Nano cubes bring better shaped crystals

Scientists in the United States have developed a new way to control the shape of metallic nanocrystals by using a small element of another metal as a ' seed ' and changing the conditions in reaction processes.

Peidong Yang and colleagues at the University of California at Berkeley started with the platinum nano (platinum) to create Paladium nanocrystals with three different shapes. The researchers say this technique can be applied in catalysis.

Morphology of nanocrystals is important because many of their physical and chemical properties depend on the shape. Much of the current research focuses on hetero-structure to create chalcogenide surfaces, while controlling the shape of metal nanoparticles with two separate components has not been studied much.

Yang and colleagues used cubic platin (Pt) nanocrystals with polished surfaces as 'seed' sprouts to directly develop a palladium compound (Pd) with lattice suitability . Platinum cubes are arranged approximately 130 nm on each side and only surface planes (100). Pd is forced to develop the same shape on the surface of these seeds and form a nuclear structure - Pt / Pd bimetallic casing.

Human structure - Pt / Pd casing developed in nitrous oxide environments with different concentrations (Photo: VatlyVietNam)

Depending on the reaction environment containing nitrous oxide, the team received three different shapes - cubic , cubic octahedral and octahedral block with different forms of the surface. Surface plane (100) for cubic shapes, (111) for octahedral blocks and planes for cube octahedral blocks. Scientists have received these structures when using electron microscopy (see picture). They say the amount of nitrous oxide in the reaction system is responsible for the final shape of nanocrystals because they control the velocity of forming Pd along the directions and theirs.

In contrast, when no ' germ ' is used, no shape control is seen and that is just a mixture of large elements including non-polyhedron elements, Rod shape and many elements are different. According to the team, this means that the Pt ' germ ' blocks' perform two tasks: it is to ensure a good surface for the development of the second metal on it and to control the shape. final of human hetero structure - casing.

"Shape control like this allows the production of nanocrystals with different shapes and types of surfaces," Yang told nanotechweb.org. 'So that can help catalytic reactions have many choices.'

The researchers say their technique could be applied to other materials such as ruthenium, iron - platinum and cobalt - platinum. In addition, these new hetero structures can also be used for catalysis such as magnetic and optical applications where shape control plays an extremely important role.

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