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Fructans such as inulin and levan accumulate in certain taxonomic groups of plants and are a reserve carbohydrate alternative to starch. Onion (Allium cepa L.) is a typical plant species that accumulates fructans, and it synthesizes inulin-type and inulin neoseries-type fructans in the bulb. Although genes for fructan biosynthesis in onion have been identified so far, no genes for fructan degradation had been found. In this study, phylogenetic analysis predicted that we isolated a putative vacuolar invertase gene (AcpVI1), but our functional analyses demonstrated that it encoded a fructan 1-exohydrolase (1-FEH) instead. Assessments of recombinant proteins and purified native protein showed that the protein had 1-FEH activity, hydrolyzing the β-(2,1)-fructosyl linkage in inulin-type fructans. Interestingly, AcpVI1 had an amino acid sequence close to those of vacuolar invertases and fructosyltransferases, unlike all other FEHs previously found in plants. We showed that AcpVI1 was localized in the vacuole, as are onion fructosyltransferases Ac1-SST and Ac6G-FFT. These results indicate that fructan-synthesizing and -degrading enzymes are both localized in the vacuole. In contrast to previously reported FEHs, our data suggest that onion 1-FEH evolved from a vacuolar invertase and not from a cell wall invertase. This demonstrates that classic phylogenetic analysis on its own is insufficient to discriminate between invertases and FEHs, highlighting the importance of functional markers in the nearby active site residues.

Terahertz (THz) time-domain emission spectroscopy was performed on layered 2H-MoSe 2 and 2H-WSe 2. The THz emission shows an initial cycle attributed to surge currents and is followed by oscillations attributed to coherent interlayer phonon modes. To obtain the frequencies of the interlayer vibrations, an analysis of the THz emission waveforms was performed, separating the two contributions to the total waveform. Results of the fitting show several vibrational modes in the range of 5.87–32.75 cm − 1 for the samples, attributed to infrared-active interlayer shear and breathing modes. This study demonstrates that THz emission spectroscopy provides a means of observing these low-frequency vibrational modes in layered materials.

Squeezing bubbles and impurities out of interlayer spaces by applying force through a few-layer graphene capping layer leads to van der Waals heterostructures with the ultraflat structure free from random electrostatic potential arising from charged impurities. Without the graphene capping layer, a squeezing process with an AFM tip induces applied-force-dependent charges of Δn ∼ 2 × 1012 cm-2 μN-1, resulting in the significant intensity of trions in photoluminescence spectra of MoSe2 at low temperature. We found that a hBN/MoSe2/hBN prepared with the "graphene-capping-assisted AFM nano-squeezing method" shows a strong excitonic emission with negligible trion peak, and the residual line width of the exciton peak is only 2.2 meV, which is comparable to the homogeneous limit. Furthermore, in this high-quality sample, we found that the formation of biexciton occurs even at extremely low excitation power (Φph ∼ 2.3 × 1019 cm-2 s-1) due to the enhanced collisions between excitons.

Van der Waals heterostructures are the ideal material platform for tunnel field effect transistors (TFETs) because a band-to-band tunneling (BTBT) dominant current is feasible at room temperature (RT) due to ideal, dangling bond free heterointerfaces. However, achieving subthreshold swing (SS) values lower than 60 mVdec-1 of the Boltzmann limit is still challenging. In this work, we systematically studied the band alignment and heterointerface quality in n-MoS2 channel heterostructure TFETs. By selecting a p+-MoS2 source with a sufficiently high doping level, stable gate modulation to a type III band alignment was achieved regardless of the number of MoS2 channel layers. For the gate stack formation, it was found that the deposition of Al2O3 as the top gate introduces defect states for the generation current under reverse bias, while the integration of an h-BN top gate provides a defect-free, clean interface, resulting in the BTBT dominant current even at RT. All 2D heterostructure TFETs produced by combining the type III n-MoS2/p+-MoS2 heterostructure with the h-BN top gate insulator resulted in low SS values at RT.

The crystal structure of a material creates a periodic potential that electrons move through giving rise to the electronic band structure of the material. When two-dimensional materials are stacked, the twist angle between the layers becomes an additional degree freedom for the resulting heterostructure. As this angle changes, the electronic band structure is modified leading to the possibility of flat bands with localized states and enhanced electronic correlations. In transition metal dichalcogenides, flat bands have been theoretically predicted to occur for long moir\'e wavelengths over a range of twist angles around 0 and 60 degrees giving much wider versatility than magic angle twisted bilayer graphene. Here we show the existence of a flat band in the electronic structure of 3{\deg} and 57.5{\deg} twisted bilayer WSe2 samples using scanning tunneling spectroscopy. Direct spatial mapping of wavefunctions at the flat band energy have shown that the flat bands are localized differently for 3{\deg} and 57.5{\deg}, in excellent agreement with first-principle density functional theory calculations., Comment: 15 pages, 4 figures. Added data for 57 degree twist angle sample

