Quasicrystals are extraordinary objects. Just like crystals, they consist of ordered patterns, but unlike crystals, these patterns don’t repeat. They have many technological applications, so the discovery of a new one is a big deal.
Researchers from Brown University have discovered a quasicrystal that self-assembles from a single type of nanoparticle. This is the first definitive observation of quasicrystalline superlattice formed by a single component. The discovery is reported in Science.
The single nanoparticle is shaped like a triangular-based pyramid, a tetrahedron, that can create structures with different properties depending on the relative orientation of these nanoparticles to each other. In the study, the team saw them assemble themselves in a way that is not allowed in regular crystals, making the researchers realize these were building something different.
“Single-component quasicrystal lattices have been predicted mathematically and in computer simulations, but hadn’t been demonstrated before this,” senior author Ou Chen, an assistant professor of chemistry at Brown, said in a statement. “It’s a fundamentally new type of quasicrystal, and we’ve been able to figure out the rules for making it, which will be useful in the continued study of quasicrystal structures.”
The team didn’t set out to study quasicrystals. Their work focused on bridging the gap between the nanoscale and macroscale by building superstructures made of nanoparticles. The team demonstrated an extremely complex superstructure from a solid substrate. They then decided to use a liquid substrate and discovered that the particles began to organize themselves in a quasicrystal lattice.
“When I realized the pattern I was seeing was a quasicrystal, I emailed Ou and said ‘I think I’ve found something super-great,’” said Yasutaka Nagaoka, a postdoctoral scholar in Chen’s lab and the lead author of the new paper. “It was really exciting.”
The nanoparticles assembled into 10-sided shapes (decagons) that had the ability to flex their edges when they started to connect. The final structure is made of decagons with different-sided shapes (from nine to five) filling in the gaps. The team think that many quasicrystals can be built with this flexible polygon tiling system.
Quasicrystals are used in the coating of frying pans as well as in anticorrosion treatments on surgical instruments. Discovering new ones could lead to important technological breakthroughs as well as new insights into chemistry, math, art, and design.