Showing papers by "Takahiko Kondo published in 2023"
TL;DR: In this paper , the Seebeck coefficient and photo-electrochemical responses of rhombohedral boron monosulfide (r-BS) were measured and the properties unique to p-type semiconductors were observed in both measurements, indicating that the synthesized r-BS is a p type semiconductor.
Abstract: Two-dimensional materials have wide ranging applications in electronic devices and catalysts owing to their unique properties. Boron-based compounds, which exhibit a polymorphic nature, are an attractive choice for developing boron-based two-dimensional materials. Among them, rhombohedral boron monosulfide (r-BS) has recently attracted considerable attention owing to its unique layered structure similar to that of transition metal dichalcogenides and a layer-dependent bandgap. However, experimental evidence that clarifies the charge carrier type in the r-BS semiconductor is lacking. In this study, we synthesized r-BS and evaluated its performance as a semiconductor by measuring the Seebeck coefficient and photo-electrochemical responses. The properties unique to p-type semiconductors were observed in both measurements, indicating that the synthesized r-BS is a p-type semiconductor. Moreover, a distinct Fano resonance was observed in Fourier transform infrared absorption spectroscopy, which was ascribed to the Fano resonance between the E(2) (TO) phonon mode and electrons in the band structures of r-BS, indicating that the p-type carrier was intrinsically doped in the synthesized r-BS. These results demonstrate the potential future application prospects of r-BS.
1 citations
TL;DR: In this article , the authors used angle-resolved photoemission spectroscopy (ARPES) to map the band structure of a rhombohedral boron monosulfide (r-BS) powder crystal.
Abstract: Boron-based two-dimensional (2D) materials are an excellent platform for nanoelectronics applications. Rhombohedral boron monosulfide (r-BS) is attracting particular attention because of its unique layered crystal structure suitable for exploring various functional properties originating in the 2D nature. However, studies to elucidate its fundamental electronic states have been largely limited because only tiny powdered crystals were available, hindering a precise investigation by spectroscopy such as angle-resolved photoemission spectroscopy (ARPES). Here we report the direct mapping of the band structure with a tiny (∼20 × 20 μm2) r-BS powder crystal by utilizing microfocused ARPES. We found that r-BS is a p-type semiconductor with a band gap of >0.5 eV characterized by the anisotropic in-plane effective mass. The present results demonstrate the high applicability of micro-ARPES to tiny powder crystals and widen an opportunity to access the yet-unexplored electronic states of various novel materials.
1 citations
TL;DR: A review of the recent progress in hydrogen boride (HB) sheets can be found in this paper , where several unexpected properties of the HB sheets have been reported, including the properties of hydrogenated-borophene (borophane) properties.
Abstract: Hydrogen boride (HB) sheets are two-dimensional materials and polymorphs of hydrogenated borophene (borophane) composed of boron and hydrogen in a 1:1 stoichiometric ratio. Freestanding HB sheets can be synthesized via ion exchange reactions between the protons and magnesium cations in magnesium diboride. Several unexpected properties of the HB sheets have been reported. Here, the recent progress in HB sheets is reviewed. Hydrogen boride (HB) sheets are two-dimensional materials and one of the polymorphs of hydrogenated-borophene (borophane) composed of boron and hydrogen in a 1:1 stoichiometric ratio. The freestanding HB sheets can be synthesized by ion-exchange reactions between the protons and magnesium cations in magnesium diboride. Several unexpected properties of HB sheets have been reported. Here, the recent progress in HB sheets is reviewed.
TL;DR: In this article , an enhanced method for synthesizing sheets of borophane was presented, which incorporated hydrochloric acid into the ion-exchange reaction significantly improved the production yield from 20% to over 50%.
Abstract: We present an enhanced method for synthesizing sheets of borophane. Despite the challenges associated with low efficiency, we discovered that incorporating hydrochloric acid into the ion-exchange reaction significantly improved the production yield from 20% to over 50%. After a thorough examination of the reaction, we gained insight into the underlying mechanisms and found that the use of hydrochloric acid provides two key benefits: accelerated production of borophene and isolation of high-purity products. This method has the potential to pave the way for the production of novel topological 2D materials with potential industrial applications.