We report enhanced interlayer tunneling with reduced linewidth at zero interlayer bias in a twist-controlled double monolayer graphene heterostructure in the quantum Hall regime, when the top ($\nu_{\mathrm{T}}$) and bottom ($\nu_{\mathrm{B}}$) layer filling factors are near $\nu_{\mathrm{T}}=\pm1/2, \pm3/2$ and $\nu_{\mathrm{B}}=\pm1/2, \pm3/2$, and the total filling factor $\nu = \pm1$ or $\pm3$. The zero-bias interlayer conductance peaks are stable against variations of layer filling factor, and signal the emergence of interlayer phase coherence. Our results highlight twist control as a key attribute in revealing interlayer coherence using tunneling., Comment: 5 pages, 4 figures, includes supplementary material

We report the fabrication of self-assembled surface-passivated [CH(NH2)2]0.8Cs0.2PbI3 thin films using a one-step method with a fluorinated polymer (FP) as an additive without post-treatment. The F...

In van der Waals (vdW) heterostructures formed by stacking two monolayers of transition metal dichalcogenides, multiple exciton resonances with highly tunable properties are formed and subject to both vertical and lateral confinement. We investigate how a unique control knob, the twist angle between the two monolayers, can be used to control the exciton dynamics. We observe that the interlayer exciton lifetimes in $\text{MoSe}_{\text{2}}$/$\text{WSe}_{\text{2}}$ twisted bilayers (TBLs) change by one order of magnitude when the twist angle is varied from 1$^\circ$ to 3.5$^\circ$. Using a low-energy continuum model, we theoretically separate two leading mechanisms that influence interlayer exciton radiative lifetimes. The shift to indirect transitions in the momentum space with an increasing twist angle and the energy modulation from the moir\'e potential both have a significant impact on interlayer exciton lifetimes. We further predict distinct temperature dependence of interlayer exciton lifetimes in TBLs with different twist angles, which is partially validated by experiments. While many recent studies have highlighted how the twist angle in a vdW TBL can be used to engineer the ground states and quantum phases due to many-body interaction, our studies explore its role in controlling the dynamics of optically excited states, thus, expanding the conceptual applications of "twistronics".

We investigated the synthesis of amorphous aluminum titanium oxide Al1− xTi xO y thin films from a Al(acac)3 and Ti(acac)4 mixture using CH3OH/H2O as a solvent through mist chemical vapor deposition (mist-CVD) for application as a high dielectric material. The Ti composition ratio x in the Al1− xTi xO y thin films depends on the Al(acac)3 and Ti(acac)4 mixing ratios and CH3OH/H2O volume ratio. A bandgap energy of Al1− xTi xO y films was decreased from 6.38 to 4.25 eV and the surface roughness also decreased when the Ti composition ratio was increased from 0 to 0.54. The capacitance–voltage plot revealed that the dielectric constant of Al1− xTi xO y thin films increased from 6.23 to 25.12. Consequently, Al1− xTi xO y thin films with a bandgap energy of 5.12 eV and a dielectric constant of 13.8 were obtained by adjusting the ratio x of 0.26. This Al0.74Ti0.26O y layer was applied as a gate dielectric layer for metal-oxide-semiconductor field-effect transistors (MOSFETs) using a mechanically exfoliated two-dimensional (2D) transition metal dichalcogenide (TMDC), MoSe2, and As-doped WSe2 flakes as a channel layer. The MoSe2-based MOSFETs with source/drain gold electrodes exhibit n-channel behavior with a field-effect mobility of 85 cm2/(V s), a threshold voltage of 0.92 V. On the other hand, an on/off ratio of ∼106. As-doped WSe2-based MOSFETs with source/drain platinum electrodes also showed an ambipolar behavior, which was applied for use in logic applications. These findings suggest that Al0.74Ti0.26O y by mist-CVD is promising as a high- k material for TMDC-based MOSFETs.

