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NANOPARTICLES AND CLUSTERS

 

One of the key requirements for nanotechnology to become reality is the availability of powerful methods for the preparation of nanostructures at surfaces with dimensions of 10 nm and below. Since conventional top-down techniques like e-beam lithography are approaching their limitations on that length scale, completely different approaches are currently developed relying on the self-organization of larger molecules used as building blocks for the resulting nanostructures (bottom-up approaches). Ideally, such a bottom-up technique should allow - in a sequence of parallel processes - the in-situ deposition of ensembles of clean nanostructures of any kind of material with adjustable particle size and interparticle spacing.
One powerful variant of bottom-up approaches exploits the self-organization of diblock copolymers into micellar structures (when dissolved in an appropriate solvent like toluene) thereby allowing to use their cores as nanoreactors for the loading of an appropriate metal salt. In a second step, the loaded micelles are deposited onto a smooth substrate by dip-coating, where they form a hexagonally ordered array due to their spherical shape. The polymer matrix is then removed by means of an appropriate plasma resulting in an array of well-separated, clean metal nanoparticles of uniform size (1-10nm) which is controlled by adjusting the concentration of the metal salt within the micellar solution. In addition, the interparticle spacing (20-150nm) can be controlled by adjusting the length of the diblock-copolymers used for the self-assembly of the micellar nanoreactors. This way, a perfect platform is available for the systematic study of all fundamental physical (structural, electronic, magnetic, optical, thermodynamical, …) and chemical (catalytic, reactivity, etc.) properties as function of particle size at the transition from solids to clusters.