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Today, the most effective and suitable method to obtain molecular H2 is the extraction from mixtures where it is present, using gas‐sieving membranes. To this aim, the preparation and characterization of layered nano‐composites are described, made of alternated layers of positively charged Poly(Diallyl Dimethyl Ammonium chloride) (PDDA) and negatively charged graphene oxide (GO) nanosheets with high and tunable selectivity for H2 purification. The composites are assembled exploiting electrostatic interactions and the layer‐by‐layer technique; this study correlates permeance tests with changes in chemical composition and structure of the material using X‐rays Photoelectron Spectroscopy, X‐rays diffraction water contact angle, and surface zeta‐potential measurements. Thanks to its layered nature, the GO‐PDDA composite shows an excellent selectivity, allowing faster permeation of H2 as compared to CO2 and Argon. By transforming the GO to reduced GO, the porosity of the nanosheets can be further increased, in this way increasing the permeance of the material and its selectivity at the same time, thus allowing to overcome the Robeson limit, the technological upper boundary to the performance of actual membranes. [ABSTRACT FROM AUTHOR]

Water‐gated organic field‐effect transistors (WGOFETs) are relevant devices for use in the fields of biosensors and biosystems. However, real applications require very stringent performance in terms of electrochemical stability and charge mobility to the organic semiconductor in contact with an aqueous environment. Here, a comparative study of two small‐molecule electron‐transporting perylenediimide semiconductors, which differ only in the N‐substituents named PDIF‐CN2 and PDI8‐CN2 is reported. The two materials present similar solid‐state arrangements but, while the PDI8‐CN2 shows a more 3D growth modality and electron mobility independent of the semiconductor layer thickness (≈10−4 cm2 V−1 s−1), the PDIF‐CN2 has an almost‐2D growth modality and the mobility increases with the semiconductor film thickness, reaching a maximum value of ≈5 × 10−3 cm2 V−1 s−1 at 30 nm. Above this thickness, the PDIF‐CN2 switches to a more 3D growth modality, and the mobility drops by one order of magnitude. XRR analysis indicates that a PDIF‐CN2 film can be modeled as a dense layered structure in which each layer is decoupled from the others due to the presence of fluorocarbon‐chains. The availability of additional pathways for charge transport from buried layers and the 2D versus 3D growth can explain the mobility dependence on the film thickness. [ABSTRACT FROM AUTHOR]

As fabrication and positioning of micro- and nanocrystals grow in importance in a wide range technological applications, there is an increasing requirement for the development of a shared technological platform that is able to process materials from solutions on large areas. Here, the application of lithographically controlled wetting (LCW) for the manipulation and positioning of single crystals directly on devices is reported. In the LCW, a stamp, consisting of a metallic grid, is positioned in contact with a liquid thin film spread on a substrate; under these conditions, the capillary forces pin the solution to the stamp protrusions, thus splitting the continuous film in separated droplets or channels. As the solvent evaporates and the solution reaches the saturation, the solute precipitates onto the substrate within the menisci, giving rise to a structured thin film, in correspondence of the protrusion of the stamp. The possibility to achieve a patterning of crystals of conjugated molecules with a defined shape and with controlled size directly on device is demonstrated and pattern of crystals are investigated using polarized optical microscopy, atomic force microscopy, X-ray diffraction; they are also electrically characterized. [ABSTRACT FROM AUTHOR]

Charge transfer at organic‐organic heterojunctions is fundamental to several organic electronics devices, including light‐emitting diodes, photovoltaic cells, light‐emitting transistors, and ambipolar field‐effect transistors. Here, probe charge transfer (CT) processes during the formation of an organic‐organic heterojunction are probed by performing in situ real‐time electrical characterization during the growth of pentacene/C60 ambipolar transistors. N‐type C60 channel formation follows two different percolation pathways, one being associated to linear C60 structures growing along pentacene grain boundaries and the other to C60 island percolation. Upon n‐channel formation a shift of pentacene p‐type transfer characteristics is observed, which is attributed to CT across the heterojunction interface as a result of Fermi level alignment. The findings allow estimation of the energy of thermally accessible CT‐states and their mobility along the interface. Finally, a model is proposed that relates the amount of transferred charge to details in the bilayer morphology and layer thicknesses. The model relies on the capacitive coupling between C60 and pentacene in the accumulation layer, which is consistent with a single hole transport channel. [ABSTRACT FROM AUTHOR]

We report herein an efficient, fast, and simple synthesis of an imine-based covalent organic framework (COF) at room temperature (hereafter, RT-COF-1). RT-COF-1 shows a layered hexagonal structure exhibiting channels, is robust, and is porous to N2 and CO2. The room-temperature synthesis has enabled us to fabricate and position low-cost micro- and submicropatterns of RT-COF-1 on several surfaces, including solid SiO2 substrates and flexible acetate paper, by using lithographically controlled wetting and conventional ink-jet printing. [ABSTRACT FROM AUTHOR]