Asparagus (Asparagus officinalis L.) accumulates inulin- and inulin neoseries-type fructans. Fructose released by the hydrolysis of fructans is an energy source for emerging asparagus spears. Plant fructans are hydrolyzed by fructan exohydrolases (FEHs), whose presence in asparagus has not yet been fully characterized. Here, we describe for the first time the purification and characterization of an FEH from asparagus, and the functional analysis of its gene. The purified enzyme was predicted to exist as a dimer (approximately 130 kDa) consisting of two polypeptides with a molecular mass of approximately 68 kDa. N-terminal sequences of the purified enzyme were matched with the amino acid sequences of aoeh4a and aoeh4b cDNAs isolated from asparagus (cv. Gijnlim and Taihouwase). Native enzymes obtained from asparagus roots and recombinant enzymes produced by Pichia pastoris showed fructan 1-exohydrolase (1-FEH) activity via the hydrolysis of inulin-type fructan. Unlike other 1-FEHs, these enzymes showed minimal hydrolysis of 1-kestose but efficiently hydrolyzed neokestose. Therefore, the enzyme was termed 6G&1-FEH. Gene expression studies in asparagus roots showed that aoeh4 increased during root storage at 2 °C and spear harvesting. These findings suggest that 6G&1-FEH may be involved in fructan hydrolysis in asparagus roots to provide an energy source for emerging asparagus spears.

Realization of unconventional physical properties in two-dimensional (2D) transition-metal dichalcogenides (TMDs) is currently one of the key challenges in condensed-matter systems. However, the electronic properties of 2D TMDs remain largely unexplored compared to those of their bulk counterparts. Here, we report the fabrication of a high-quality monolayer NbSe2 film with a trigonal prismatic structure by molecular beam epitaxy, and the study of its electronic properties by scanning tunneling microscopy, angle-resolved photoemission spectroscopy, and electrical transport measurements, together with first-principles band-structure calculations. In addition to a charge density wave (CDW) with 3 × 3 periodicity and superconductivity below 1.5 K, we observed sizable (~0.1 eV) band splitting along the Γ-K cut in the Brillouin zone due to inversion symmetry breaking in the monolayer crystal. This splitting is highly anisotropic in k space, leading to a spin-split van-Hove singularity in the band structure. The present results suggest the importance of spin–orbit coupling and symmetry breaking for unconventional superconductivity and CDW properties in monolayer TMDs. The interplay between symmetry breaking, superconductivity and charge density wave in monolayer NbSe2 is unveiled by spectroscopic techniques. A team led by Takafumi Sato at Tohoku University used molecular beam epitaxy to fabricate atomically thin NbSe2 films on bilayer graphene, and investigated their electronic properties by a combination of electrical transport measurements, scanning tunneling microscopy, and angle-resolved photoemission spectroscopy. A charge density wave transition with a strong periodic charge modulation was detected below 1.5 K, accompanied by the emergence of superconductivity. Owing to the inversion symmetry breaking occurring in monolayer NbSe2, a band splitting developed along the Γ-Κ direction of the Brillouin zone. Such band splitting was found to be related to the robustness of the observed superconductivity, as well as the formation of the charge density wave.

In this work, by combining transmission electron microscopy and polarized Raman spectroscopy for the 1T′ MoTe2 flakes with different thicknesses, we found that the polarization dependence of Raman intensity is given as a function of excitation laser wavelength, phonon symmetry, and phonon frequency, but has weak dependence on the flake thickness from few-layer to multilayer. In addition, the frequency of Raman peaks and the relative Raman intensity are sensitive to flake thickness, which manifests Raman spectroscopy as an effective probe for thickness of 1T′ MoTe2. Our work demonstrates that polarized Raman spectroscopy is a powerful and nondestructive method to quickly identify the crystal structure and thickness of 1T′ MoTe2 simultaneously, which opens up opportunities for the in situ probe of anisotropic properties and broad applications of this novel material.

We have investigated the fabrication process of organic–inorganic perovskite {CH(NH2)2}1−xCsxPbI3 thin films on compact TiO2 layers by the reaction of porous PbCsxI2+x layers and CH(NH2)2I solution. The perovskite thin films have compact pore-free surfaces with minimal surface roughness. A planar-structured {CH(NH2)2}1−xCsxPbI3 thin film solar cell with x = 0.2 exhibited a power conversion efficiency of 14.7% in reverse scan.

We have performed angle-resolved photoemission spectroscopy on transition-metal dichalcogenide $1T\text{\ensuremath{-}}{\mathrm{HfTe}}_{2}$ to elucidate the evolution of electronic states upon potassium (K) deposition. In pristine ${\mathrm{HfTe}}_{2}$, an in-plane hole pocket and electron pockets are observed at the Brillouin-zone center and corner, respectively, indicating the semimetallic nature of bulk ${\mathrm{HfTe}}_{2}$, with dispersion perpendicular to the plane. In contrast, the band structure of heavily K-dosed ${\mathrm{HfTe}}_{2}$ is obviously different from that of bulk and resembles the band structure calculated for monolayer ${\mathrm{HfTe}}_{2}$. It was also observed that lightly K-dosed ${\mathrm{HfTe}}_{2}$ is characterized by quantized bands originating from bilayer and trilayer ${\mathrm{HfTe}}_{2}$, indicative of staging. The results suggest that the dimensionality crossover from 3D (dimensional) to 2D electronic states due to systematic K intercalation takes place via staging in a single sample. The study provides a strategy for controlling the dimensionality and functionality of novel quantum materials.

