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New tribo-systems composed of green chemicals have been investigated. Compatibility of friction modifiers with DLC was evaluated by using SRV test machine. A Zn-free lubricant formulation showed a steady-state friction coefficient of 0.15 for steel/steel contact. Hydrogenated DLC coating showed similar tribological properties when slid against steel. Interestingly, this lubricant showed low friction coefficient of 0.02 for hydrogen-free amorphous DLC when slid against steel. A model friction modifier improved the running-in performance and reduced wear for hydrogen-free DLC, while it marginally increased steady-state friction coefficient up to 0.04. The importance of material–lubricant combination and lubrication model has been highlighted. Copyright © 2014 John Wiley & Sons, Ltd.

A. Bongiorno and co-workers unveil in article 1300106 in a joint experimental and computational study the structural secrets of multilayer graphene oxide obtained from epitaxial graphene on SiC. The ultra-thin films combine a large interlayer spacing, a moderate water content, and large-area graphene sheets presenting an inhomogeneous oxidation at the nanoscale.

Intrinsically germanium-69-labeled super-paramagnetic iron oxide nanoparticles are synthesized via a newly developed, fast and highly specific chelator-free approach. The biodistribution pattern and the feasibility of ⁶⁹Ge-SPION@PEG for in vivo dual-modality positron emission tomography/magnetic resonance (PET/MR) imaging and lymph-node mapping are investigated, which represents the first example of the successful utilization of a ⁶⁹Ge-based agent for PET/MR imaging.

A combination of surface energy-guided blade coating and inkjet printing is used to fabricate an all-printed high performance, high yield, and low variability organic thin film transistor (OTFT) array on a plastic substrate. Functional inks and printing processes were optimized to yield self-assembled homogenous thin films in every layer of the OTFT stack. Specifically, we investigated the effect of capillary number, semiconductor ink composition (small molecule-polymer ratio), and additive high boiling point solvent concentrations on film fidelity, pattern design, device performance and yields.

A closely interconnected network of MoP nanoparticles (MoP-CA2) with rich nano­pores, large specific surface area, and high conductivity can function as a highly active non-noble metal catalyst for electrochemically generating hydrogen from acidic water. The network exhibits nearly 100% Faradaic efficiency and needs overpotentials of 125 and 200 mV to attain current densities of 10 and 100 mA cm⁻², respectively. The catalytic activity is maintained for at least 24 h.

Homogeneous dispersion of ultrafine Pt nanoparticles on 3D architectures constructed of graphene and exfoliated graphitic carbon nitride results in hybrids with 3D porous structures, large surface area, high nitrogen content, and good electrical conductivity. This leads to excellent electrocatalytic activity, unusually high poison tolerance, and reliable stability for methanol oxidation, making them of interest as catalysts in direct methanol fuel cells.

“United we stand, divided we fall.”–Aesop.

Aggregation-induced emission (AIE) refers to a photophysical phenomenon shown by a group of luminogenic materials that are non-emissive when they are dissolved in good solvents as molecules but become highly luminescent when they are clustered in poor solvents or solid state as aggregates. In this Review we summarize the recent progresses made in the area of AIE research. We conduct mechanistic analyses of the AIE processes, unify the restriction of intramolecular motions (RIM) as the main cause for the AIE effects, and derive RIM-based molecular engineering strategies for the design of new AIE luminogens (AIEgens). Typical examples of the newly developed AIEgens and their high-tech applications as optoelectronic materials, chemical sensors and biomedical probes are presented and discussed.

“United we stand, divided we fall!” Aggregate formation changes non-emissive luminogens to efficient emitters – this process is referred to as aggregation-induced emission (AIE). The AIE effect is caused by the restriction of intramolecular motions of luminogens in aggregate state. The AIE materials have found a wide variety of high-tech applications in the areas of optoelectronics, chemosensors, and biomedical probes.

Transparent electronic devices demonstrated by K. C. Choi, B.-K. Ju, and co-workers show as invisible to the eyes. In order to achieve stable device operatiom, the negative-bias illumination stressinduced instability must be improved. To achieving this, plasmonic filters engraved by laser interference lithography are integrated with amorphous oxide-semiconductor thin film transistors. The cut-off wavelength of plasmonic filters can be designed by controlling the periodic nanopatterns, and cutting off the light, which can affect amorphous oxide semiconductors, thereby realizing the photostable transparent electronic devices.

