Molybdenum sulfides are very attractive noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER) from water. The atomic structure and identity of the catalytically active sites ...have been well established for crystalline molybdenum disulfide (c-MoS2) but not for amorphous molybdenum sulfide (a-MoSx), which exhibits significantly higher HER activity compared to its crystalline counterpart. Here we show that HER-active a-MoSx, prepared either as nanoparticles or as films, is a molecular-based coordination polymer consisting of discrete Mo3S13(2-) building blocks. Of the three terminal disulfide (S2(2-)) ligands within these clusters, two are shared to form the polymer chain. The third one remains free and generates molybdenum hydride moieties as the active site under H2 evolution conditions. Such a molecular structure therefore provides a basis for revisiting the mechanism of a-MoSx catalytic activity, as well as explaining some of its special properties such as reductive activation and corrosion. Our findings open up new avenues for the rational optimization of this HER electrocatalyst as an alternative to platinum.
Direct observation of demagnesiated structure of MgMn2O4 spinel oxides at atomic scale has been achieved using spherical aberration-corrected scanning transmission electron microscopy (STEM) with ...high-angle annular-dark-field (HAADF) and annular-bright-field (ABF) techniques. Upon the Mg ions extraction from MgMn2O4 spinel oxides, structural transition from cubic to tetragonal phases was observed. The phase transition is a result of Mn octahedral distortion due to cooperative Jahn–Teller distortion of six-coordinate MnIII (t2g3–eg1). On the basis of HAADF/ABF micrographs and electron energy-loss spectrometer (EELS), it is suggested that Mn3+/Mn4+ and/or Mn3+/Mn5+ redox couples play a crucial role in the first electrochemical Mg deintercalation. This is the first report on observation of cubic-tetragonal phase transition in charged spinel MgMn2O4 which shed new insight into the magnesium storage mechanism in this important cathode material for Mg-ion batteries.
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•Direct observation of demagnesiated structure of MgMn2O4 spinel oxides•Structural transition from cubic to tetragonal phases was observed.•The phase transition is due to cooperative Jahn–Teller distortion.
Exploring novel electrode materials is critical for the development of a next-generation rechargeable magnesium battery with high volumetric capacity. Here, we showed that a distinct amorphous ...molybdenum sulfide, being a coordination polymer of disulfide-bridged (Mo3S11) clusters, has great potential as a rechargeable magnesium battery cathode. This material provided good reversible capacity, attributed to its unique structure with high flexibility and capability of deformation upon Mg insertion. Free-terminal disulfide moiety may act as the active site for reversible insertion and extraction of magnesium.
Mono- and few-layer exfoliated MoSe2 with great variety of vacancies and edge defects which act favorably as catalytic centers for the H2 evolution, showed interesting catalytic activity for the HER ...in water.
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•Single- to few-layers MoSe2 nanosheets were obtained by exfoliation.•Great variety of vacancies and edge defects in MoSe2 nanosheets.•MoSe2 nanosheets showed attractive catalytic performance.
Single- to few-layers MoSe2 nanosheets were obtained from bulk MoSe2 by a supercritical fluid exfoliation. High angle annular dark field (HAADF) imaging showed the presence of a great variety of vacancies and edge defects within the exfoliated MoSe2 nanosheets. Thanks to these defects, the exfoliated MoSe2 nanosheets showed attractive catalytic performance and robustness for the hydrogen evolution reaction in water. The best electrode made of these nanosheets required 300 mV overpotential to generate a catalytic current of 10 mA/cm2 and showed a Tafel slop of 90 mV/s. The catalytic performance was further enhanced by twice when the MoSe2 nanosheets catalyst was conditioned at a mild oxidative potential, e.g.+0.73 V vs. RHE. The mild oxidation treatment was proposed to create novel Se-vacancy and Se2-vacancy while an oxidation treatment at higher potential, e.g. +1.23 V vs. RHE, completely oxidized MoSe2 into inactive MoO3. As a consequence, the later caused a rapid degradation of catalytic performance.
Lithium-ion battery that consists of a cathode made of (Mo3S11)n polymer and an anode of Li metal exhibits a high gravimetric-capacity, 673.3 mAh g−1. A flexible structure of the (Mo3S11) n polymer ...enables consecutive redox reactions of the S22− dimer and the Mo atoms. According to X-ray absorption near-edge spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy, the chemical bonds of Mo–S and S–S in the polymer elongate by accepting electrons up to 16, while the Mo–Mo bond does not change much during the redox reactions. Although the polymer cathode is put in a solid-state electrolyte, the S22− dimer that is redoxed by the reaction of S22− + 2e−→ 2S2− forms Li–S–Li bonds, which is an origin of the high capacity of the battery. The redox reactions in the (LixMo3S11)n polymer cathode is theoretically confirmed by first principles calculation.
