Small palladium particles with mean diameters ranging from 1.4 to 5 nm have been prepared within a plasma polymer matrix from a vinyltrimethylsilane monomer. Electron dift'raction has shown a decrease of the Pd lattice parameter with decreasing size of palladium cluster. These experimental data are used to deduce the value of the surface stress coefficient f =6.0+0.9 N/m. A contraction of the lattice constant of small palladium particles with decreasing of cluster size, to our best knowledge, has not been reported in the literature up to now. The results suggest that the dilatation of the Pd lattice constant, often reported in the literature, can be explained in terms of incorporation of impurities like carbon, hydrogen, and oxygen, or pseudomorphism in the case of crystalline supports.

Mononuclear titanium oxide species in faujasites of different Si/Al ratios are prepared by reaction of dehydrated zeolites with TiCl4 at 100 °C. The analysis of UV−vis diffuse reflectance spectra in combination with Raman spectroscopy and X-ray diffraction reveals the presence of three different types of titanium oxide species in the faujasite structure exhibiting excitation energies for the charge transfer from the 2p orbitals of oxygen ligands to the 3d orbitals of Ti of around 36 000, 45 000 and 49 000 cm-1. A reliable evaluation of diffuse reflectance spectra requires the calculation of the Kubelka−Munk spectra from the absolute reflectance of the sample. The different titanium oxide types are proposed to result from monofunctional, bifunctional, and multifunctional bonding of TiCl4 to isolated or neighboring OH groups or to hydroxyl nests with coordination numbers ranging from four to six. The blue shifts in the UV−vis spectra of mononuclear titanium oxide species can be discriminated from those of quantum-sized titania particles.

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Thin films (1−200 nm) of the title compounds were prepared by vapor deposition on glass at a controlled temperature. Film growth was studied in situ by optical absorption spectroscopy and measurement of the electrical conductivity. Independent of substrate temperature, a layered growth was found for ultrathin films of F16PcZn. During further deposition, this was followed by island formation (Stranski−Krastanov). Island growth from the beginning of deposition (Volmer−Weber) was found for MePTCDI. Both growth modes were confirmed by atomic force microscopy (AFM). Substrate temperature had a clear influence on the crystal structure of F16PcZn. A structure consisting of parallel stacks of molecules is formed first under all conditions. At lower temperature, this growth continues including, however, an increasing portion of amorphous material, whereas a square lattice of molecules is formed at higher temperature. This was found to be the stable modification of F16PcZn since films deposited at lower temperature could be irreversibly transformed into this structure by annealing of the films. A reversible dependence of optical absorption spectra on temperature was found for the stable modification of both materials in the range from 78 to 450 K. Bands were found to narrow considerably at lower temperature, and shifts were observed that were characteristic for stronger intermolecular interaction which was very well- defined at lower temperature. A considerable mobility of molecules on the lattice site as well as between sites is indicated by the results of this study. The optical data are discussed in terms of an established model of transition dipole coupling.

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