Complex crystals that mimic metals — including a structure for which there is no natural equivalent — can be achieved with a new approach to guiding nanoparticle self-assembly.

Rather than just nanoparticles that serve as «atom equivalents,» the crystals produced and interpreted by Northwestern University, University of Michigan and Argonne National Laboratory rely on even smaller particles that simulate electrons.

«We’ve learned something fundamental about the system for making new materials,» said Northwestern’s Chad Mirkin, the George B. Rathmann Professor of Chemistry in the Weinberg College of Arts and Sciences and a co-corresponding author of the paper in Nature Materials. «This strategy for breaking symmetry rewrites the rules for material design and synthesis.»

Nanoparticles have the potential to enable new materials with properties that can be carefully designed, but one of the big challenges is making these materials self-assemble. Nanoparticles are too small and numerous to build brick by brick.

Colloidal crystals are a family of self-assembled arrays made by nanoparticles, with potential applications in photonics. Crystals that can transform light may be engineered for everything from light sensors and lasers to communications and computing.

«Using large and small nanoparticles, where the smaller ones move around like electrons in a crystal of metal atoms, is a whole new approach to building complex colloidal crystal structures,» said Sharon Glotzer, the Anthony C. Lembke Department Chair of Chemical Engineering at U-M and a co-corresponding author.

Story Source: Materials provided by University of Michigan. Note: Content may be edited for style and length.