TL;DR: In this paper , the intermolecular interactions between single-walled carbon nanotubes (SWCNTs) and encapsulated molecules were investigated under incident laser polarization parallel and perpendicular to the tube axis.
Abstract: In the present study, we investigated the intermolecular interactions between single-walled carbon nanotubes (SWCNTs) and encapsulated molecules by polarization resonance Raman microscopy. C70 encapsulated in SWCNTs is investigated under incident laser polarization parallel and perpendicular to the tube axis. We employed two excitation laser wavelengths 442 and 532 nm, which are in resonance with different electronic states of C70. Under 532 nm excitation, no distinct polarization dependence is found in the Raman spectral pattern, while under 442 nm excitation, a peak not previously seen for this excitation wavelength was clearly observed for parallel excitation. This result can be explained by the modulation of the resonance Raman process via a charge transfer contribution between C70 and the SWCNTs, which is sensitive to the incident polarization as well as the excitation wavelength. The intensity of the local electronic field inside a SWCNT is higher for the parallel excitation than the perpendicular excitation when the nanotubes are in a bundle. The results can be explained by field localization effects at the nanotube walls, qualitatively supported by finite-difference time-domain simulations.
TL;DR: In this paper , an analysis of ultraviolet (UV) photoluminescence (PL) spectra from individual nanostructured ZnO clusters less than 1 μm in size was performed.
Abstract: Ultraviolet (UV) photoluminescence (PL) spectra were acquired from individual nanostructured ZnO clusters less than 1 μm in size. The nanostructured clusters were formed by aggregation of a small number of nanoparticles. This analysis employed a microscopy apparatus specially designed for PL assessments of nanostructures at UV wavelengths with a spatial resolution of 0.395 μm. Atomic force microscopy was also employed to ascertain the sizes and morphologies of the nanostructured clusters. The ZnO samples were prepared by laser ablation in liquid (LAL) and comprised spherical, rhomboid, or gel-coated particles. PL emissions originating from free excitons (FX), FX phonon replicas, and defects were observed. The FX peak widths and positions were found to vary (with positions from 3.30 to 3.36 eV), suggesting that a range of particle sizes and morphologies was obtained from the LAL process. FX peaks at higher energies exhibited greater widths as a consequence of a quantum size effect originating from the crystallites comprising the nanostructured clusters. The rhomboid particles showed less-intense emissions related to defects compared with the other two types while also exhibiting the least intense emissions related to FX phonon replicas. This work also examined the mechanism by which nanoparticles were produced by LAL on the basis of the spectroscopic data. The information presented herein is expected to assist in the design and fabrication of semiconductor nanoparticles for future nanotechnology applications.
TL;DR: In this article , the efficacy and safety of pembrolizumab in multiple facilities were examined in a large-scale retrospective real-world data set with 167 patients with recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN).
Abstract: Background/Aim: Pembrolizumab exhibits anticancer efficacy in platinum-sensitive or platinum-unfit patients with recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN). However, no large-scale retrospective real-world data are available. This retrospective study aimed to examine the efficacy and safety of pembrolizumab in multiple facilities. Patients and Methods: Data of 167 patients with R/M SCCHN treated with pembrolizumab between December 2019 and February 2022 were analyzed. The endpoint was overall survival (OS), progression-free survival (PFS), and immune-related adverse events (irAEs). OS and PFS were analyzed comparatively with and without irAEs, and complete response (CR) or partial response (PR), and stable disease (SD) or progressive disease (PD) were compared. Results: One hundred thirty-five patients received pembrolizumab alone, whereas the others received pembrolizumab with chemotherapy. For the pembrolizumab only group, the median OS and PFS were 22.7 and 5.1 months, respectively. There were significant differences in OS and PFS between CR or PR and SD or PD (p<0.01, p<0.01, respectively). For pembrolizumab with chemotherapy, the OS was not reached and median PFS was 7.0 months. There was a significant difference in PFS between CR or PR and SD or PD (p<0.01). There was a significant difference in PFS between patients with and without irAEs (p=0.02). Conclusion: The real-world therapeutic effect of pembrolizumab for R/M SCCHN was comparable to that observed in the KEYNOTE048 trial. In addition, irAEs and best overall response were considered as prognostic factors.
