An international team led by Empa and ETH researchers is "playing" with 3D building blocks on the nanoscale that are up to 100 times larger than atoms and ions. And although completely different, much weaker forces act between these nano "Lego bricks" than those that hold atoms and ions together, they form crystals all by themselves whose structures resemble natural minerals.
Cube-shaped nanocrystals, such as colloidal caesium lead halide perovskite nanocrystals, have been regarded as some of the brightest light emitters yet developed since they were first produced by the same research team around six years ago. In particular, they exhibit superfluorescence, which means they emit light collectively and much faster than the same nanocrystals can do in their conventional state, as a liquid or as a powder.
These highly ordered structures are created solely by the force of entropy, i.e. nature's eternal endeavor to create maximum disorder. This paradoxical behaviour comes about because, during crystal formation, the particles tend to use the space around them as efficiently as possible to maximize their freedom of movement in the late stages of solvent evaporation, just before they become "fixed" in their later crystal lattice position. These new megacrystals or superlattices exhibit unique properties and could herald a new era in materials science.
