- Number 430 |
- January 12, 2015
“Atomic mismatch” creates nano “dumbbells”
This picture combines a transmission
electron microscope image of a
nanodumbbell with a gold domain oriented
in direction. The seed and gold domains in
the dumbbell in the image on the right are
identified by geometric phase analysis.
Image credit: Soon Gu Kwon.
Like snowflakes, nanoparticles come in a wide variety of shapes and sizes. The geometry of a nanoparticle is often as influential as its chemical makeup in determining how it behaves, from its catalytic properties to its potential as a semiconductor component.
Thanks to a new study from Argonne National Laboratory, researchers are closer to understanding the process by which nanoparticles made of more than one material – called heterostructured nanoparticles – form. This process, known as heterogeneous nucleation, is the same mechanism by which beads of condensation form on a windowpane.
Heterostructured nanoparticles can be used as catalysts and in advanced energy conversion and storage systems. Typically, these nanoparticles are created from tiny “seeds” of one material, on top of which another material is grown. In this study, the Argonne researchers noticed that the differences in the atomic arrangements of the two materials have a big impact on the shape of the resulting nanoparticle.
“Before we started this experiment, it wasn’t entirely clear what’s happening at the interface when one material grows on another,” said nanoscientist Elena Shevchenko of Argonne Center for Nanoscale Materials, a DOE Office of Science user facility.
In this study, the researchers observed the formation of a nanoparticle consisting of platinum and gold. The researchers started with a platinum seed and grew gold around it. Initially, the gold covered the platinum seed’s surface uniformly, creating a type of nanoparticle known as “core-shell.” However, as more gold was deposited, it started to grow unevenly, creating a dumbbell-like structure.
Thanks to state-of-the-art X-ray analysis provided by Argonne’s Advanced Photon Source (APS), a DOE Office of Science user facility, the researchers identified the cause of the dumbbell formation as “lattice mismatch,” in which the spacing between the atoms in the two materials doesn’t align.[Jared Sagoff, 630.252.5549,
jsagoff@anl.gov]