TL;DR: In this article , an OER electrocatalyst for use in alkaline media is prepared by hybridising rhombohedral boron monosulfide with graphene to provide electronic conductivity.
TL;DR: In this paper , a Wolter mirror and a sample are arranged with two mounting stages, aligned with three degrees of freedom, and the sample with two degrees, for the spectroscopic mapping of a microstructure with a nano-focused beam at a soft X-ray beamline of synchrotron radiation.
Abstract: We developed a compact system for the spectroscopic mapping of a microstructure with a nano-focused beam at a soft X-ray beamline of synchrotron radiation. The experimental setup comprises a Wolter mirror and sample that are arranged with two mounting stages. The Wolter mirror is aligned with three degrees of freedom, and the sample with two degrees. The system generates a beam with an 800-nm spot and maps out a chemical distribution of non-uniform material through near-edge X-ray fine structure spectroscopy. The design and actual system are suited to experiments conducted with a nano-focused X-ray beam at beamlines of synchrotron radiation or an X-ray free-electron laser. Additionally, this technical note presents guidelines for actual experiments.
TL;DR: A multicenter, randomized controlled phase III trial was conducted on sentinel lymph node biopsy (SLNB) and elective neck dissection for T1 (depth of invasion ≥ 4 mm) and T2N0M0 oral cavity squamous cell carcinoma as discussed by the authors .
Abstract: A multicenter, randomized controlled phase III trial was conducted on sentinel lymph node biopsy (SLNB) and elective neck dissection for T1 (depth of invasion ≥ 4 mm)–T2N0M0 oral cavity squamous cell carcinoma. This study identified factors associated with poor prognosis in patients who underwent SLNB based on a subgroup analysis of this trial. We analyzed 418 sentinel lymph nodes (SLNs) from 132 patients who underwent SLNB. The metastatic SLNs were classified into three categories based on size-isolated tumor cells: < 0.2 mm, micrometastasis: ≥ 0.2 mm and < 2 mm, and macrometastasis: ≥ 2 mm. Three groups were formed based on the number of metastatic SLNs: no metastasis, 1 metastatic node, and ≥ 2 metastatic nodes. The size and number of metastatic SLNs on survival were evaluated using Cox proportional hazard models. Patients with macrometastasis and ≥ 2 metastatic SLNs had worse overall survival (OS) and disease-free survival (DFS) after adjustment for potential confounders (HR for OS: macrometastasis, 4.85; 95% CI 1.34–17.60; ≥ 2 metastatic SLN, 3.63; 95% CI 1.02–12.89; HR for DFS: macrometastasis, 2.94; 95% CI 1.16–7.44; ≥ 2 metastatic SLN, 2.97; 95% CI 1.18–7.51). In patients who underwent SLNB, a poorer prognosis was associated with macrometastasis or having ≥ 2 metastatic SLNs.
TL;DR: In this article , a measurement of the top-quark mass in the $t\bar{t}\rightarrow~\textrm{lepton}+\textm{jets}$ channel is presented, with an experimental technique which exploits semileptonic decays of $b$-hadrons produced in the topquark decay chain.
Abstract: A measurement of the top-quark mass ($m_t$) in the $t\bar{t}\rightarrow~\textrm{lepton}+\textrm{jets}$ channel is presented, with an experimental technique which exploits semileptonic decays of $b$-hadrons produced in the top-quark decay chain. The distribution of the invariant mass $m_{\ell\mu}$ of the lepton, $\ell$ (with $\ell=e,\mu$), from the $W$-boson decay and the muon, $\mu$, originating from the $b$-hadron decay is reconstructed, and a binned-template profile likelihood fit is performed to extract $m_t$. The measurement is based on data corresponding to an integrated luminosity of 36.1 fb$^{-1}$ of $\sqrt{s} = 13~\textrm{TeV}$ $pp$ collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. The measured value of the top-quark mass is $m_{t} = 174.41\pm0.39~(\textrm{stat.})\pm0.66~(\textrm{syst.})\pm0.25~(\textrm{recoil})~\textrm{GeV}$, where the third uncertainty arises from changing the PYTHIA8 parton shower gluon-recoil scheme, used in top-quark decays, to a recently developed setup.
