Institute of Advanced Energy, Kyoto University

We studied multiexciton dynamics in monolayer ${\mathrm{WSe}}_{2}$ using nonlinear photoluminescence (PL) spectroscopy and Monte Carlo simulations. We observed strong nonlinear saturation behavior of exciton PL with increasing excitation power density and long-distance exciton diffusion, reaching several micrometers. We demonstrated that the diffusion-assisted exciton-exciton annihilation (EEA) model accounts for the observed nonlinear PL behavior. The long-distance exciton diffusion and subsequent efficient EEA process determined the unusual multiexciton dynamics in atomically thin layered transition metal dichalcogenides.

Point the finger: Zinc-finger proteins are convenient and site-selective adaptors for targeting specific locations within DNA-origami structures. Orthogonal targeting of the specific locations in the structures was demonstrated by using two adaptors, and the application of Escherichia coli lysate that contained the adaptor-fused proteins successfully afforded the expected protein–DNA assembly.

We describe photoluminescence (PL), PL excitation, and time-resolved PL spectroscopy of hetero-bilayers comprising monolayers (1L) of MoS2 and MoSe2 at cryogenic temperatures. A PL peak showing a decay time of 2.5 ns was observed below 100 K, which can be attributed to an inter-layer exciton emission in the 1L-MoS2/1L-MoSe2 hetero-bilayers. An inter-layer exciton binding energy of ∼90 meV is determined from its thermal dissociation behavior; the band offset of each layer obtained from this value is consistent with previously reported first-principles calculations. Moreover, generation of inter-layer charged excitons (trions) is implied from the gate modulation of the inter-layer exciton PL spectra.

During eukaryotic translation initiation, eIF3 binds the solvent-accessible side of the 40S ribosome and recruits the gate-keeper protein eIF1 and eIF5 to the decoding center. This is largely mediated by the N-terminal domain (NTD) of eIF3c, which can be divided into three parts: 3c0, 3c1, and 3c2. The N-terminal part, 3c0, binds eIF5 strongly but only weakly to the ribosome-binding surface of eIF1, whereas 3c1 and 3c2 form a stoichiometric complex with eIF1. 3c1 contacts eIF1 through Arg-53 and Leu-96, while 3c2 faces 40S protein uS15/S13, to anchor eIF1 to the scanning pre-initiation complex (PIC). We propose that the 3c0:eIF1 interaction diminishes eIF1 binding to the 40S, whereas 3c0:eIF5 interaction stabilizes the scanning PIC by precluding this inhibitory interaction. Upon start codon recognition, interactions involving eIF5, and ultimately 3c0:eIF1 association, facilitate eIF1 release. Our results reveal intricate molecular interactions within the PIC, programmed for rapid scanning-arrest at the start codon.

The origin of near-infrared (NIR) luminescence from graphene oxide (GO) is investigated by photoluminescence (PL) excitation spectroscopy, time-resolved PL spectroscopy, and density functional theory based many body perturbation theories. The energy of experimentally observed NIR PL peak depends on the excitation energy, and the peak broadens with increasing excitation energy. It is found that the PL decay curves in time-resolved spectroscopy show build-up behavior at lower emission energies due to energy transfer between smaller to larger graphene nanodisc (GND) states embedded in GO. We demonstrate that the NIR PL originates from ensemble emission of GND states with a few nanometers in size. The theoretical calculations reveal the electronic and excitonic properties of individual GND states with various sizes, which accounts for the inhomogeneously broadened NIR PL. We further demonstrate that the electronic properties are highly sensitive to the protonation and deprotonation processes of GND states using both the experimental and theoretical approaches.

In order to understand intracellular biological events, information on the structure, dynamics and interaction of proteins and nucleic acids in living cells is of crucial importance. In-cell NMR is a promising method to obtain this information. Although NMR signals of proteins in human cells have been reported, those of nucleic acids were reported only in Xenopus laevis oocytes, i.e., not in human cells. Here, DNA and RNA were introduced into human cells by means of pore formation by bacterial toxin streptolysin O and subsequent resealing. Then, NMR signals of DNA and RNA were successfully observed for the first time in living human cells. The observed signals directly suggested the formation of DNA and RNA hairpin structures in living human cells.

We focused on the effects of a mutation of xylose reductase from Pichia stipitis (PsXR) on xylose-to-ethanol fermentation using recombinant Saccharomyces cerevisiae transformed with PsXR and PsXDH (xylitol dehydrogenase from P. stipitis) genes. Based on inherent NADH-preferring XR and several site-directed mutagenetic studies using other aldo-keto reductase enzymes, we designed several single PsXR mutants. K270R showing decreased NADPH-preferring activity without a change in NADH-preferring activity was found to be a potent mutant. Strain Y-K270R transformed with K270R PsXR and wild-type PsXDH showed a 31% decrease in unfavorable xylitol excretion with 5.1% increased ethanol production as compared to the control in the fermentation of 15 g l(-1) xylose and 5 g l(-1) glucose.

