The reactivity of nanoscale systems are mainly dominated by quantum-size effects that govern the electronic spectra of clusters, by the structural dynamical fluxionality of clusters, as well as by impurity-doping effects. In this talk these fundamental and unique cluster properties are illustrated by specific examples obtained from mol. beam expts. in the gas phase and expts. on size-selected clusters on surfaces. Where possible, concepts for their understanding are given. Specifically, the nanoscale reactivity of free, small metal clusters will be presented. It will be shown how the interaction and chem. reactivity can be changed with cluster size. On a specific example it will be shown how the reaction mechanism and the energetics of a catalytic cycle can be extd. from the measured, temp.-dependent kinetics. The exptl. results are then compared to extensive ab-initio calcns. In a second set of expts. metal atoms and small metal clusters are formed in the gas phase, size-selected and then deposited on thin oxide films grown on metal surfaces. Chem. reactions and catalytic properties on the obtained cluster-assembled materials are then investigated under UHV conditions by means of thermal desorption, IR spectroscopy and pulsed mol. beams. The oxidn. and polymn. reactions are strongly dependent on cluster size and on the cluster-support interaction, and not only the no. of product mols. per cluster is changed, but also the branching ratio of the certain reactions. In many cases the measured reactivities are different from the ones obtained for the corresponding bulk systems. By combining the obtained exptl. results with ab-initio calcns., a picture of the size-dependent behavior of cluster-assembled materials is now emerging. [on SciFinder(R)]     «

The reactivity of nanoscale systems are mainly dominated by quantum-size effects that govern the electronic spectra of clusters, by the structural dynamical fluxionality of clusters, as well as by impurity-doping effects. In this talk these fundamental and unique cluster properties are illustrated by specific examples obtained from mol. beam expts. in the gas phase and expts. on size-selected clusters on surfaces. Where possible, concepts for their understanding are given. Specifically, the nano...     »