Highly Efficient Microscopic Charge Transport within Crystalline Domains in a Furan‐Flanked Diketopyrrolopyrrole‐Based Conjugated Copolymer

Elucidating the interrelation between the molecular structure and charge transport properties in conjugated polymer thin films is an essential issue in developing the design principle of high‐performance polymer materials for application in organic electronics. In particular, the backbone planarity is suggested to be a key element that governs the transport performance, especially in recently developed donor–acceptor (D–A)‐type copolymers exhibiting high mobility, whereas the direct evaluation of the intrinsic transport performance, usually realized only within the small crystalline domains, is difficult by using conventional macroscopic measurements. Here, it is demonstrated that a D–A type copolymer, PDPPF‐DTT, which consists of furan‐flanked diketopyrrolopyrrole (DPP) and dithienothiophene (DTT) units in the conjugated backbone, exhibits a highly efficient charge transport performance within the crystalline domains with a remarkably low activation energy of less than 8 meV, based on microscopic measurements using field‐induced electron spin resonance spectroscopy. This high transport performance is primarily caused by the high backbone planarity realized by introducing furan‐flanked DPP and fused dithienothiophene units, which is demonstrated from the density functional theory calculations. This result provides a microscopic indication of the effectiveness of the present molecular design to produce a planar backbone and realize highly efficient charge transport performance.     

Fracture behavior of wasted activated carbon powder composites

At the Waterworks Bureau (Tokyo Metropolitan Government), activated carbon has been used for filtering water. After being used for the filtering process, it is normally disposed or burned for thermal recycling. However, CO₂ emissions occur during the thermal recycling. This work focuses on the identification of mechanical behavior of recycled wasted activated carbon (WAC) in order to elaborate smart materials having mechanical–electrical functions. Acoustic emission technique (AE) was used intensively as characterization support in which sensors were attached to detect microdamage during bending tests. At first, the resonant frequencies of the specimens were measured using the through-transmission test. The resonant frequencies of the specimens containing low weight fractions of WAC powder were less in comparison to the frequencies of the specimens with higher volume fraction. The frequency analysis was carried out with the projected wavelet transform on the signals detected during bending tests. Obtained data showed that, typically, the first major peaks showed the resonant frequency of the sensors, while the second major peaks exhibited signals indicative of resin cracking. The surfaces of the fractured specimens were analyzed by optical microscopy in order to visualize the crack formation and propagation on the activated carbon composite under flexural stresses. Consequently, fractographic and AE analyses provide better understanding of the failure mechanisms involved.     

Synthesis of Large‐Area InSe Monolayers by Chemical Vapor Deposition

Recently, 2D materials of indium selenide (InSe) layers have attracted much attention from the scientific community due to their high mobility transport and fascinating physical properties. To date, reports on the synthesis of high‐quality and scalable InSe atomic films are limited. Here, a synthesis of InSe atomic layers by vapor phase selenization of In₂O₃ in a chemical vapor deposition (CVD) system, resulting in large‐area monolayer flakes or thin films, is reported. The atomic films are continuous and uniform over a large area of 1 × 1 cm², comprising of primarily InSe monolayers. Spectroscopic and microscopic measurements reveal the highly crystalline nature of the synthesized InSe monolayers. The ion‐gel‐gated field‐effect transistors based on CVD InSe monolayers exhibit n‐type channel behaviors, where the field effect electron mobility values can be up to ≈30 cm² V^?1 s^?1 along with an on/off current ratio, of >10⁴ at room temperature. In addition, the graphene can serve as a protection layer to prevent the oxidation between InSe and the ambient environment. Meanwhile, the synthesized InSe films can be transferred to arbitrary substrates, enabling the possibility of reassembly of various 2D materials into vertically stacked heterostructures, prompting research efforts to probe its characteristics and applications.     

Wind tunnel experiment for predicting a visible plume region from a wet cooling tower

We developed a new method for a wind tunnel experiment to predict a visible plume region from a wet cooling tower. The diffusion of water vapor and heat emitted from a cooling tower in a wind tunnel is estimated using a tracer gas. The instantaneous concentration of the tracer gas is measured using high-response flame ionization detectors. A moist plume-induced fog is assumed to be generated whenever the instantaneous specific humidity predicted from the concentration of the tracer gas at measured points is larger than the inferred saturation specific humidity. To confirm the validity of the present method, the results in the wind tunnel experiments are roughly compared with the observations obtained at the mechanical-draft cooling tower of the Benning Road plant. The results show that the visible plume length and height are nearly in agreement with observations and the present method has the capability to predict the visible plume region from the cooling tower.     

