Regular arrays of Pd and PdAu clusters on ultrathin alumina films for reactivity studies.

Hexagonal arrays of Pd and PdAu clusters are produced by condensation of metal vapors under UHV on a nanostructured alumina ultrathin film at 320 K. The alumina presents a hexagonal network of point defects that are nucleation centers for Pd. The growth of the Pd clusters is uniform leading to a very narrow size distribution in the range of size of few atoms to about 400 atoms.

Long-range ordered nanodomains of grafted electroactive molecules.

We demonstrate the capability to build zero and one-dimensional electroactive molecular nanostructures ordered over a macroscopic scale and stable under ambient conditions. To realize these arrays, we use the selective grafting of functionalized thiols (juglon and terthiophene based) on a self-organized metallic template. The nanoscale patterning of the molecular conductance is demonstrated and analyzed by scanning tunneling spectroscopy.

Transition from molecule to solid state: reactivity of supported metal clusters.

The evolution of the adsorption energy of carbon monoxide (CO) molecules on palladium (Pd) clusters as function of Pd particle size from the molecular regime (less than ~100 atoms per particle) to the bulk regime has been revealed. This adsorption energy is retrieved from the residence time of CO molecules on the Pd clusters, measured by a pulsed molecular beam technique, versus temperature. Unprecedented accuracy on the determination of the particle size has been achieved here by using a regular array of metal clusters exhibiting a size dispersion down to the ultimate limit of a Poisson distribution.

Preparation of regular arrays of bimetallic clusters with independent control of size and chemical composition.

Regular arrays of bimetallic clusters have been prepared by atomic deposition, under UHV, on a nanostructured ultrathin alumina film. The alumina films are obtained by oxidation at 1000 K of a Ni3Al (111) surface. They present two regular hexagonal superstructures with lattice parameters of 2.