Lateral diffusion of three different dye molecules (terrylene and two perylene diimides) in 4 to 225 nm thin films of 8CB liquid crystals in the smectic-A phase has been investigated on a single molecule level. The influence of film thickness on tracer diffusion can be qualitatively modeled by a hydrodynamic approach. Molecular tracking experiments as well as fluorescence correlation (FCS) studies reveal the presence of diffusion dynamics which span a range of at least more than one order of magnitude in time, which is much larger than the reported anisotropic self-diffusion observed for 8CB bulk samples. We tentatively assign the heterogeneity to the formation of diffusion limiting domains on a micrometer scale within the 8CB films or at the interfaces.

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.

Alkyl monolayers covalently bound to silicon were prepared through the reaction between 1-alkene molecules and hydrogen-terminated Si. The surfaces were anodized in nanometer scale with a contact-mode atomic force microscope (AFM) by applying positive bias voltage to the surface with respect to a conducting cantilever under ambient conditions. Following the anodization, patterned areas were selectively modified by chemical etching and coating with different molecules. The alkyl monolayers showed high resistance against chemical etching and protected Si surfaces from oxidation. AFM lithography of monolayers on Si was found to be useful for nanofabrication of organic/inorganic interfaces based on the Si–C covalent bond.

We present a case study about inkjet printing as a tool for molecular patterning of silicon oxide surfaces with hydrophobic functionality, mediated by n-octadecyltrichlorosilane (OTS) molecules. In contrast to state-of-the-art techniques such as micro contact printing or chemical immersion with subsequent lithography processes, piezo drop-on-demand inkjet printing does not depend on physical masters, which allows an effective direct-write patterning of rigid or flexible substrates and enables short run-lengths of the individual pattern. In this paper, we used mesithylene-based OTS inks, jetted them in droplets of 10 pL on a silicon oxide surface, evaluated the water contact angle of the patterned areas and fitted the results with Cassie's law. For inks of 2.0 mM OTS concentration, we found that effective area coverages of 38% can be obtained. Our results hence show that contact times of the order of hundred milliseconds are sufficient to form a pattern of regions with OTS molecules adsorbed to the surface, representing at least a fragmented, inhomogeneous self-assembled OTS monolayer (OTS-SAM).