One of the main goals of molecular electronics is to achieve electronic functions from devices consisting of tailored organic molecules connecting two metal electrodes. The fabrication of nanometre-scale spaced electrodes still results in expensive, and often scarcely reproducible, devices. On the other hand, the 'conductance' of long organic molecules--generally dominated by the tunnelling mechanism--is very poor. Here, we show that by incorporating a large number of metal centres into rigid molecular backbones we can obtain very long (up to 40 nm) and highly 'conductive' molecular wires. The metal-centre molecular wires are assembled in situ on metal surfaces via a sequential stepwise coordination of metal ions by terpyridine-based ligands. They form highly ordered molecular films of elevated mechanical robustness. The electrical properties, characterized by a junction based on Hg electrodes, indicate that the 'conductance' of these metal-centre molecular wires does not decrease significantly even for very long molecular wires, and depends on the nature of the incorporated redox centre. The outstanding electrical and mechanical characteristics of these easy-to-assemble molecular systems open the door to a new generation of molecular wires, able to bridge large-gap electrodes, and to form robust films for organic electronics.

The performance of bottom‐contact thin‐film transistor (TFT) structures lags behind that of top‐contact structures owing to the far greater contact resistance. The major sources of the contact resistance in bottom‐contact TFTs are believed to reflect a combination of non‐optimal semiconductor growth morphology on the metallic contact surface and the limited available charge injection area versus top‐contact geometries. As a part of an effort to understand the sources of high charge injection barriers in n‐channel TFTs, the influence of thiol metal contact treatment on the molecular‐level structures of such interfaces is investigated using hexamethyldisilazane (HMDS)‐treated SiO2 gate dielectrics. The focus is on the self‐assembled monolayer (SAM) contact surface treatment methods for bottom‐contact TFTs based on two archetypical n‐type semiconductors, α,ω‐diperfluorohexylquarterthiophene (DFH‐4T) and N,N′bis(n‐octyl)‐dicyanoperylene‐3,4:9,10‐bis(dicarboximide) (PDI‐8CN2). TFT performance can be greatly enhanced, to the level of the top contact device performance in terms of mobility, on/off ratio, and contact resistance. To analyze the molecular‐level film structural changes arising from the contact surface treatment, surface morphologies are characterized by atomic force microscopy (AFM) and scanning tunneling microscopy (STM). The high‐resolution STM images show that the growth orientation of the semiconductor molecules at the gold/SAM/semiconductor interface preserves the molecular long axis orientation along the substrate normal. As a result, the film microstructure is well‐organized for charge transport in the interfacial region.

The dynamic adsorption of human serum albumin (HSA) and plasma fibronectin (Fn) onto hydrophobic poly-(hydroxymethylsiloxane) (PHMS) and the structures of adsorbed protein layers from single and binary protein solutions were studied. Spectroscopic ellipsometry (SE) and quartz crystal microbalance with dissipation monitoring (QCM-D) together with atomic force microscopy (AFM) were used to measure the effective mass, thickness, viscoelastic properties, and morphology of the adsorbed protein films. Adsorbed HSA formed a rigid, tightly bound monolayer of deformed protein, and Fn adsorption yielded a thick, very viscoelastic layer that was firmly bound to the substrate. The mixed protein layers obtained from the coadsorption of binary equimolecular HSA-Fn solutions were found to be almost exclusively dominated by Fn molecules. Further sequential adsorption experiments showed little evidence of HSA adsorbed onto the predeposited Fn layer (denoted as Fn . HSA), and Fn was not adsorbed onto predeposited HSA (HSA . Fn). The conformational arrangement of the adsorbed Fn was analyzed in terms of the relative availability of two Fn domains. In particular, 4 F 1 35 F 1 binding domains in the Hep I fragment, close to the amino terminal of Fn, were targeted using a polyclonal antifibronectin antibody (anti-Fn), and the RGD sequence in the 10th segment, in the central region of the molecule, was tested by cell culture experiments. The results suggested that coadsorption with HSA induced the Fn switch from an open conformation, with the amino terminal subunit oriented toward the solution, to a close conformation, with the Fn central region oriented toward the solution.

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The effect of coadsorption on the conformational arrangement of human plasma fibronectin (Fn) was studied for mixtures with human serum albumin (HSA) adsorbed onto mildly hydrophilic gold substrates. Quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) were used to measure the mass uptake, thickness, viscoelastic behaviour, and morphology of the adsorbed protein adlayers. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was employed to determine the composition of binary protein adlayers, taking advantage of the principal component analysis (PCA) technique of ToF-SIMS data. Thus, the ToF-SIMS results provided the particular fragmentation patterns of the two proteins, showing that the resulting mixed protein layers were predominantly formed by Fn molecules, even for binary solutions with high molar fraction of HSA. The conformational arrangement of the Fn molecules was studied by combining ToF-SIMS and QCM-D techniques. ToF-SIMS data allowed the identification of Type I-Type III modules of Fn and showed that pure Fn layers predominantly expose Type III modules, while coadsorbed Fn/ HSA layers predominantly expose Fn Type I epitopes. QCM-D was employed to measure the relative uptake of a polyclonal antibody (anti-Fn) to the 4 F 1 5 F 1 binding domain in the Fn Hep I fragment in Type I modules, showing that pure Fn adlayers have a reduced anti-Fn binding capacity, as expected for Type I modules buried within the adlayers, while coadsorbed Fn layers bind more efficiently the anti-Fn, as the concerned Type I module is predominantly exposed at the layer surface. The results overall demonstrated that coadsorption of Fn and HSA onto mildly hydrophilic gold substrates prompts Fn to undergo a closed-to-open conformational switch.