Argonne scientists watch the birth of nanoparticles for the first time

A team of scientists at the US Department of Energy's (DOE) Argonne National Laboratory and the Carnegie Institution of Washington has succeeded in "watching" nanoparticles grow in real time.

The revolutionary technique allows researchers to learn about the early stages of nanoparticle generation, long a mystery due to inadequate probing methods, and could lead to improved performance of the nanomaterials in applications including solar cells, sensing and more.

"Nanocrystal growth is the foundation of nanotechnology," said lead researcher Yugang Sun, an Argonne chemist. "Understanding it will allow scientists to more precisely tailor new and fascinating nanoparticle properties."

The way that nanoparticles look and behave depends on their architecture: size, shape, texture and surface chemistry. This, in turn, depends very much on the conditions under which they are grown.

"Accurately controlling nanoparticles is very difficult," Sun explained. "It's even harder to reproduce the same nanoparticles from batch to batch, because we still don't know all the conditions for the recipe. Temperature, pressure, humidity, impurities - they all affect growth, and we keep discovering more factors."

In order to understand how nanoparticles grow, the scientists needed to actually watch them in the act. The problem was that electron microscopy, the usual method for seeing down into the atomic level of nanoparticles, requires a vacuum. But many kinds of nanocrystals have to grow in a liquid medium - and the vacuum in an electron microscope makes this impossible. A special thin cell allows a tiny amount of liquid to be analyzed in an electron microscope, but it still limited the researchers to a liquid layer just 100 nanometers thick, which is significantly different from the real conditions for nanoparticle synthesis.