Functionalisation of alkali-resistant nanoporous glass via Au nanoparticle decoration using alkaline impregnation: catalytic activity for CO removal.

The concerted use of nano-metal particles with catalytic functions and nanoporous materials holds promise for effective air purification and gas sensing; however, only a few studies have used porous glasses as supports for Au nanoparticles. Furthermore, Au/nanoporous glasses with activities comparable to that of Au/TiO2, which is a typical Au catalyst, have not been reported to date. This study demonstrates that a nanoporous glass, which is highly acid- and alkali-resistant and chemically stable, can be decorated with Au nanoparticles using an alkali impregnation method. The resulting composite exhibits high catalytic activity in CO oxidation. The catalysts reported herein are as active as Au/TiO2 catalysts per active site. Further optimisation of the pore properties of the glass and sizes of the Au nanoparticles is expected to result in excellent catalytic systems for CO removal and sensing.

Fluoride Ion in Alcohols: Isopropanol vs Hexafluoroisopropanol.

The utility of alcohol as a hydrogen bonding donor is considered a providential avenue for moderating the high basicity and reactivity of the fluoride ion, typically used with large cations. However, the practicality of alcohol-fluoride systems in reactions is hampered by the limited understanding of the pertinent interactions between the OH group and F-. Therefore, this study comparatively investigates the thermal, structural, and physical properties of the CsF-2-propanol and CsF-1,1,1,3,3,3-hexafluoro-2-propanol systems to explicate the effects of the fluoroalkyl group on the interaction of alcohols and F-. The two systems exhibit vastly different phase diagrams despite the similar saturated concentrations. A combination of spectroscopic analyses, alcohol activity coefficient measurements, and theoretical calculations reveal the fluorinated alcohol system harbors the stronger OH···F- interactions between the two systems. The diffusion coefficient and ionic conductivity measurements attribute the present results to disparate states of ion association in the two systems.

Nickel Carbide Nanoparticle Catalyst for Selective Hydrogenation of Nitriles to Primary Amines.

Despite its unique physicochemical properties, the catalytic application of nickel carbide (Ni3 C) in organic synthesis is rare. In this study, we report well-defined nanocrystalline Ni3 C (nano-Ni3 C) as a highly active catalyst for the selective hydrogenation of nitriles to primary amines. The activity of the aluminum-oxide-supported nano-Ni3 C (nano-Ni3 C/Al2 O3 ) catalyst surpasses that of Ni nanoparticles. Various aromatic and aliphatic nitriles and dinitriles were successfully converted to the corresponding primary amines under mild conditions (1 bar H2 pressure). Furthermore, the nano-Ni3 C/Al2 O3 catalyst was reusable and applicable to gram-scale experiments. Density functional theory calculations suggest the formation of polar hydrogen species on the nano-Ni3 C surface, which were attributed to the high activity of nano-Ni3 C towards nitrile hydrogenation. This study demonstrates the utility of metal carbides as a new class of catalysts for liquid-phase organic reactions.

Issues on DFT+U calculations of organic diradicals.

The diradical state is an important electronic state for understanding molecular functions and should be elucidated for the in silico design of functional molecules and their application to molecular devices. The density functional theory calculation with plane-wave basis and correction of the on-site Coulomb parameter U (DFT+U/plane-wave calculation) is a good candidate of high-throughput calculations of diradical-band interactions. However, it has not been investigated in detail to what extent the DFT+U/plane-wave calculation can be used to calculate organic diradicals with a high degree of accuracy. In the present study, using typical organic diradical molecules (bisphenalenyl molecules) as model systems, the discrepancy in the optimum U values between the two electronic states (open-shell singlet and triplet) that compose the diradical state is detected. The calculated results show that the reason for this U value discrepancy is the difference in electronic delocalisation due to π-conjugation between the open-shell singlet and triplet states, and that the effect of U discrepancy becomes large as diradical character decreases. This indicates that it is necessary to investigate the U value discrepancy with reference to the calculated results by more accurate methods or to experimental values when calculating organic diradicals with low diradical character. For this investigation, the local magnetic moments, unpaired beta electron numbers, and effective magnetic exchange integral values can be used as reference values. For the effective magnetic exchange integral values, the effects of U discrepancy are partially cancelled out. However, because the effects may not be completely offset, care should be taken when using the effective magnetic exchange integral value as a reference. Furthermore, a comparison of DFT+U and hybrid-DFT calculations shows that the DFT+U underestimates the HOMO-LUMO gap of bisphenalenyls, although a qualitative discussion of the gap is possible.