Optical responses from two-dimensional semiconductors, such as monolayer transition metal dichalcogenides (TMDs), are dominated by excitonic effects due to strong Coulomb interaction between electrons and holes. Diffusion of excitons is, therefore, one of the most important processes to understand optical responses in 2D semiconductors. In this work, we have prepared a high-quality TMD, monolayer MoSe 2 encapsulated by hBN flakes (hBN/MoSe2/hBN), and investigated intrinsic exciton diffusion at various temperatures ranging from 10 ∼ 300 K. We found that Exciton mobility in hBN/MoSe 2 /hBN monotonically increases as temperature decreases, and mobility at 10 K reaches over 104 cm2V−1s−1.

The synthesis of the saccharide β-D-fructopyranosyl-(2→6)-D-glucopyranose, which was isolated from Super Ohtaka®, has recently been reported. During the synthesis of this saccharide, the formation of two novel saccharides from D-glucose and D-fructose was observed. The present study aimed to confirm the structures of the two disaccharides synthesized from D-glucose and D-fructose by thermal treatment. Furthermore, various properties of the saccharides were investigated. Both saccharides were isolated from the reaction mixture by carbon-Celite column chromatography and an HPLC system and were determined to be novel sucrose-isomers, β-D-fructopyranosyl-(2↔1)-β-D-glucopyranoside (1) and β-D-fructofuranosyl-(2↔1)-β-D-glucopyranoside (2), by MALDI-TOF MS and NMR analyses. Both saccharides showed low digestibility in vitro, and the sweetness of saccharide 2 was 0.45 times that of sucrose.

A fermented beverage of plant extracts (Super Ohtaka®) was prepared from about 50 kinds of fruits and vegetables. This natural fermentation was performed by yeast (Zygosaccharomyces spp. and Pichia spp.) and lactic acid bacteria (Leuconostoc spp.) and resulted in the production of a novel fructopyranose-containing saccharide, which was subsequently isolated using carbon-Celite column chromatography and preparative-HPLC. The structure of the saccharide was determined using MALDI-TOF MS and NMR, and the saccharide was identified as β-D-fructopyranosyl-(2→6)-β-D-fructofuranosyl-(2↔1)-α-D-glucopyranoside. This is the first description of this novel saccharide and its isolation from a natural source.

High-quality large-area few-layer 1T' MoTe2 films with high homogeneity are synthesized by the controlled tellurization of MoO3 film. The Mo precursor plays a key role in determining the quality and morphology of the 1T' MoTe2 . Furthermore, the amount of Te strongly influences the phase of the MoTe2 . The growth method paves the way toward the scalable production of 1T' MoTe2 -based applications.

The dichlorogallyliron complexes Cp’(OC)2FeGaCl2 (Cp’ = Cp* (4a), Cp (4b), Cp*: η5-C5Me5, Cp: η5-C5H5), when treated with LiPPh2 and/or Me3SiPPh2 in Et2O, produce the four-membered Ga2P2 cyclic diiron complexes [Cp’(OC)2FeGa(Cl)PPh2]2 (Cp’ = Cp* (5a), Cp (5b)) in 64% and 47% yields, respectively. Crystal structure analysis using X-ray crystallography revealed that the four-membered Ga2P2 cyclic structure in cis-5a is slightly puckered. The four-membered Ga2P2 cyclic structure remains undisturbed in a solution of complex 5a in C6D6 and C7D8. 5a exists as a mixture of the cis/trans geometric isomers in these solutions. The photochemical reaction with complex 5b in C6D6 produces a complex mixture. However, the photochemical reaction with complex 5a in C6D6 afforded the six-membered Fe-Ga-Fe-P-Ga-P cyclic diiron complex [{Cp*(OC)Fe}2(μ-Ga)(μ-Ph2PGaCl2PPh2)] (6a) in 61% yield (NMR yield). Crystal structure analysis revealed that complex 6a contains the Ga atom-bridged Fe-Ga-Fe fragment with two Fe−Ga multiple bonds.

The memory window of floating gate (FG) type non-volatile memory (NVM) devices is a fundamental figure of merit used not only to evaluate the performance, such as retention and endurance, but also to discuss the feasibility of advanced functional memory devices. However, the memory window of two dimensional (2D) materials based NVM devices is historically determined from round sweep transfer curves, while that of conventional Si NVM devices is determined from high and low threshold voltages (Vths), which are measured by single sweep transfer curves. Here, it is elucidated that the memory window of 2D NVM devices determined from round sweep transfer curves is overestimated compared with that determined from single sweep transfer curves. The floating gate voltage measurement proposed in this study clarifies that the Vths in round sweep are controlled not only by the number of charges stored in floating gate but also by capacitive coupling between floating gate and back gate. The present finding on the overestimation of memory window enables to appropriately evaluate the potential of 2D NVM devices.

