Apr 12 2010
Nanoparticles are recognized as promising building blocks for future applications, however their fixation on surfaces or in a matrix is everything else than a simple task.
Now physicists observed that a double layer of spherical C60 carbon-molecules, called fullerenes, is an ideal substrate for these microscopic particles. Their results, recently published in 'Nature Nanotechnology', are an important step towards the application of tailor-made nanosystems.
The properties of nanoparticles often differ from those of a large piece made of the same material. By tuning the size and composition of the nanoparticles, one can 'tailor' their chemical, optical or magnetic properties, and obtain features different from any bulk material. But for an application of this potential in the fields of catalysis, magnetic storage technology or optoelectronics, one has to fix the nanoparticles on surfaces or in matrixes. During this process the interaction with the surface or matrix at the worst destroys the unique properties of the nanoparticles.
Therefore it is important to develop techniques for a 'gentle' yet secure fixation of nanoparticles. This was now achieved by a team of physicists from the TU Dortmund, the University of Freiburg and the Fraunhofer Institute for Mechanics of Materials IWM, who deposited the particles on a layer of spherical C60 carbon-molecules, called fullerenes, and investigated their properties.
They showed that a double layer of fullerenes on a metal surface is an ideal substrate for the fixation of nanoparticles. The size and shape of the particles stayed unchanged for days even at room temperature, which is 'hot' for nanoscale processes. On a single layer of fullerenes, however, the particles shrank fast and disappeared within a few hours. Using atomic simulations this was traced back to temporary contacts bridging the fullerene layer and transporting atoms from the nanoparticles to the supporting metal surface.
On the basis of these results it might be possible, for example, to control the contact between nanoparticles by thin films which can either be penetrated or stay isolating. The scientists therefore not only demonstrated how to fix nanoparticles on surfaces without destruction of their geometric structure, but in particular they characterized a decay process for nanoparticles by the penetration of nanoscopic barriers in detail. These findings improve significantly the understanding of nanoparticle stability, which is an important step towards the application of tailor-made nanosystems.
Source: http://www.fraunhofer.de