Analysis of precursors for crystal growth of YBaCuO thin films in magnetron sputtering deposition

We correlated the crystallinity of YBaCuO films prepared by magnetron sputtering deposition using Ar/O₂ mixture gas with the atomic and molecular composition in the gas phase. YBaCuO films were deposited on MgO substrates at 670 °C. Two-dimensional distributions of Y, Ba, Cu, YO, BaO, and CuO densities and one-dimensional distribution of O density were measured by laser-induced fluorescence spectroscopy. The Y and Ba densities decreased significantly with the increase of the O₂ partial pressure, and they were below the detection limit at an O₂ flow ratio of 10% and a total gas pressure of 53 Pa. The decrease in the Y and Ba densities was compensated by an increase in the YO and BaO densities. The decrease in the Cu density with the increase of the O₂ partial pressure was less significant, while the CuO density was below the detection limit at all the discharge conditions. The O density was evaluated to be 10¹²-10¹³ cm^− 3, which was much higher than the Cu density. On the other hand, YBaCuO films with high crystallinity were obtained at total gas pressures of 53-80 Pa and O₂ flow ratios of 50-70%. Therefore, it is concluded that the precursors for the deposition of YBaCuO films with high crystallinity are Cu, YO, BaO, and O.     

A Novel (2,2‐Diarylvinyl)phosphine/Palladium Catalyst for Effective Aromatic Amination

A new series of diarylvinylphosphine ligands was designed and synthesized. A catalyst system, consisting of the ligands and palladium species, effectively catalyzed the coupling reaction of aryl bromides and chlorides with amines to afford the corresponding products in good to excellent yields. The efficiency is likely derived from an interaction between the palladium center and the cis‐aryl moiety on the diarylvinylphosphine ligand stabilizing a catalytic intermediate during the coupling reaction.     

Controllable Magnetic Proximity Effect and Charge Transfer in 2D Semiconductor and Double-Layered Perovskite Manganese Oxide van der Waals Heterostructure

Optically generated excitonic states (excitons and trions) in transition metal dichalcogenides are highly sensitive to the electronic and magnetic properties of the materials underneath. Modulation and control of the excitonic states in a novel van der Waals (vdW) heterostructure of monolayer MoSe₂ on double-layered perovskite Mn oxide ((La_0.8Nd_0.2)_1.2Sr_1.8Mn₂O₇) is demonstrated, wherein the Mn oxide transforms from a paramagnetic insulator to a ferromagnetic metal. A discontinuous change in the exciton photoluminescence intensity via dielectric screening is observed. Further, a relatively high trion intensity is discovered due to the charge transfer from metallic Mn oxide under the Curie temperature. Moreover, the vdW heterostructures with an ultrathin h-BN spacer layer demonstrate enhanced valley splitting and polarization of excitonic states due to the proximity effect of the ferromagnetic spins of Mn oxide. The controllable h-BN thickness in vdW heterostructures reveals a several-nanometer-long scale of charge transfer as well as a magnetic proximity effect. The vdW heterostructure allows modulation and control of the excitonic states via dielectric screening, charge carriers, and magnetic spins.     

All-fiber quasi-continuous wave supercontinuum generation in single-mode high-nonlinear fiber pumped by submicrosecond pulse with low peak power

We demonstrate quasi-continuous wave supercontinuum generation in a single-mode high-nonlinear fiber (HNLF) in 1.55 μm band, which is pumped by the amplified passively Q-switched submicrosecond pulse. The pump wavelength is in the normal dispersion region of HNLF and near to the zero-dispersion wavelength. The broad SC spectral range from 1200 to 2260 nm is obtained with the low pump peak power of 17.8 W. The 20 dB bandwidth of 922 nm from 1285 to 2207 nm is obtained with the assumption that the peak near 1560 nm is filtered. The spectrum density for the 20 dB bandwidth is from -27.5 to -7.5 dbm/nm.     

Effects of Sulfur and a Lubricity Improver on the Tribological Characteristics of Si3N4 Ceramics against Steel in Fuel

The effects of sulfur (dibenzothiophene) and a lubricity improver (glyceride) on the tribological behavior of combinations of Si₃N₄ ceramics and steel were investigated in kerosene at 373 K. The tests were performed by sliding the circumferential surface of a rotating disk with two plates. Lubricity was not improved by the addition of glyceride for the combination of the different materials. The oxidation wear of the Si₃N₄ was considered to have occurred by a trace amount of water as an impurity in the kerosene. The steel plate was mainly removed by mechanical wear, which was accelerated by increasing the sulfur concentration.