Model calculations for the prediction of the diradical character of physisorbed molecules: p-benzyne/MgO and p-benzyne/SrO.

The analysis of the diradical state of functional open-shell molecules is important for understanding their physical properties and chemical reactivity. The diradical character is an important factor in the functional elucidation and design of open-shell molecules. In recent years, attempts have been made to immobilise functional open-shell molecules on surfaces to form devices. However, the influence of surface interactions on the diradical state remains unclear. In this study, the physisorption structures of p-benzyne, which is a typical diradical molecule, on MgO(001) and SrO(001) surfaces are used as models to investigate how the diradical character is affected by physisorption. This is done using approximate spin-projected density functional theory calculations with dispersion correction and plane-wave basis (AP-DFT-D3/plane-wave calculations). The diradical character change (Δy) due to adsorption can be categorised into three factors, namely the change due to the distortion of the diradical molecule (Δydis), the interaction between neighbouring diradical molecules (Δycoh), and molecule-surface interactions (Δysurf). In all the calculated models, physisorption reduced the diradical character (Δy < 0), and the contribution of Δysurf was the largest among the three factors. The calculated results show that adsorption induces electron delocalisation to π-conjugated orbitals and intramolecular charge polarisation, both of which contribute to reducing the occupancy of singly occupied molecular orbitals. This indicates that the diradical character of p-benzyne is reduced by the stabilisation of the resonance structures. Furthermore, geometry optimisation of the surfaces shows that the chemical-soft surface (SrO) varies the diradical character more significantly than the chemical-hard surface (MgO). This study shows that the open-shell electronic state and stack structure of diradical molecules can be controlled through the analysis of the surface diradical state.

Elucidation of the mechanism of melamine adsorption on Pt(111) surface via density functional theory calculations.

The oxygen reduction reaction (ORR) activity of Pt catalysts in polymer electrolyte fuel cells (PEFCs) should be enhanced to reduce Pt usage. The adsorption of heteroaromatic ring compounds such as melamine on the Pt surface can enhance its catalytic activity. However, melamine adsorption on Pt and the consequent ORR enhancement mechanism remain unclear. In this study, we performed density functional theory calculations to determine the adsorption structures of melamine/Pt(111). Melamine was coordinated to Pt via two N lone pairs on NH2 and N- in the triazine ring, resulting in a chemisorption structure with slight electron transfer. Four types of adsorption structures were identified: three-point adsorption (two amino groups and a triazine ring: Type A), two-point adsorption (one amino group and a triazine ring: Type B), two-point adsorption (two amino groups: Type C), and one-point adsorption (one amino group: Type D). The most stable structure was Type B. However, multiple intermediate structures were formed owing to the conformational changes from the most stable to other stable adsorption structures. The resonance structures of the adsorbed melamine stabilise the adsorption, as increased resonance allows for more electron delocalisation. In addition, the lone-pair orbital of the amino group in the adsorbed melamine acquires the characteristics of an sp3 hybrid orbital, which prevents horizontal adsorption on the Pt surface. We believe that understanding these adsorption mechanisms will help in the molecular design of organic molecule-decorated Pt catalysts and will lead to the reduction of Pt usage in PEFCs.

HTLV-1 bZIP factor impairs DNA mismatch repair system.

