Dipole moment of nanoparticles at interfaces

The properties of heterogeneous interfaces are modified essentially by the presence of nanoparticles. We provide a model and give spectroscopic eviden ce that nanoscale clusters exist which have a metallic core and a shell of an almost perfect oxide. Such clusters produce a large dipole moment which manifests itself as shifts in core levels as seen by photoelectron spectros copy, as well as non-Ohmic rectifying behavior in the device electrical pro perties.