Shape-controlled synthesis of multiply twinned nanostructures is an important area of study in nanoscience, motivated by
the desire to control the size, shape, and terminating facets of metal
nanoparticles for applications in catalysis and other technologies. Controlling both the size
and shape of solution-grown nanoparticles relies on an understanding
of how synthetic parameters alter nanoparticle structures during
synthesis. However, while nanoparticle populations at the end of synthesis can be studied with standard electron microscopy methods, transient
structures that appear during some synthetic routes are difficult to observe. This is because these structures are often polycrystalline, with complicated overlapping crystal grains when that are difficult to interpret from a two-dimensional image.

A STROBE team from UC Berkeley and LBNL collaborated to study the
prevalence of transient structures during growth of multiply twinned
particles while also employing atomic electron tomography to reveal the atomic-scale three-dimensional structure of a Pd nanoparticle undergoing a shape transition, from decahedron to icosahedron. By identifying over 20,000 atoms within the structure, then classifying them according to their local crystallographic environment, we observe a multiply twinned structure consistent with a simultaneous successive twinning from a decahedral to icosahedral structure.