The introduction of side chains in π-conjugated molecules is a design strategy widely exploited to increase molecular solubility thus improving the processability, while directly influencing the self-assembly and consequently the electrical properties of thin films. Here, a multiscale structural analysis performed by X-ray diffraction, X-ray reflectivity, and atomic force microscopy on thin films of dicyanoperylene molecules decorated with either linear or branched side chains is reported. The substitution with asymmetric branched alkyl chains allows obtaining, upon thermal annealing, field-effect transistors with enhanced transport properties with respect to linear alkyl chains. Branched chains induce molecular disorder during the film growth from solution, effectively favouring 2D morphology. Post-deposition thermal annealing leads to a structural transition towards the bulk-phase for molecules with branched chains, still preserving the 2D morphology and allowing efficient charge transport between crystalline domains. Conversely, molecules with linear chains self-assemble into 3D islands exhibiting the bulk-phase structure. Upon thermal annealing, these 3D islands keep their size constant and no major changes are observed in the organic field effect transistor characteristics. These findings demonstrate that the disorder generated by the asymmetric branched chains when the molecule is physisorbed in thin film can be instrumental for enhancing charge transport via thermal annealing. [ABSTRACT FROM AUTHOR]

The structure (size, shape, orientation) of CoPt alloy islands formed on NaCl(001) substrates was investigated using grazing-incidence small-angle X-ray scattering (GISAXS) combined with electron and X-ray diffraction and transmission electron microscopy. Co50Pt50 and Co25Pt75 islands formed at 473 K by co-deposition of Co and Pt species are oriented along the [001] direction, and their shapes are well described as truncated spheres with lateral sizes of around 4-5 nm. In contrast, using the same Co and Pt atomic fluxes, co-deposition at 673 K leads to the formation of strongly enriched Pt islands with larger sizes, and different orientations and shapes. The Pt enrichment is attributed to a large increase in the difference between the Co and Pt condensation coefficients with deposition temperature. Surprisingly, for the island assemblies formed at 673 K, the GISAXS patterns are dominated by the scattered intensities of the [001]- oriented islands with a truncated octahedron shape, thus masking the contributions of the [111]- and [110]-oriented islands which can exhibit larger sizes. [ABSTRACT FROM AUTHOR]

The morphology of epitaxial alloy nanostructures grown on a van der Waals-type WSe2(0001) surface was studied using grazing-incidence small-angle X-ray scattering (GISAXS). Assemblies of 111-oriented islands of (Co,Cr)Pt3 and (Co,Fe)Pt alloys were grown at different deposition temperatures, with nominal thicknesses from 0.1 to 3 nm, resulting in various island densities. Evaluation of the GISAXS patterns indicates that for similar growth conditions CrPt3 islands are flatter than CoPt or FePt islands and exhibit larger island volumes. These features are correlated with the better wetting behaviour and more negative formation enthalpy of the CrPt3 alloy. For dense arrays of self-assembled CoPt islands, much smaller island volumes are extracted from GISAXS experiments than are observed by scanning tunnelling microscope imaging, which indicates that only the upper parts of the islands contribute to the GISAXS signal. Another aspect that needs to be taken into account for interpreting GISAXS patterns is the sensitivity of GISAXS to facetting and thus its capacity to extract the island shape. The latter is strongly dependent on the island size. For islands with an average volume smaller than ∼20 nm3, the shape cannot be determined unequivocally. Furthermore, for dense island assemblies with some size dispersity, the identification of steep side-wall facets from the GISAXS patterns is not straightforward as observed for truncated tetrahedron-shaped CoPt3 islands. [ABSTRACT FROM AUTHOR]

Defects are inherent in transition metal dichalcogenides and significantly affect their chemical and physical properties. In this study, surface defect electrochemical nanopatterning is proposed as a promising method to tune in a controlled manner the electronic and functional properties of defective MoS₂ thin films. Using parallel electrochemical nanolithography, MoS₂ thin films are patterned, creating sulphur vacancy‐rich active zones alternated with defect‐free regions over a centimetre scale area, with sub‐micrometre spatial resolution. The patterned films display tailored optical and electronic properties due to the formation of sulphur vacancy‐rich areas. Moreover, the effectiveness of defect nanopatterning in tuning functional properties is demonstrated by studying the electrocatalytic activity for the hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

Many functional properties of organic semiconductors, such as charge transport, are regulated by structural order. The control of crystallinity, orientation, and positioning of crystals—the highest form of order—inside devices presents an extraordinary opportunity to fully exploit their potentialities. On page 2387, M. Cavallini and co‐workers demonstrate direct patterning of crystals of conjugated molecules onto devices, with defined shape and controlled size. [ABSTRACT FROM AUTHOR]