Assembly and characterization of molecular films for energetics and electronics.

This thesis was focused on the preparation and on the characterization, of functional thin films for molecular electronics and energetics. In the first part of this work a nanoscale electrical investigation of molecular wires was discussed. Molecular wires were prepared as a self assembled array on gold by means of a bottom up approach that exploits the coordination of metal with terpyridine-based ligands. These molecular wires were characterized by using different techniques. The formation and growth of the molecular films has been demonstrated by ToF-SIMS, XPS and UV-Vis spectroscopy. Structural information was obtained from NEXAFS measurements, that demonstrated that wires grow vertically to the surface and that the orientation doesn t change during the growth. The electrical characterization was performed by using the conductive atomic force microscopy (C-AFM) technique, that allowed to determine the molecular conduction mechanisms of these systems. The second part of the work was focused on the development of methodologies for functionalization of oxide substrates, suitable for applications in the field of dye sensitized solar cells. The ZP methodology has been applied, and the amount of surface coverage as well as the stability of the formed layers has been studied by using a phosphonate derivative of rhodamine B. Then the ZP method was applied to the preparation of different systems of interest in solar energy conversion, including a self assembled bilayer on TiO2 made out a dendrimeric complex of Ru (II) (the sensitizer) and a polyoxometallate (the catalyst) that can act as an electrode for photo -induced water splitting. Finally, the general problem of obtaining molecular depth profiling of organic materials has been discussed. In particular, a SIMS method (NO-assisted cluster-SIMS) has been studied, that gives promising results in this direction. With the aim of studying the applicability of the method to polymer-based multilayers, well-controlled layered systems have been prepared by means of layer-by-layer polyelectrolyte deposition. C60-SIMS depth profiling of these systems highlighted the possibility of obtaining a good profile depends heavily on the order in which layers with different radiochemical behavior are deposited. The cluster-SIMS technique was applied to the study of a system of interest in molecular electronics. In particular the measured C60-SIMS profiles provided evidence of in-depth inhomogeneous distribution of oligothiophenes in binary blends formed by oligomers with different molecular weight.