Benzohexacene guide in accurate determination of field effect carrier mobilities in long acenes.

Oligoacenes are promising materials in the field of electronic devices since they exhibit high charge carrier mobility and more particularly as a semiconductor in thin film transistors. Herein, we investigate the field effect charge carrier mobility of benzohexacene, recently obtained by cheletropic decarbonylation at moderate temperature. Initially, high performance bottom contact organic thin-film transistors (OTFTs) were fabricated using tetracene to validate the fabrication process. For easier comparison, the geometries and channel sizes of the fabricated devices are the same for the two acenes. The charge transport in OTFTs being closely related to the organic thin film at the dielectric/organic semiconductor interface, the structural and morphological features of the thin films of both materials are therefore studied according to deposition conditions. Finally, by extracting relevant device parameters the benzohexacene based OTFT shows a four-probe contact-corrected hole mobility value of up to 0.2 cm2 V-1 s-1.

Spectroscopic characterization of the on-surface induced (cyclo)dehydrogenation of a N-heteroaromatic compound on noble metal surfaces.

New nanoarchitectures can be built from polycyclic aromatic hydrocarbons (PAHs) by exploiting the capability of some metal surfaces for inducing cyclodehydrogenation reactions. This bottom-up approach allows the formation of nanostructures with a different dimensionality from the same precursor as a consequence of the diffusion and coupling of the PAHs adsorbed on the surface. In this work we present a thorough study, by means of a combination of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure and scanning tunneling microscopy with first principle calculations of the structural and chemical transformations undergone by pyridyl-substituted dibenzo[5]helicene on three coinage surfaces, namely Cu(110), Cu(111) and Au(111). Upon annealing, on-surface chemical reactions are promoted affecting the adsorbate/substrate and the molecule/molecule interactions. This thermally induced process favours the transformation from diffusing isolated molecules to polymeric nanographene chains and finally to N-doped graphene.

[Physiological model of water and chlorine shifts in the lamb stomach following intake of sheep milk or milk substitutes]. / Ein physiologisches Modell der Wasser- und Chlorverschiebungen im Lämmermagen nach der Schafmilch- oder Milchaustauscheraufnahme

It has been found that the average concentration of hydrogen ions in the milk chyme formed in the abomasum of suckling lambs within a period of 1-3 hours after feeding is above a pH of 3.0, similar to that of calves (JANCARIK, 1961). Hence, the digestion of milk proteins in lambs must be expected to proceed mostly at a pH higher than that of pepsin digestion, that is to say, in most cases it will range between 3.0 and 5.0. pH titration curves were made of fresh untreated ewe's milk obtained from ewes of different breeds (Merino, Finnsheep, Romanowsheep) to calculate the amounts of water and chlorine which have to be secreted with the gastric acid to attain the pH level that is required for the digestion of proteins contained in 100 ml of ewe's milk. Similarly, calculations were made with regression equations (table 2) showing that the gastric secretion of water and chlorine as expressed by the percentage proportion of H2O and Cl in the blood was considerably higher in the young and especially the very young animals (figure 1). The susceptibility of young lambs is due to this fact. Moreover, attention is drawn to the interrelationship between the gastric digestion of proteins and general possibility of dehydration and loss of chlorine in cases of disturbed gastric secretion (e.g. gastric achlorhydria, absence of gastric enzymes, gastrogenic dysentery). The buffer capacity of fresh ewe's milk cannot be directly estimated from the concentration of hydrogen ions in it. It has been established that in some sheep the pH of milk may, under physiological conditions, exceed the value of 7.0; a condition that has an adverse effect on the nutrition of weak lambs. Figure 2 shows the differences between different breeds concerning gastric Cl secretion. The situation is similar with regard to H2O.