TL;DR: In this paper , the authors developed an effective treatment method for achieving long-term stabilization of two-dimensional hydrogen boride (HB) sheets, by pre-treating the HB sheets with water and then filtering the dried product from an acetonitrile dispersion.
Abstract: Two-dimensional hydrogen boride (HB) sheets prepared via the ion-exchange reaction from magnesium diboride (MgB2) are known to possess several intriguing properties for a wide range of applications; however, previous reports have shown that the sheets prepared using this method contain small amounts of reactive components, making them unsuitable for certain applications. Therefore, developing a method for preparing HB sheets that exhibit long-term stability and do not contain reactive species is essential. In this study, we developed an effective treatment method for achieving long-term stabilization of HB sheets. We found that by pre-treating the HB sheets with water and then filtering the dried product from an acetonitrile dispersion, we could achieve excellent long-term stability over nine months. This stability was maintained even outside of a glovebox, with no H2 released by the decomposition and/or reaction. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) absorption spectroscopy measurements revealed that the sample exhibited pure HB characteristics with negatively charged boron and B-H-B and terminal B-H bonds, even after nine months of storage. Furthermore, based on thermal desorption spectroscopy (TDS) measurements, the presence of reactive species in the as-prepared HB sheets is attributed to fluctuating B-H bonds with relatively weak binding energies that can be removed using the method developed in this study.
TL;DR: In this paper , a cyclic hydrogenated boron molecule with a three-center two-electron bond at the center has been found and its electronic structure has been discussed.
Abstract: We have extensively searched for a cyclic hydrogenated boron molecule that has a three-center two-electron bond at the center. Using first-principles calculations, we discovered a stable molecule of 2:4:6:8:-2H-1,5:1,5-μH-B8H10 and propose its existence. This molecule can be regarded as a building block for sheets of topological hydrogen boride (borophane), which was recently theoretically proposed and experimentally discovered. The electronic structure of the cyclic hydrogenated boron molecule is discussed in comparison with that of cyclic hydrogenated carbon molecules.
TL;DR: The magnetic anisotropy and magnetic interactions at the interface between Fe and NiO(001) were investigated in this article , where the preferential magnetization direction of the ultrathin Fe layer grown on a NiO (001) layer changed from in-plane to a direction perpendicular to the film plane.
Abstract: The magnetic anisotropy and magnetic interactions at the interface between Fe and NiO(001) were investigated. Depending on the growth conditions of the NiO(001) layers and the post-annealing temperature, the preferential magnetization direction of the ultrathin Fe layer grown on a NiO(001) layer changed from in-plane to a direction perpendicular to the film plane. The lattice constant of the NiO(001) layers parallel to the growth direction increased with O$_2$ flow rate, while that parallel to the in-plane were locked onto the MgO(001) substrate regardless of the growth conditions of the NiO layers. Moreover, perpendicular magnetization was observed only when the NiO layer was grown with O$_2$ flow rates higher than 2.0 sccm corresponding to oxygen-rich NiO. X-ray magnetic circular dichroism measurements revealed an enhancement in anisotropic orbital magnetic moments similar to the origin of perpendicular magnetic anisotropy at the Fe/MgO(001) interface. The interfacial magnetic anisotropy energies were 0.93 and 1.02 mJ/m$^2$ at room temperature and at 100 K, respectively, indicating less temperature dependence. In contrast, the coercivity $H_c$ exhibited a significant temperature dependence. Although no signature of exchange bias or unidirectional loop shift was observed, $H_c$ was strongly dependent on the NiO layer thickness, indicating that the exchange interaction at the interface between the ferromagnetic and antiferromagnetic layers was not negligible, despite the NiO(001) being a spin-compensated surface.