Self-assembled Nafion films of varying thickness were generated on SiO2 terminated silicon wafer by immersion in Nafion dispersions of different concentrations. The impact of solvent/dispersion media was probed by preparing films from two different types of Nafion dispersionsIPA-diluted dispersion and Nafion-in-water dispersion. The thickness of films was ascertained by three different techniques: variable angle spectroscopic ellipsometry (VASE), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The three techniques yielded consistent nominal thicknesses of 4, 10, 30, 55, 75, 110, 160, and 300 nm for films self-assembled from IPA-diluted Nafion dispersions of concentrations 0.1, 0.25, 0.5, 1.0, 1.5, 2.0, 3.0, and 5.0 wt %, respectively. Films generated from 0.25–5.0 wt % Nafion-in-water dispersions generated comparable thicknesses. An interesting finding of our work is the observation of bimodal surface wettability, investigated by water contact angle. The sub-55 nm films were found to exhibit hydrophilic surface whereas the thicker films showed hydrophobic surface similar to those reported for Nafion membranes. Employing XDLVO theory, surface energies of the hydrophobic, 160 nm film was found to be similar to that reported for Nafion membrane whereas those for the hydrophilic 4 nm film yielded high electron-accepting/proton-donating parameters resulting in an enhanced surface polarity. It can be concluded that the structure and properties of the ultrathin (<55 nm) Nafion films are distinct from those of the thicker (but still submicrometer) films, which are likely similar to those of the well-studied Nafion membranes. No significant effect of dispersion type was observed for 10–300 nm thick films.

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A model system of alumina-supported vanadia particles, representing catalysts of the type oxide 1 /oxide 2 , was prepared under ultrahigh vacuum (UHV) conditions and characterized regarding its structural and electronic properties. As supporting oxide we used a thin, well-ordered alumina film grown on NiAl(110), which allows the application of scanning tunneling microscopy (STM), infrared reflection-absorption spectroscopy (IRAS), and X-ray photoelectron spectroscopy (XPS) without charging effects. Vanadium oxide particles were prepared via metal evaporation in an oxygen ambient, leading to the growth of small, roundish oxide particles with vanadium in the +3 oxidation state. The particles are shown to interact strongly with the alumina support, resulting in an increased alumina film thickness and a distortion of the alumina film structure. IR absorption signals of the deposits could be successfully assigned to specific V-containing species, thus providing insight into the inner structure of the particles. The species identified are surface-localized vanadyl groups (VdO), interface-localized vibrations involving V, O, and Al ions, and lattice structures typical of bulk V 2 O 3 .

Ultrathin crystalline silica layers grown on a Mo͑112͒ substrate have been shown to be a useful silica model oxide support in surface science model catalyst studies. As the oxide support material plays an important role in the catalytic process, a multitechnique surface science study is presented to characterize the morphological and electronic properties of the heteroepitaxial system SiO 2 /Mo(112). The long-range order of the silica epilayer which grows commensurate with a c(2ϫ2) surface unit mesh on the Mo͑112͒ substrate is studied by low-energy electron diffraction ͑LEED͒. The defect structure of the silica epilayer is characterized in a spot profile analysis ͑SPA͒-LEED study. Antiphase domain boundaries split the silica epilayer into an array of silica crystal grains whose average size and shape is determined. Aiming to prepare flat silica surfaces, the change in the surface roughness with progress in the film preparation is monitored in a combined SPA-LEED and scanning tunneling microscopy ͑STM͒ study and seen to influence also the Si-O stretching frequency in the infrared-reflection-absorption spectroscopy spectra. In STM images of the final silica film an average surface roughness of about 1 Å is detected. It is possible to visualize the silica film unit cell periodicity. A combined anger electron spectroscopy and ultraviolet photoelectron spectroscopy valence band study confirms the silica film stoichiometry and the growth of a 4:2 coordinated silica polymorph on the Mo͑112͒ surface. These various surface science studies allow us to propose models for the growth and structure of the silica epilayer on the Mo͑112͒ surface.

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