A cutaway illustration of a crystalline Au-core Ag-shell bimetallic nanoparticle. This particle has a core radius of 1.2 nm and the total particle diameter is 4 nm. The lattice spacing for both metals is approximately 4.08 Angstroms, so there is no lattice mismatch at the interface. Even though the particle is roughly spherical, it is easy to see that the exposed surfaces are different crystalline faces, and that a large fraction of the atoms are at or close to the surface of the particle.

Research by Chuck Vardeman. Image rendered by Matthew Meineke.