Enhancing the device performance of single crystal organic field effect transistors (OFETs) requires both optimized engineering of efficient injection of the carriers through the contact and improvement of the dielectric interface for reduction of traps and scattering centers. Since the accumulation and flow of charge carriers in operating organic FETs takes place in the first few layers of the semiconductor next to the dielectric, the mobility can be easily degraded by surface roughness, charge traps, and foreign molecules at the interface. Here, a novel structure for high-performance rubrene OFETs is demonstrated that uses graphene and hexagonal boron nitride (hBN) as the contacting electrodes and gate dielectric layer, respectively. These hetero-stacked OFETs are fabricated by lithography-free dry-transfer method that allows the transfer of graphene and hBN on top of an organic single crystal, forming atomically sharp interfaces and efficient charge carrier-injection electrodes without damage or contamination. The resulting heterostructured OFETs exhibit both high mobility and low operating gate voltage, opening up new strategy to make high-performance OFETs and great potential for flexible electronics.

Organic field effect transistors (OFETs) based on 2D graphene and hexagonal boron nitride heterostructures are fabricated by a dry-transfer method. The resulting heterostructured OFETs exhibit both high mobility and low operating voltage due to the atomically sharp interfaces of hBN flake and efficient charge carrier-injection from graphene electrodes.

Top-down e-beam lithography is combined with bottom-up bioinspired crystal growth by R. de la Rica, M. M. Stevens, and co-workers to grow nanoparticle clusters of controlled dimensions at desired locations on a chip. On page 3692, the key enabling factor to recreate biomineralization conditions is the patterning of enzyme nanoreactors as lines separated by nanometric distances such that the gradient of crystallization precursors generated by the enzymes is affected by the nanoscale organization of biocatalysts. Image Credit: Miguel Spuch-Calvar.

Capacitive deionization (CDI) is a competent water desalination technique offering an appropriate route to obtain clean water. On page 3917, Y.-M. Yan, K.-N. Sun and co-workers design and prepare a 3D-structured, graphene-based electrode using sponge (polyurethane, PU) as a template. The electrode possesses a large surface area, wide pore size distribution from nanopores to micropores, and low internal resistance, therefore exhibiting a remarkable electrosorptive capacity of 4.95 mg g⁻¹ and a desorption rate of 25 min.

The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox-liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfide, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS₂ sonicated with the antioxidant sodium bisulfite, results from Raman spectroscopy, X-ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS₂, upon thermal treatment up to 900 °C. The addition of the ionic antioxidant decreased dispersion stability in non-polar solvent, suggesting decreased compatibility with non-polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium–ion capacitors, and chemical sensing.

Restacked, layered compounds of graphite, molybdenum disulfide, and boron nitride are ideal materials for electronic devices, censors, and reinforced materials. A high-yielding process using sonochemical fragmentation of precursor powders with antioxidants is performed to generate modified restacked materials. The restacked powders demonstrate unique chemical, thermal, dispersive, and electrical properties that are desirable for polymer composites and other hybrid materials.

Henry's constants for hydrous ethanol, iso-octane and gasoline absorption in engine lubricants were determined using gas chromatography. Samples of synthetic SAE 5 W30, synthetic SAE 5 W40, semi-synthetic SAE 15 W40, mineral SAE 15 W40 and mineral SAE 25 W60 oil were used in the experiments. For all lubricants tested, typical molecular weights were considered, ranging from 500 to 5000 kg/kmol. The results show that, for any lubricant, Henry's constant for hydrous ethanol is about 2.2 times higher than that of gasoline, and about 4.3 times higher than that of iso-octane. Decreasing Henry's constant was observed with increasing lubricant molecular weight, regardless of the fuel type. Copyright © 2014 John Wiley & Sons, Ltd.

A novel semiconductor–metal–graphene stack design, which reduces interfacial defect density as well as provides channels for charge transport, has been demonstrated to harness the charge flow for efficient electron–hole separation. As a direct outcome, the designed hybrid structures exhibit significantly improved performance in photocatalytic hydrogen production from water.

Colloidal nanocrystals electronic energy levels are determined by strong size-dependent quantum confinement. Understanding the configuration of the energy levels of nanocrystal superlattices is vital in order to use them in heterostructures with other materials. A powerful method is reported to determine the energy levels of PbS nanocrystal assemblies by combining the utilization of electric-double-layer-gated transistors and advanced ab-initio theory.

