Scientists in Russian Academy of Sciences, Moscow have revealed a variety of transformations taking place on carbon surface under the influence of metal nanoparticles and microwaves.
Graphene "cut and paste" with metal nanoparticles was carried out under microwave irradiation. The study revealed unique processes occurring on the carbon layers under the influence of metal nanoparticles heated by microwave irradiation. Understanding the processes taking place in Metal/Carbon systems is crucial for development of new generation of highly efficient catalysts for organic synthesis and chemical industry. The authors described the key transformations responsible for catalyst evolution in connection with preparation of nanostructured Metal/Carbon systems.
The study, carried out in the laboratory of Prof. V.P.Ananikov at Zelinsky Institute of Organic Chemistry of Russian Academy of Sciences, discovered a variety of processes occurring on the surface of carbon material upon a contact with hot metal nanoparticles. Metal nanoparticles, heated by microwave radiation, caused significant morphological changes of the carbon surface: formation of patterns of pits and channels, penetration inside the carbon material and direct growth of carbon nanotubes.
As it is widely accepted now, discovery and systematic study of carbon nanotubes was one of the prominent groundbreaking points at the beginning of nanotechnology era. Carbon nanotubes are nanoscale tubular structures consisting of carbon atoms arranged in the interconnected six-membered rings within a cylindrical wall. From a certain point of view carbon nanotube may be represented as a graphene sheet (flat sheet of monoatomic thickness) rolled into a cylinder and carbon-glued at the edges. Direct access to carbon nanotubes starting from graphene (and especially starting from much cheaper precursor -- graphene layers in graphite) would be an outstanding process of great practical interest. The questions appear: how easy is to cut graphite sheets and to roll them up? Does it violate thermodynamic factors?
The present study, published in the ACS Catalysis journal, discovered a series of processes mediated in metal-carbon systems under microwave irradiation. "Cutting" of carbon slices by hot metal particles was clearly observed by field-emission scanning electron microscopy (FE-SEM). "Pasting" of carbon atoms into a new location has resulted in a growth of carbon nanotubes on the surface of graphite -- the process was also observed in the experiment under an inert atmosphere.
In the theoretical modeling the authors considered the following possibility: at the first stages graphene sheet can be cut into nanoribbons of one aromatic ring wide. Then, each nanoribbon is rolled into cycloparaphenylenes -- these molecules are known and were described previously. On the later stages, cycloparaphenylene rings are joined together to form the nanotube. Important stages of this process were modeled by quantum chemical calculations involving density functional theory.
Materials provided by Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences. Note: Content may be edited for style and length.
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