Aluminum oxide (AlOx) thin films were grown using aluminum acetylacetonate [Al(acac)3] as a source material with methanol and water as the solvent by mist chemical vapor deposition, while also exposing some films to water or methanol mists after fabrication. The incorporation of –OH groups into the AlOx network that is fabricated from Al(acac)3 and using solely methanol as a solvent generates both malformed Al(OH) network and nonuniformity. However, the addition of a small amount of water in the solvent during film growth decreases the deposition rate due to the hydrogen bond in water molecules but markedly removes –OH groups from the growth surface of the AlOx network and improves the surface uniformity. The AlOx thin films grown with a methanol:water ratio of 7:3 at 400 °C exhibit a recombination velocity of 16 cm/s, a breakdown field of 6.9 MV/cm, and an interface trap density of 4.2 × 1010 cm−2 eV−1, which are compatible with the AlOx grown by the other vacuum-based methods.

Although semiconductor to metal phase transformation of MoTe$_{2}$ by high-density laser irradiation of more than 0.3 MW/cm$^{2}$ has been reported, we reveal that the laser-induced-metal (LIM) phase is not the 1T' structure derived by a polymorphic-structural phase transition but consists instead of semi-metallic Te induced by photo-thermal decomposition of MoTe$_{2}$. The technique is used to fabricate a field effect transistor with a Pd/2H-MoTe$_{2}$/LIM structure having an asymmetric metallic contact, and its contact properties are studied via scanning gate microscopy. We confirm that a Schottky barrier (a diffusion potential) is always formed at the Pd/2H-MoTe$_{2}$ boundary and obstacles a carrier transport while an Ohmic contact is realized at the 2H-MoTe$_{2}$/LIM phase junction for both n- and p-type carriers., Comment: 18 pages, 4 figures, accepted for publication in Nanotechnology

We report on the dynamics of coherent phonons in semimetal 1T′- MoTe 2 using femtosecond pump-probe spectroscopy. On an ultrafast sub-picosecond timescale at room temperature, a low frequency and long-lifetime shear phonon mode was observed at 0.39 THz, which was previously reported in the form of a characteristic phonon only in the low temperature T d − MoTe 2 phase. Unlike the other optical phonon modes, the shear phonon mode was found to strongly couple with photoexcited carriers. Moreover, the amplitude of the shear mode surprisingly decreased with increasing excitation density, a phenomenon that can be attributed to be a consequence of the lattice temperature increasing after excitation. These results provide useful physical information on ultrafast lattice symmetry switching between the normal semimetal 1T′ and the lattice inversion symmetry breaking Type-II Weyl semimetal T d phases.

Two-dimensional (2D) materials are highly promising for tunnel field effect transistors (TFETs) with low subthreshold swing and high drive current because the shorter tunnel distance and strong gate controllability can be expected from the van der Waals gap distance and the atomically sharp heterointerface formed independently of lattice matching. However, the common problem for 2D-2D TFETs is the lack of highly doped 2D materials with the high process stability as the sources. In this study, we have found that p+-WSe2 doped by charge transfer from a WOx surface oxide layer can be stabilized by transferring it onto a h-BN substrate. Using this p$^+$-WSe$_2$ as a source, we fabricate all-solid-state 2D-2D heterostructure TFETs with an Al2O3 top gate insulator, i.e., type-II p$^+$-WSe$_2$ /MoS$_2$ and type-III p$^+$-WSe$_2$ /WSe$_2$. The band-to-band tunneling and negative differential resistance trends are clearly demonstrated at low temperatures. This work suggests that high doped 2D crystal of the charge transfer type is an excellent choice as sources for TFETs.

By using a technique of thermoreflectance that can precisely measure the thermal conductivity of thin films, we found that the thermal conductivity of ${\mathrm{SrVO}}_{3}\text{\ensuremath{-}}{\mathrm{SrTiO}}_{3}$ multilayer thin films normal to the surface was substantially reduced by decreasing the thickness of each layer. This indicates that a large intrinsic thermal resistance exists at the interface between ${\mathrm{SrVO}}_{3}$ and ${\mathrm{SrTiO}}_{3}$ in spite of the similar phononic properties for these two compounds.