We have developed a free-energy function based on an all-atom model for proteins. It comprises two components, the hydration entropy (HE) and the total dehydration penalty (TDP). Upon a transition to a more compact structure, the number of accessible configurations arising from the translational displacement of water molecules in the system increases, leading to a water-entropy gain. To fully account for this effect, the HE is calculated using a statistical-mechanical theory applied to a molecular model for water. The TDP corresponds to the sum of the hydration energy and the protein intramolecular energy when a fully extended structure, which possesses the maximum number of hydrogen bonds with water molecules and no intramolecular hydrogen bonds, is chosen as the standard one. When a donor and an acceptor (e.g., N and O, respectively) are buried in the interior after the break of hydrogen bonds with water molecules, if they form an intramolecular hydrogen bond, no penalty is imposed. When a donor or an acceptor is buried with no intramolecular hydrogen bond formed, an energetic penalty is imposed. We examine all the donors and acceptors for backbone-backbone, backbone-side chain, and side chain-side chain intramolecular hydrogen bonds and calculate the TDP. Our free-energy function has been tested for three different decoy sets. It is better than any other physics-based or knowledge-based potential function in terms of the accuracy in discriminating the native fold from misfolded decoys and the achievement of high Z-scores.

The review paper has systematically summarized and proposed research-based guidance for recycling organic–inorganic perovskite solar cells and ecofriendly fabrication.

R3 and for NFAT nuclear translocation. Pharmacological inhibition of ITPKB in mice reduced both LPS-induced tissue swelling and the severity of inflammatory arthritis to a similar extent as that induced by the inhibition of NFAT using nanoparticles that delivered an NFAT-inhibiting peptide specifically to phagocytic cells. Our results suggest that ITPKB may represent a promising target for anti-inflammatory therapies that aim to inhibit specific DC functions.

Fast fracture properties of chemically vapor-infiltrated silicon carbide matrix composites with Hi-NicalonTM Type-S near-stoichiometric silicon carbide fiber reinforcements and thin pyrolytic carbon interphase were studied. The primary emphasis was on preliminary assessment of the applicability of a very thin pyrolytic carbon interphase between fibers and matrices of silicon carbide composites for use in nuclear environments. It appears that the mechanical properties of the present composite system are not subject to strong interphase thickness effects, in contrast to those in conventional non-stoichiometric silicon carbide-based fiber composites. The interphase thickness effects are discussed from the viewpoints of residual thermal stress, fiber damage, and interfacial friction. A preliminary conclusion is that a thin pyrolytic carbon interphase is beneficial for fast fracture properties of stoichiometric silicon carbide composites.

We studied an evaluation method of photoluminescence (PL) quantum yield of monolayer transition metal chalcogenides (TMDs) on a transparent substrate using a reference dye. A 3‐borylbithiophene derivative (C 58 H 49 BN 2 S 4 ) reference dye shows a high PL quantum yield of 36% even in the solid form and the high quantum yield is kept in a Poly(methyl methacrylate) (PMMA) matrix. Moreover, the photon energy of PL is similar to those of monolayer TMDs. These PL characteristics of the reference dye are useful for a evaluation of PL quantum yield in monolayer TMDs. The PL quantum yield of 0.18 ± 0.03% was evaluated for mechanically exfoliated monolayer WSe 2 on glass substrate at room temperature.

Visible imaging measurement using a fast camera in conjunction with a gas puff was demonstrated in the GAMMA 10 tandem mirror. In order to image plasma behavior on the periphery, a hydrogen gas puff in the bottom of the vacuum chamber near the GAMMA 10 central-cell was used. Without the gas puff the light emission was not sufficiently bright, and SN ratio is not good. By using the gas puff, the light emission could be clearly observed, and a 5 - 6 kHz vibration of the plasma column was confirmed. This motion is most likely plasma rotation due to the electron drift wave and Er × B drift. These results show that the fast camera used in conjunction with a gas puff is a promising candidate for the measurement of peripheral plasma behavior even in low-density mirror plasmas.

K-ion battery is a potential candidate as a next-generation battery with a high energy density, long cycle life, and high safety. To commercialize the battery, the improvement of safety is absolutely essential. We apply a nonflammable ionic-liquid electrolyte to a Sn 4 P 3 electrode as negative-electrode for K-ion battery. The electrode achieves the excellent cycling performance with a discharge capacity of 365 mA h g -1 over 100 cycles in the ionicliquid electrolyte. Rate capability in the ionic-liquid electrolyte is almost the same as that in the organic-liquid electrolyte.