Adult T-cell leukemia (ATL) is a peripheral T-cell malignancy caused by human T-cell leukemia virus type 1 (HTLV-1). Microsatellite instability (MSI) has been observed in ATL cells. Although MSI results from impaired mismatch repair (MMR) pathway, no null mutations in the genes encoding MMR factors are detectable in ATL cells. Thus, it is unclear whether or not impairment of MMR causes the MSI in ATL cells. HTLV-1 bZIP factor (HBZ) protein interacts with numerous host transcription factors and significantly contributes to disease pathogenesis and progression. Here we investigated the effect of HBZ on MMR in normal cells. The ectopic expression of HBZ in MMR-proficient cells induced MSI, and also suppressed the expression of several MMR factors. We then hypothesized that the HBZ compromises MMR by interfering with a transcription factor, nuclear respiratory factor 1 (NRF-1), and identified the consensus NRF-1 binding site at the promoter of the gene encoding MutS homologue 2 (MSH2), an essential MMR factor. The luciferase reporter assay revealed that NRF-1 overexpression enhanced MSH2 promoter activity, while co-expression of HBZ reversed this enhancement. These results supported the idea that HBZ suppresses the transcription of MSH2 by inhibiting NRF-1. Our data demonstrate that HBZ causes impaired MMR, and may imply a novel oncogenesis driven by HTLV-1.

Mechanism of Reductive Fluorination by PTFE-Decomposition Fluorocarbon Gases for WO3.

Reductive fluorination, which entails the substitution of O2- from oxide compounds with F- from fluoropolymers, is considered a practical approach for preparing transition-metal oxyfluorides. However, the current understanding of the fundamental reaction paths remains limited due to the analytical complexities posed by high-temperature reactions in glassware. Therefore, to expand this knowledgebase, this study investigates the reaction mechanisms behind the reductive fluorination of WO3 using polytetrafluoroethylene (PTFE) in an Ni reactor. Here, we explore varied reaction conditions (temperature, duration, and F/W ratio) to suppress the formation of carbon byproducts, minimize the dissipation of fluorine-containing tungsten (VI) compounds, and achieve a high fluorine content. The gas-solid reaction paths are analyzed using infrared spectroscopy, which revealed tetrafluoroethylene (C2F4), hexafluoropropene (C3F6), and iso-octafluoroisobutene (i-C4F8) to be the reactive components in the PTFE-decomposition gas during the reactions with WO3 at 500 °C. CO2 and CO are further identified as gaseous byproducts of the reaction evincing that the reaction is prompted by difluorocarbene (:CF2) formed after the cleavage of C═C bonds in i-C4F8, C3F6, and C2F4 upon contact with the WO3 surface. The solid-solid reaction path is established through a reaction between WO3 and WO3-xFx where solid-state diffusion of O2- and F- is discerned at 500 °C.

Honeycomb-Layered Oxides With Silver Atom Bilayers and Emergence of Non-Abelian SU(2) Interactions.

Honeycomb-layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next-generation energy storage applications. Herein, global honeycomb-layered oxide compositions, Ag2 M2 TeO6 ( M = Ni , Mg , etc $M = \rm Ni, Mg, etc$ .) exhibiting Ag $\rm Ag$ atom bilayers with sub-valent states within Ag-rich crystalline domains of Ag6 M2 TeO6 and Ag $\rm Ag$ -deficient domains of Ag 2 - x Ni 2 TeO 6 ${\rm Ag}_{2 - x}\rm Ni_2TeO_6$ ( 0 < x < 2 $0 < x < 2$ ). The Ag $\rm Ag$ -rich material characterized by aberration-corrected transmission electron microscopy reveals local atomic structural disorders characterized by aperiodic stacking and incoherency in the bilayer arrangement of Ag $\rm Ag$ atoms. Meanwhile, the global material not only displays high ionic conductivity but also manifests oxygen-hole electrochemistry during silver-ion extraction. Within the Ag $\rm Ag$ -rich domains, the bilayered structure, argentophilic interactions therein and the expected Ag $\rm Ag$ sub-valent states ( 1 / 2 + , 2 / 3 + $1/2+, 2/3+$ , etc.) are theoretically understood via spontaneous symmetry breaking of SU(2)× U(1) gauge symmetry interactions amongst 3 degenerate mass-less chiral fermion states, justified by electron occupancy of silver 4 d z 2 $4d_{z^2}$ and 5s orbitals on a bifurcated honeycomb lattice. This implies that bilayered frameworks have research applications that go beyond the confines of energy storage.