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The ultrathin two-dimensional nanosheets of layered transition-metal dichalcogenides (TMDs) have attracted great interest as an important class of materials for fundamental research and technological ...applications. Solution-phase processes are highly desirable to produce a large amount of TMD nanosheets for applications in energy conversion and energy storage such as catalysis, electronics, rechargeable batteries, and capacitors. Here, we report a rapid exfoliation by supercritical fluid processing for the production of MoS2 and MoSe2 nanosheets. Atomic-resolution high-angle annular dark-field imaging reveals high-quality exfoliated MoS2 and MoSe2 nanosheets with hexagonal structures, which retain their 2H stacking sequence. The obtained nanosheets were tested for their electrochemical performance in a hybrid Mg–Li-ion battery as a proof of functionality. The MoS2 and MoSe2 nanosheets exhibited the specific capacities of 81 and 55 mA h g–1, respectively, at a current rate of 20 mA g–1.
Calcitonin (CT) is a marker for both initial diagnosis and monitoring of patients with residual or recurrent medullary thyroid carcinoma (MTC). In Japan, serum CT had been measured by ...radioimmunoassay (RIA) until recently. Electrochemiluminescence immunoassay (ECLIA) became commercially available in 2014, and this technique is now the only method used to examine CT concentration. The purposes of this study were to investigate the correlations between the CT concentration measured with ECLIA (ECLIA-CT) and RIA (RIA-CT) and to explore the clinical characteristics of patients with elevated ECLIA-CT. CT concentrations of 348 sera samples from 334 patients with various thyroid disorders including nine MTC were measured using both assays. The correlation analysis revealed an excellent correlation between ECLIA-CT and RIA-CT among the cases with CT level >150 pg/mL by both assays (rs = 0.991, p < 0.001). However, 63% of all samples exhibited undetectable ECLIA-CT, while their RIA-CTs were measured between 15 and 152 pg/mL. The ECLIA-CTs in all patients who underwent total thyroidectomy for non-MTC showed low concentrations. High ECLIA-CT was observed in patients with MTC or pancreas neuroendocrine tumor. ECLIA-CT was also increased in 14 other male patients with non-MTC, including four with renal failure. Multivariate logistic regression analysis showed that male sex, negative TgAb, and lower estimated glomerular filtration rate were independent factors to predict detectable ECLIA-CT (≥0.500 pg/mL). These results indicate that ECLIA-CT correlates well with RIA-CT in higher range and is affected by sex, TgAb, and renal function.
•We evaluated the anti-psoriatic potential of our novel RORγt inhibitor, S18-000003.•Topical S18-000003 showed strong efficacy in a mouse model of psoriasis.•All IL-17-producing cell subsets were ...suppressed in S18-000003-treated skin.•Topical S18-000003 could have a low risk of thymic lymphoma.
Retinoic acid receptor-related orphan receptor gamma t (RORγt) has critical roles in the development, maintenance and function of interleukin (IL)-17-producing cells and is a highly attractive target for the treatment of IL-17-mediated autoimmune disease, particularly psoriasis. On the other hand, RORγt is also critical for controlling apoptosis during thymopoiesis, and genetic RORγt ablation or systematic RORγt inhibition cause progressive thymic aberrations leading to T cell lymphomas.
We investigated whether topical administration of our novel RORγt inhibitor, S18-000003 has therapeutic potential for psoriasis with low risk of thymic aberrations.
We evaluated the effect of topical S18-000003 on psoriasis-like skin inflammation and influence on the thymus in a 12-O-tetradecanoylphorbol-13-acetate-induced K14.Stat3C mouse psoriasis model.
S18-000003 markedly inhibited the development of psoriatic skin inflammation via suppression of the IL-17 pathway. In the skin, S18-000003 suppressed all subsets of IL-17-producing cells that we previously identified in this psoriasis model: Th17 cells, Tc17 cells, dermal γδ T cells, TCR− cells that probably included innate lymphoid cells, and CD4−CD8− double-negative αβ T cells. Notably, neither reduction of CD4+CD8+ double-positive thymocytes nor dysregulation of cell cycling was observed in S18-000003-treated mice, even at a high dose.
Our topically administered RORγt inhibitor is a potential therapeutic agent for psoriasis with low risk of thymic lymphoma.
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