Oxide dispersion strengthened (ODS) steels with nano-scaled oxide particles in high density in ferrite/martensite matrix and on grain boundaries of ultra-fine grains have excellent properties as structural material for fusion blankets, while some issues of fabrication processes are still remaining to be solved. In this overview, material properties of recently developed ODS steels are introduced in comparison to ferritic/martensitic (F/M) steels: 1) mechanical properties, 2) corrosion behavior and 3) radiation tolerance in ODS steels, which are outstandingly superior to the F/M steels. Coupling use of the ODS and F/M steels is effective to expand the design margin of fusion blankets. R&D of dissimilar joining of FM/ODS steels is indispensable.

The moiré superlattice consisting of lattice- or angular-mismatched van der Waals heterostructures drastically changes the physical properties of constituent atomically thin materials by confinement of the exciton by the moiré potential, which is promising for next-generation quantum optics. The moiré superlattice also affects the valley degrees of freedom of the monolayer transition-metal dichalcogenides (TMDs) and the valley-dependent optical selection rule, which results in the characteristic circular polarized light emission of the moiré exciton. However, the valley relaxation process of excitons in the moiré superlattice remains to be understood. Here, we studied valley relaxation of moiré excitons in a twisted WSe2/MoSe2 heterobilayer by circularly polarized photoluminescence and photoluminescence excitation (PLE) spectroscopy. The experimentally observed circularly polarized emission strongly depends on the excitation power density, which contrasts with the case of two-dimensional monolayer TMDs. The excitation power-dependent circularly polarized emission suggests the characteristic valley relaxation of the moiré exciton with a small density of states in zero-dimensional systems. In addition, the resonant PLE measurement reveals the intravalley relaxation process from the triplet to singlet state of the moiré exciton via Γ5 phonon emission. Our findings clarified the valley relaxation of the moiré excitons, which would lead to the application of the circularly polarized quantum light emitter in twisted semiconducting heterobilayers.

Don′t shoot the messenger! An optical sensor for D-myo-inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), an intracellular second messenger, is constructed by introducing a fluorophore at a unique cysteine residue within a mutant of the pleckstrin homology (PH) domain of the general receptor for phosphoinositides 1 (GRP1). The biosensor visualizes the Ins(1,3,4,5)P4 dynamics by agonist stimulation in single live cells.

The capability of acousto-optic modulator (AOM) to perform time-gated measurements for laser ablation plasma spectroscopy has been examined. Especially, we focused on the capability of the "AOM gating" to exclude the continuum and extremely broadened spectra usually observed immediately after the laser ablation. Final goal of the use of the AOM is to achieve considerable downsizing of the system for in situ and on-site analyses. In the present paper, it is shown that narrow and clear spectral lines can be obtained with the AOM gating even if the target is submerged in water. Also, application of this technique to the targets in air is demonstrated. It has been revealed that the AOM gating is fast enough to exclude the continuum and broadened lines, while effectively acquiring sufficiently narrow atomic lines lasting slightly longer than the continuum.

Ratiometric fluorescent sensors were constructed from RNA aptamers by generating modular ribonucleopeptide complexes. Fluorescent ribonucleopeptides containing fluorophore seminaphthorhodafluor tethered to their peptide subunit revealed a dual emission property, which permitted a ratiometric fluorescent measurement of a substrate-binding event. The strategy successfully afforded ratiometric fluorescent sensors for biologically active small ligands, tetracycline, dopamine and streptomycin.

Interlayer excitons (IXs) in the heterostructure of monolayer transition metal dichalcogenides (TMDs) are considered as a promising platform to study fundamental exciton physics and for potential applications of next generation optoelectronic devices. The IXs trapped in the moiré potential in a twisted monolayer TMD heterostructure such as MoSe 2 /WSe 2 form zero-dimensional (0D) moiré excitons. Introducing an atomically thin insulating layer between TMD monolayers in a twisted heterostructure would modulate the moiré potential landscape, thereby tuning 0D IXs into 2D IXs. However, the optical characteristics of IXs have not been elucidated. Here, we have experimentally investigated the significant optical characteristics arising from IXs in a MoSe 2 / h -BN/WSe 2 heterostructure by optical spectroscopy. The experimental results of time-resolved photoluminescence spectroscopy combined with phenomenological rate equation analysis reveal that the radiative decay rate of IXs in the MoSe 2 / h -BN/WSe 2 heterostructure changes as a function of temperature, which strongly suggests the emergence of 2D IXs by the modulation of potential. Moreover, we demonstrate the valley polarization arising from the prolonged valley relaxation lifetime of 2D IXs reaching 100 ns at low temperature, which is dominated by electron–hole exchange interactions. These findings provide us with an effective strategy to tailor the dimensionality of IXs and elucidate the desired optoelectronic response of IXs in monolayer semiconductor heterostructures.