Properties of spinel-type Ti-Li-M composite oxides (M = Li, Na, Cu, and Ag) predicted by density functional theory.

Spinel-type titanate is an important material already being used as a stable anode for Li-ion batteries. In addition, spinel titanate shows superconducting properties upon tuning the amount of Li+-doping; hence, research on magnetic and superconducting materials has been conducted. However, it is believed that only the tiny Li+ monocation can occupy the 8a sites due to its small voids and the charge valence with Ti cations. In recent years, new spinel-type titanium oxides have been discovered, in which 8a sites are occupied by Na+ or Ag+. Although the application of these new compounds to catalyst and electrode materials has been attempted, the effect of 8a site monocations on the physical properties of spinel-type titanium oxide is unclear. In this study, to systematise the effects of 8a-site monocations on the Ti-O framework, theoretical calculations based on density functional theory (DFT), such as GGA, GGA+U, and hybrid-DFT, were performed for the electronic structures and geometric stabilities of four spinel-titanium oxides: LTO (8a sites occupied by Li+), NTO (8a sites occupied by Na+), CTO (8a sites occupied by Cu+), and ATO (8a sites occupied by Ag+). Furthermore, to verify the effect of the partial substitution, Li+, Na+, Cu+, and Ag+ doping of LTO, NTO, CTO, and ATO was also investigated. Throughout these calculations, the performance of spinel-type titanates can be categorised by (1) the magnitude of O-displacement and (2) the orbital correlation between the Ti-O framework and the 8a site cations. By appropriately selecting cations, the spinel titanates can be applied to battery materials, catalysts, optical materials, photocatalysts, and precursors to these materials.

Refractory immune thrombocytopenic purpura associated with IgM monoclonal gammopathy of undetermined significance: Successful treatment with tirabrutinib plus conventional therapies.

When immune thrombocytopenia (ITP) is secondary to malignant diseases, chemotherapy is expected to improve the platelet count (PC) as well. Herein, we report a case of a 72-year-old man with ITP refractory to standard therapies. IgM monoclonal gammopathy of undetermined significance (MGUS) was determined as an underlying disease. After bendamustine and rituximab (BR) therapy was found inadequately effective, tirabrutinib, a novel Bruton's tyrosine kinase inhibitor, was initiated, and the PC normalised subsequently. Surveillance of underlying diseases with which effective therapies are available may help manage refractory ITP, and IgM-MGUS is potentially a targetable underlying disease with this newly available drug.

Stability of Zirconium-Substituted Face-Centered Cubic Yttrium Hydride.

The stability of a zirconium (Zr)-substituted face-centered cubic (FCC) yttrium (Y) hydride (Y1-xZrx hydride) phase was investigated experimentally and theoretically. Two possible sites for hydrogen atoms exist in the FCC structure, namely, T- and O-sites, where hydrogen is present at the center of the tetrahedron and the octahedron composed of Y and/or Zr metals. The P-C isotherms revealed that the hydrogen content per metal (H/M) with 33% Zr-substituted YH3-δ was 2.2-2.3, which was lower than the expected value calculated from the starting composition of YH3-33% ZrH2 (Y0.67Zr0.33H2.67, H/M = 2.67). Hydrogen at the O-site in Y1-xZrx hydride mainly reacted during hydrogen desorption/absorption. On the basis of theoretical analyses, the hydrogen atoms do not occupy the center of the octahedron, when at least two of the six vertices of the octahedron were composed of Zr. The O-sites, where more than two Zr atoms coordinate, nonlinearly increased with the Zr content, and when the Zr content was >50%, almost no hydrogen atoms occupy the O-sites. The theoretical discussion supported the experimental results, and the Zr substitution was confirmed to reduce the occupancy of H at the O-site in the FCC YH3 significantly.

