Physical and Chemical Properties of Size-selected Supported Nanostructures

Abstract

Nanomaterials as new building blocks for the 21st century are meanwhile widely used in technology due to their extraordinary properties which can significantly differ from those of their bulk counterparts. Thus, it is of high importance to establish new strategies for their controlled synthesis representing one of the key requirements to access and exploit their size-dependent properties. This work first focuses on the preparation of ordered arrays of size-selected nanoparticles taking advantage of the self-assembly of macromolecules. It is found that homopolymer molecules with appropriate ligands can be used as efficient nanocarriers to load diblock copolymer micelles with metal salts. By selecting a proper molecular length of the homopolymer, ordered arrays of salt-loaded spherical micelles can be obtained by dip coating, thereby serving as templates for the subsequent nanoparticle formation using plasma techniques. Compared to the conventional micellar method which involves the direct loading of micellar nanoreactors with metal precursors, our new approach leads to both, an improved size distribution of the nanoparticles as well as a better degree of order of the resulting particle array. Since gold nitride has been speculated to possibly serve as a cheap replacement of pure gold in semiconductor industry, the formation and thermal stability of gold nitride at the nanoscale has been explored in this work. When starting from pure gold nanoparticles prepared by the micellar technique, the formation of gold nitride can be observed upon exposure to a nitrogen plasma. Here, a remarkable high thermal stability of the compound is found which, however, forms only for sufficiently small particle sizes thereby giving evidence for a new size-dependent property of a nanomaterial. The specific behavior of nanoscaled matter is influenced not only by its size but also by its morphology. We demonstrate, that ordered arrays of hollow nanoparticles can be achieved with the micellar technique for a number of systems. In contrast to solid nanoparticles, this new type of nanostructure is expected to exhibit markedly different electronic properties due to an enhanced electron confinement and, thus, new properties and applications are expected to emerge in the future.