We firstly investigated efficient poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (PEDOT:PSS)/n-type polycrystalline silicon (p-Si) heterojunction solar cells fabricated by chemical mist deposition (CMD) using a high-pressure H 2 O-vapor-treated p-Si prior to organic film deposition. High-pressure H 2 O vapor treatment of the p-Si efficiently suppressed grain boundary defects and improved carrier transport at the PEDOT:PSS/p-Si interface. Furthermore, compared to spin coated devices, the CMD devices demonstrated a more uniform photovoltaic performance. The power conversion efficiency of the PEDOT:PSS/p-Si heterojunction solar cells was 9.7% with a short-circuit current density of 33.5 mA/cm 2 , an open-circuit voltage of 0.54 V, and a fill factor of 0.53. These findings suggest that CMD with a negatively charged mist precursor provides uniform adhesion of PEDOT:PSS on p-Si, resulting in increased photovoltaic performance.

In this work, multiwalled carbon nanotubes (MWCNTs) are separated and cut into short pipes using a green tea solution and embedded at interface of poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cells. Devices fabricated with embedding green tea modified MWCNTs show much better performance (10.02%) than that of a device without MWCNTs (9.2%) due to better hole transportation, easy exciton splitting, and suppression of charge recombination.

We prepare transparent, selfassembled polygonal silver nanowire (AgNW) mesh by bubble template and use as top electrode for a poly (3,4ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-Si hybrid solar cell. Devices were fabricated by pressing the self-assembled AgNW and ITO electrodes onto the surface of the PEDOT:PSS and device performances were compared. In identical transmittances of ITO and self-assembled AgNW (i.e., 87% transmittance at wavelength of 550 nm), the self-assembled AgNW mesh electrodes shows lower sheet resistance (8 Ω/square) with enhanced transparency in the ultraviolet and infrared regions. As a result, a device performance with an efficiency of 9.60% was obtained with the self-assembled electrode compared to 9.07% efficiency from the indium–tin oxide (ITO) electrode under 100 mW/cm2 of AM 1.5 illumination. This study suggests the potential application of a self-assembled AgNW electrode as the transparent conducting electrode for future optoelectronic devices.

We prepare transparent, self-assembled polygonal silver nanowire (AgNW) mesh by bubble template and transferred as top electrode in poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate) (PEDOT:PSS)/n-silicon hybrid solar cell, which shows power conversion efficiency of 10.62% under 100 mW/cm 2 of AM 1.5G illuminations. The self-assembled AgNW mesh electrode exhibited a low sheet resistance (50 Ω/square) with high transmittance (87%) at a wavelength of 550 nm. In self-assembled AgNW mesh, AgNWs are well packed making continuous path for charge collection and transportation. Nevertheless, studies have also been carried out to transfer AgNWs from donor (glass or plastic) to receiver substrates (thermal release tape) and an expected reason for the transfer of AgNWs from thermal release tape to the top of PEDOT:PSS has also been proposed.

The role of an additional solvent thiosemicarbazide (TSC) in the synthesis of a highly crystallized inorganic–organic halide FA0.8Cs0.2PbIxBr3 − x perovskite using the co-solvent N,N-dimethylformamide/1-cyclohexyl-2-pyrrolidone has been investigated. Ellipsometry combined with x-ray diffraction and FTIR spectroscopy was used for characterization purposes. The average crystal grain size increased from several hundred nanometers to 1–1.5 μm with increasing content of TSC in the co-solvent. Ellipsometry and FTIR spectroscopy revealed that the as-deposited perovskite film before thermal annealing was distorted and featured a large number of voids; also, the Pb ions formed complexes with the C˭S groups in TSC, which suppressed the excessive nucleation. Removal of the co-solvent at the thermal annealing stage facilitated the rearrangement of the [Pb(IxBr3 − x)6]4− octahedral structure from a zero-dimensional to a three-dimensional network, which enhanced crystal grain growth.

The synthesis of the saccharide β-D-fructopyranosyl-(2→6)-D-glucopyranose, which was isolated from Super Ohtaka®, has recently been reported. During the synthesis of this saccharide, the formation of two novel saccharides from D-glucose and D-fructose was observed. The present study aimed to confirm the structures of the two disaccharides synthesized from D-glucose and D-fructose by thermal treatment. Furthermore, various properties of the saccharides were investigated. Both saccharides were isolated from the reaction mixture by carbon-Celite column chromatography and an HPLC system and were determined to be novel sucrose-isomers, β-D-fructopyranosyl-(2↔1)-β-D-glucopyranoside (1) and β-D-fructofuranosyl-(2↔1)-β-D-glucopyranoside (2), by MALDI-TOF MS and NMR analyses. Both saccharides showed low digestibility in vitro, and the sweetness of saccharide 2 was 0.45 times that of sucrose.

