cadmium nitrate melted and left behind tiny droplets that could not be seen without a microscope, but when the selenium melted, it formed around the cadmium nitrate droplet, and the droplet essentially melted away and left a hole in the middle of the melted selenium.

The lava dot measured in at around 15-20 nanometers wide, while a standard quantum dot measures in at around 2-10 nanometers wide. The lava dot’s doughnut-hole is around 4-5 nanometers in diameter.

Aside from creating a quantum dot from a new material, the important discovery is that the selenium doughnut is wrapped in a soft selenium shell, which easily compresses when close to other selenium doughnuts, keeping them from touching. This means a larger amount of dots can be packed into a tighter space. Recently, a team of chemists figured out a method to pack more dots onto a metal surface while keeping them from touching, preserving their state. Ideally, this method would lead to being able to store more information on a hard drive. Perhaps the technique — or at least, the idea — used to create the safe selenium coating could be applied to this method of increasing hard drive storage capacity.

Wong notes that the new hollow lava dots “met and even exceeded some performance metrics of quantum dots,” which, considering quantum dots are the basis of quantum computing and next-gen QLED displays, is a positive step toward those two goals.

Now read: Hard drives could use similarly-coated dots to increase storage capacity

Research paper: doi:10.1088/0957-4484/23/49/495605 – “Molten-droplet synthesis of composite CdSe hollow nanoparticles”

[Image credit: Geoff Mackley]