In this work heteroepitaxial stabilization with nanoscale control of the magnetic Co₂FeO₄ phase at 250 °C is reported. Ultrasmooth and pure Co₂FeO₄ thin films (5–25 nm) with no phase segregation are obtained on perovskite SrTiO₃ single crystal (100) and (110) oriented substrates by atomic layer deposition (ALD). High resolution structural and chemical analyses confirm the formation of the Co-rich spinel metastable phase. The magneto-crystalline anisotropy of the Co₂FeO₄ phase is not modified by stress anisotropy because the films are fully relaxed. Additionally, high coervice fields, 15 kOe, and high saturation of magnetization, 3.3 μ_B per formula unit (at 10 K), are preserved down to 10 nm. Therefore, the properties of the ALD-Co₂FeO₄ films offer many possibilities for future applications in sensors, actuators, microelectronics, and spintronics. In addition, these results are promising for the use of ALD compared to the existing thin-film deposition techniques to stabilize epitaxial multicomponent materials with nanoscale control on a wide variety of substrates for which the processing temperature is a major drawback.

Stabilization with nanoscale control of the magnetic spinel ferrite Co₂FeO₄ phase is induced by heteroepitaxial growth at 250 °C using atomic layer deposition. This low cost and scalable thin film deposition technique opens a fascinating opportunity to develop and stabilize a large variety of materials with new properties without jeopardizing the system stability.

Silicene is a two-dimensional structure composed of a buckled hexagonal honeycomb lattice of silicon atoms. Freestanding silicene is yet to be synthesized, but epitaxial silicene monolayers have been directly observed or predicted to exist on a number of supporting substrates. Herein the atomic and electronic structures of five distinct epitaxial silicene morphologies on Ag(111) are examined through the complementary techniques of density functional theory and soft X-ray spectroscopy at the Si L_2,3 edge. Hybridization with the Ag(111) substrate is shown to cause these silicene monolayers to become strongly metallic, and the specific electronic interactions that are responsible for this metallic nature are determined. The results imply that epitaxial silicene on Ag(111) does not possess the Dirac cone electronic structure that is characteristic of freestanding silicene and graphene sheets.

The electronic structure of epitaxial silicene monolayers on Ag(111) is explored through the complementary techniques of density functional theory (DFT) calculations and synchrotron-based soft X-ray spectroscopy experiments. Interaction with the underlying Ag substrate is found to confer a metallic nature upon the silicene monolayers, ruling them out as possible Dirac cone hosts.

Graphene has attracted significant interest both for exploring fundamental science and for a wide range of technological applications. Chemical vapor deposition (CVD) is currently the only working approach to grow graphene at wafer scale, which is required for industrial applications. Unfortunately, CVD graphene is intrinsically polycrystalline, with pristine graphene grains stitched together by disordered grain boundaries, which can be either a blessing or a curse. On the one hand, grain boundaries are expected to degrade the electrical and mechanical properties of polycrystalline graphene, rendering the material undesirable for many applications. On the other hand, they exhibit an increased chemical reactivity, suggesting their potential application to sensing or as templates for synthesis of one-dimensional materials. Therefore, it is important to gain a deeper understanding of the structure and properties of graphene grain boundaries. Here, we review experimental progress on identification and electrical and chemical characterization of graphene grain boundaries. We use numerical simulations and transport measurements to demonstrate that electrical properties and chemical modification of graphene grain boundaries are strongly correlated. This not only provides guidelines for the improvement of graphene devices, but also opens a new research area of engineering graphene grain boundaries for highly sensitive electro-biochemical devices.

By controlling the structures, distribution, and chemical functionalization of grain boundaries of graphene at the nanoscale, one can envision disruptive technologies and novel fields of research. In this review, we present fascinating opportunities offered by this versatile material, together with a description of its essential structural and electronic features.

A periodic array of silicon nanotubes is demonstrated as a light absorber in n-Si/poly(3,4-ethylenedioxythiophene) :polystyrene sulfonate (PEDOT:PSS) hybrid solar cells by G. Y. Jung, H. Lee, and co-workers on page 3445. Sunlight is captured efficiently within the nanotube array, allowing a better power conversion efficiency.