Single-Nanoparticle Maps Pave the Way for Better, Safer Nanotechnology

A method that combines electron microscopy and optical microscopy to map individual nanoparticle responses in different situations and contexts could pave the way for better nanomaterials and safer nanotechnology.

Researchers at Chalmers University of Technology in Sweden and the Technical University of Denmark developed the method and have discovered why different polycrystalline nanoparticles behave so distinctly when combined with hydrogen.

Maps of individual nanoparticles. The eight images show eight different nanoparticles of the same substance, palladium. Each nanoparticle consists of a number of grains, which are displayed as different colored fields on the images. The properties and response patterns of the various grains differ, and these in turn determine the properties and responses of the nanoparticles when they come into contact with other substances. Courtesy of Svetlana Alekseeva / Chalmers University of Technology.

"Our experiments clearly showed how the reaction with hydrogen depends on the specifics of the way in which the nanoparticles are constructed,” said Svetlana Alekseeva, a Postdoc at the Department of Physics at Chalmers University of Technology.“ It was surprising to see how strong the correlation was between properties and response - and how well it could be predicted theoretically.”

A nanoparticle of a certain material is made up of a number of smaller grains or crystals. The number of grains and how they are arranged is crucial in determining how the particle reacts in a certain situation or with a certain substance.

Alekseeva and her team produced maps — virtual portraits — of individual palladium nanoparticles. The images show the grains as a number of fields which are combined into a map. Some particles consist of a large number of grains, others have fewer grains, and the fields border on one another in different ways.

Using a combination of electron and optical microscopy, the researchers examined the grains and were able to monitor their response when they encountered other substances. This method made it possible for the researchers to map the basic material properties of nanoparticles at an individual level, and see how they correlate with the response of the particles when they interact with their environment.

The researchers say than their method opens up an almost infinite range of possibilities for further research and for the development of products and nanomaterials which are both technically optimized and safer from an environmental and health perspective.

"Nanotechnology is developing fast in the world, but so far the research into nanosafety is not happening at the same pace,” said says Christoph Langhammer, associate professor at the Department of Physics at Chalmers. “We therefore need to get a much better grasp of the risks and what distinguishes a hazardous nanoparticle from a non-hazardous one.”

The nanoparticles that have been investigated also operate as sensors in themselves. When they are illuminated, they reveal how they react with other substances, such as various gases or fluids.

The research has been published in the journal Nature Communications (doi:10.1038/s41467-017-00879-9).