Can we enhance diradical character using interaction with stoichiometric surfaces of ionic oxides? A theoretical investigation using chemical indices.

Chemical indices are effective tools for examining the functions and reactivities of stable radical species. In this study, we formulated an approximation to estimate chemical indices using electron density. Theoretical investigations using the developed scheme revealed that surface interactions can tune chemical indices and that the diradical character was enhanced by weak adsorption onto ionic solids with charge-dipole interactions.

Boosting the electrocatalytic activity of Pd/C by Cu alloying: Insight on Pd/Cu composition and reaction pathway.

Tuning composition of Pd-based bimetallic electrocatalysts of high stability and durability is of great importance in energy-related reactions. This study reports the remarkable electrocatalytic performance of carbon-supported bimetallic Pd-Cu alloy nanoparticles (NPs) towards formic acid oxidation (FAO) and oxygen reduction reaction (ORR). Among various bimetallic compositions, Pd3Cu/C alloy NPs exhibits the best FAO and ORR activity. During FAO reaction, Pd3Cu/C alloy NPs exhibits a peak with a current density of 28.33 mA cm-2 and a potential of 0.2 V (vs. Ag/AgCl) which is higher than that of the other PdCu compositions and standard 20 wt% Pd/C catalyst. Meanwhile, the onset potential (-0.09 V), half-wave potential (-0.18 V), limiting current density at 1600 rpm (-4.9 mA cm-2) and Tafel slope (64 mV dec-1) values of Pd3Cu/C alloy NPs validate its superiority over the conventional 20 wt% Pt/C catalyst for ORR. Experimental and DFT studies have confirmed that the enhanced activity can be attributed to the electronic effect that arises after Cu alloying which causes a downshift of Pd d-band center and structural effect that produces highly dispersed NPs over the carbon matrix with high electrochemically active surface area.

Realizing the Single-Phase Spinel-Type Sodium Titanium Oxide with the Li4Ti5O12-like Structure for Building Stable Sodium-Ion Batteries.

Sodium titanium oxide with a spinel-type structure is suitable for the stable sodium-intercalation host for the negative electrode of sodium-ion batteries, such as the spinel-type lithium titanium oxide (Li4Ti5O12, LTO) material for lithium-ion batteries. Recently, this has been partly discovered as the Na3LiTi5O12 (NTO) phase in the LTO particle. However, the single-phase NTO material has never been obtained, preventing accurate material characterizations and applications. Here, we successfully realized the NTO material with the single-phase by the chemical sodium insertion-extraction process. The chemical sodium-inserted LTO material is well converted to the pure NTO phase in the single particle level, via following chemical oxidation by water. The purified material was about 97 mol % of NTO as the single-phase spinel structure with a = 8.746 Å. The basic lattice framework of the prepared NTO was confirmed to be the same as that of the LTO. The single-phase NTO electrode shows 0.8 V versus Na+/Na of the Na-insertion and extraction potential, and 99.4% of Na-insertion capacity with 99.7% of Coulombic efficiency during 200 cycles of the Na-ion half-cell experiment. Further, the Na2Fe2(SO4)3/NTO full-cell shows 3 V-class stable charge-discharge character during 100 cycles. This excellent stability of Na-insertion and extraction properties of single-phase NTO extends the range of constructing safe and stable high-voltage oxide-based sodium-ion battery cells for practical use.

How does the Li-distribution in the 16d sites determine the stability of A3(Li,Ti5)O12 (A = Li and Na)?

