Ultima edizione | Archivio giornali | Archivio tematico | Archivio video

CNR: Alamanacco della Scienza

Archivio

N. 11 - 25 giu 2014
ISSN 2037-4801

International info   a cura di Cecilia Migali

Tecnologia

‘Artificial graphene‘ nanocrystal studied at the Esrf

Using X-rays at the Esrf, the team, led by Daniel Vanmaekelbergh from the University of Utrecht in the Netherlands observed the nanocrystals aligning and then bonding into a honeycomb structure similar to that of graphene with the exception that the building blocks forming the structure are not carbon atoms but much larger nanocrystals. The study is published in 'Science'.

The unique property of the honeycomb structure is that it allows the electrons to move through the material as if they have no mass, allowing them to travel with a remarkably high and constant speed of more than a million kilometres an hour. It is predicted that 'artificial graphene’ made of nanocrystals has similar electronic properties.

The prominent components inside the nanocrystal honeycomb structure are lead selenide and cadmium selenide semiconductor nanoparticles. The advantage of using nanocrystals as artificial atoms stems from the fact that their properties can be tuned by tailoring their size and composition. This adds a large degree of flexibility to the already impressive electronic properties of graphene.

Recent Esrf experiments shed light on how this novel material is being formed: "The trick that we played, is combining the tuneable properties of nanocrystals with the special effects taking place in a honeycomb structure", says Vanmaekelbergh. "This allows for the design of a material with truly unique properties".

"The question with regard to this artificial honeycomb was how the material is actually formed", explains PhD student Mark Boneschanscher from the University of Utrecht. "By combining a large number of different analysis techniques we could resolve the structure on both the atomic and nanometre scale”. By merging this information with the structure of the individual nanocrystals, scientists could predict the mechanism of attachment of the nanocrystals, giving a first indication of how the honeycomb structures are formed.

For a complete analysis of the structure it was important to relate the atomic structure to the nanoscale structure. High resolution electron microscopy images provided the researchers with detailed local scale information. For a large scale analysis, the researchers turned to beamline Id01 at the Esrf, where a combination of small-angle and wide-angle scattering showed how the atomic crystal structure was aligned with the nanoscale honeycomb periodicity.

As a next step in the research, the team will study the formation of the honeycomb supercrystal in situ on the liquid-air surface.

Per saperne di più: - www.esrf.eu/home/news/general/content-news/general/honeycomb-artificial-graphene-nanocrystal-structure-studied-at-the-esrf.html