In this article, the method to fabricate a highly conductive graphene thin film from natural graphite powder through oxidation, exfoliation, deposition and reduction processes will be presented. Subsequently, the application of the graphene thin film to the electrodes of organic thin-film devices will be introduced. Chemically oxidized graphite powder was dispersed in water, and it was exfoliated by sonication or by repeated centrifugation and washing processes to obtain graphene oxide (GO). Successively a GO film was fabricated by coating a substrate with the GO solution, and it was chemically and thermally reduced to produce a highly conductive graphene film. Operation of organic thin film solar cells, which make use of the graphene films as their transparent electrodes, has been demonstrated. To date, the power-conversion ratio as high as 1% is achieved. Good operating performance of organic thin film field-effect transistors, which have graphene source/drain electrodes, is also demonstrated.

Fresh edible burdock roots were stored in soil of 1 m depth underground from November to May. Three fructooligosaccharide derivatives without a terminal glucose residue, designated saccharides 1, 2 and 3, were generated in the stored burdock roots. They were purified from the sugar extract using carbon-Celite column chromatography. Saccharides 1, 2 and 3 have R-sucrose values (retention time of sucrose = 1) of 1.55, 2.15 and 2.73 by HPAEC, reducing terminal, molar ratios (reducing sugar to D-fructose) of 0.50, 0.33 and 0.25 and degrees of polymerization of 2, 3 and 4 by TOF-MS, respectively. Analyses by GLC and NMR confirmed the three different following structures: first was inulobiose [β-D-fructofuranosyl-(2→1)-β-D-fructopyranose], and the two others were inulotriose [β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructopyranose] and inulotetraose [β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructopyranose]. The NMR spectra showed that 70 to 80 % of the terminal fructose residue of the three saccharides is pyranosyl form, while 20 to 30 % is furanosyl form. The ^C_- and ^1H-signals were also assigned by 2D-NMR including COSY, HSQC, HSQC-TOCSY and HMBC. These saccharides could be synthesized by purified burdock fructan:fructan 1-frustosyltransferase from 1-kestose to free D-fructopyranose giving inulobiose and sucrose, while elongation of fructoranosyl units occurred at this trasferred fructofuranosyl residue to produce inuloolisaccharides having one, two and more additional units of fructofuranose. 新鮮ごぼう根を地下1mの土中で11月から翌年の5月まで6カ月間貯蔵した。この貯蔵ごぼうに末端グルコース残基を有しないフルクトオリゴ糖が新しく生成された。このごぼうから抽出した糖液について電気化学検出器付陰イオン交換高速液体クロマトグラフィー(HPAEC)分析を行ったところ，糖1は1- kestose (3a)のあとに溶出され，糖2，3はnystose (4a), fructosylnystose (5a)のあとにそれぞれ溶出された。この糖抽出液について活性炭-セライトカラムクロマトグラフィーを行うことにより糖1，2，3を単離した。糖 1，2，3はHPAECによる相対保持時間(sucrose = 1)，1.55，2.15，2.73を有し，還元末端をそれぞれもっていた。また，糖1，2，3のフルクトースに対する還元糖の比は 0.50，0.33，0.25であることとTOF-MS分析の結果から糖1，2，3の重合度は2，3，4であることがわかった。これらの結果と各糖の NMR分析，糖メチル誘導体のGLC分析結果から，糖1，2，3はそれぞれβ-D-fructofuranosyl-(2→1)-β-D-fructopyranose (inulobiose)，β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructopyranose (inulotriose)，β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructofuranosyl-(2→1)-β-D-fructo-pyranose (inulotetraose)と同定された。13C-NMR分析により各糖の還元末端フルクトース残基の70-80％がピラノース構造をとることがわかった。それぞれの糖の13C-，1H- シグナルの完全帰属も初めて行った。さらに上述のごぼう貯蔵中に生成されたinulobiose，inulotriose，inulotetraoseと同様の糖が，ごぼうから精製したfructan fructan 1-fructosyltransferase (1-FFT)のフルクトシル転移作用により1-kestoseとD-フルクトピラノースから合成されることを初めて見出した。

A dinuclear complex bridged by a substituent-free gallium atom, Cp∗(dmpe)Fe–Ga–Fe(CO)4 (1b: Cp∗ = η-C5Me5, dmpe = Me2PCH2CH2PMe2), was synthesized by the reaction of Cp∗Fe(dmpe)GaCl2 with K2[Fe(CO)4]. Crystal structure analysis of complex 1b showed that the geometry around the gallium atom is essentially linear and the two Fe–Ga bonds are significantly shorter than those of usual single bonds, indicating the multiple bonding character of the Fe–Ga bonds. Comparison of the structure and IR data of 1b and those of Cp∗(dppe)Fe–Ga–Fe(CO)4 (1a: dppe = Ph2PCH2CH2PPh2) revealed that the Fe–Ga bond is sensitive to the electronic character of the metal fragment. The Fe–Ga bond is shortened upon introducing a more π-basic metal fragment.

In noncentrosymmetric materials, the relativistic effect extensively modifies the energy band of magnons as well as that of electrons. With use of microfabricated microwave antennae, we have demonstrated that the propagation of magnons with large momentum is nonreciprocal in a noncentrosymmetric ferromagnet ${\mathrm{LiFe}}_{5}{\mathrm{O}}_{8}$. The nonreciprocity is clearly explained by the effect of the asymmetric magnon band originating from the relativistic Dzyaloshinskii-Moriya interaction. This result may pave a new path to designing a magnonic device based on the relativistic band engineering.

Molecular orientations of pentacene ultrathin films grown on SiO2 substrates were studied without the influence of the atmosphere by vacuum atomic force microscopy (V-AFM) and near edge X-ray absorption fine structure (NEXAFS). The experimental processes from deposition of pentacene to characterization of films were performed under vacuum condition without exposure to the atmosphere. V-AFM and NEXAFS measurements showed that pentacene molecules tend to grow on SiO2 surface with their molecular long axes perpendicular to the substrate surfaces (standing-mode) irrespective of preparation procedure of SiO2 substrate. (c) 2006 Elsevier B.V. All rights reserved., http://www.sciencedirect.com/science/journal/00396028

Recently, we have investigated enzymic production of non-digestible oligosaccharides which have several functional activities as “tertiary functional ingredients” of foods. Fructo-oligosaccharides synthesized from sucrose by Eurotium repense fructosyltransferase had the effect of no elevation of blood glucose or insulin concentrations in rats. Fructosylxyloside formed from sucrose and xylose with fructosyltransferase action of Scopulariopsis brevicaulis cells suppressed serum glucose and insulin responses and / or promoted the absorption of calcium and magnesium ions in rats administered with sucrose. On the other hand, we studied purification and characterization of several fructosyltransferases; sucrose: sucrose 1-fructosyltransferase (1-SST), fructan: fructan 1-fructosyltransferase (1-FFT) and a new enzyme, fructan: fructan 6G-fructosyltransferase (6G-FFT) from asparagus roots. Previously, we reported that the asparagus 1-FFT synthesized new functional oligosaccharides elongated with one or two additional fructose units by fructosyltransfer from 1-kestose to 4G-β-D-galactosylsucrose and the saccharides selectively stimulated growth for Bifidobacteria. In this study, we have tried the isolation and expression of cDNAs encoding 6G-FFT, 1-FFT and 1-SST from asparagus for industrial use. The cDNAs encoding 6G-FFT, 1-FFT and 1-SST were isolated from a cDNA library of asparagus leaves or roots. The isolated cDNAs were named AoFT 1, AoFT 2 and AoFT 3, respectively. The deduced amino acid sequences of these cDNAs showed a high homology with those of plant fructosyltransferases. Expression of these cDNAs was done using Pichia pastoris. The recombinant protein from Pichia transformed with AoFT 1 produced 1F,6G-di-β-D-fructofuranosylsucrose, neokestose and sucrose from 1-kestose, while the transformant with an empty vector produced no saccharides. These results show that 6G-FFT is expressed in P. pastoris. In the same way, recombinant protein from Pichia transformed with AoFT 2 produced nystose from 1-kestose and AoFT 3 recombinant protein produced 1-kestose from sucrose. These results also show that 1-FFT and 1-SST are expressed in P. pastoris. Three recombinant proteins had enzymatic properties similar to those of 6G-FFT, 1-FFT and 1-SST from asparagus roots, respectively.

We study the second-order Raman process of mono- and few-layer MoTe$_2$, by combining {\em ab initio} density functional perturbation calculations with experimental Raman spectroscopy using 532, 633 and 785 nm excitation lasers. The calculated electronic band structure and the density of states show that the electron-photon resonance process occurs at the high-symmetry M point in the Brillouin zone, where a strong optical absorption occurs by a logarithmic Van-Hove singularity. Double resonance Raman scattering with inter-valley electron-phonon coupling connects two of the three inequivalent M points in the Brillouin zone, giving rise to second-order Raman peaks due to the M point phonons. The predicted frequencies of the second-order Raman peaks agree with the observed peak positions that cannot be assigned in terms of a first-order process. Our study attempts to supply a basic understanding of the second-order Raman process occurring in transition metal di-chalcogenides (TMDs) and may provide additional information both on the lattice dynamics and optical processes especially for TMDs with small energy band gaps such as MoTe$_2$ or at high laser excitation energy., Comment: 10 pages, 5 figures