Li3(Li,Ti5)O12 (LTO) is a stable and safe negative electrode material for Li-ion batteries, and its Na substitute Na3(Li,Ti5)O12 (NTO) is a counterpart for the Na-ion battery. In LTO and NTO, a sixth of the Ti-sites (16d) in the spinel framework are replaced by Li: Li mixing in the 16d sites. For conducting theoretical studies on these materials, e.g., density functional theory (DFT) calculations, one has to confront the astronomical number of combinations of Li distribution in 16d sites to construct model structures, of which the size is sufficiently large to represent the bulk material properties. Only a limited number of models, whose structures are a priori specified by "researcher intuition," have been examined thus far, and how Li-mixing determines the material stability has yet to be clarified. Herein, we statistically analyzed the DFT total energy of more than 2 × 104 model structures of LTO and NTO that were extracted from the 4 × 108 possible combinations of Li-mixing with computer-aided symmetry analysis and an automated model building system. The local energy analysis further revealed the local stability/instability of each structure. We found that LTO and NTO stability can be well explained by the apparent coulombic repulsion between Li+ in the 16d sites as if they were placed in a matrix of dielectric constants of 1.92 and 2.04 for LTO and NTO, respectively. That is, the sum of the inverse of the Li-Li distance (S) serves as a good descriptor in predicting the stability of these materials. The extent to which the O2- anions are displaced from the Wyckoff position (32e) is considered to differentiate NTO from LTO. However, the electronic structure of NTO does not significantly differ from that of LTO unless S exceeds a certain limit. These results suggest that the spinel framework tolerates the structural instability and variety to some extent, which is important in constructing a spinel structure with the mixing of other cations, thereby replacing the rare element Li.

Monte-Carlo simulation combined with density functional theory to investigate the equilibrium thermodynamics of electrode materials: lithium titanates as model compounds.

By using lithium titanate (LTO) as a model electrode material, the present study proposes a method to describe its equilibrium thermodynamics based on the Monte-Carlo simulation (MC), for which the energetic parameters are determined by the density functional theory (DFT). The electrochemical potential profile is simulated by a simple topological model which consists only of three parameters representing the Li site energies; namely, the potential energy of the 8a site (ε8a), the difference in the site energy between the 8a and 16c sites (Δε) and the repulsion between two Li atoms situated at the adjacent 8a and 16c sites (J). Parameter physics by the MC revealed that the term Δε plays a decisive role, with a collateral effect from J, for characterizing the shape of the potential profile whereas the term ε8a determines its position along the electrochemical potential. For instance, if Δε exceeds the thermal energy at the temperature under consideration, i.e., if Δε > 3kT, the first-order phase transition takes place during which two phases coexist, resulting in a plateau region in the potential profile. On the other hand, if Δε < 3kT, the lithiation of LTO is viewed as a phenomenon above the critical point, above which the material is in a homogeneous uniphasic state. A multiple regression analysis of a set of the total energy calculated by DFT allows us to determine these energetic terms. The MC simulation with the determined parameters well reproduces the shape and position of the experimental potential profile of LTO. Since the determined value, Δε/eV ∼ 0.4, far exceeds the thermal energy at ambient temperature, the potential plateau of LTO is explained by the first-order phase transition as long as the equilibrium state is concerned.

Extent of Spin Contamination Errors in DFT/Plane-wave Calculation of Surfaces: A Case of Au Atom Aggregation on a MgO Surface.

The aggregation of Au atoms onto a Au dimer (Au2) on a MgO (001) surface was calculated by restricted (spin-un-polarized) and unrestricted (spin-polarized) density functional theory calculations with a plane-wave basis and the approximate spin projection (AP) method. The unrestricted calculations included spin contamination errors of 0.0⁻0.1 eV, and the errors were removed using the AP method. The potential energy curves for the aggregation reaction estimated by the restricted and unrestricted calculations were different owing to the estimation of the open-shell structure by the unrestricted calculations. These results show the importance of the open-shell structure and correction of the spin contamination error for the calculation of small-cluster-aggregations and molecule dimerization on surfaces.

Theoretical study of correlations between the coordination structures and catalytic activities in polymer-stabilized au nanocluster catalysts.

Au nanoclusters (Au NCs) stabilized by poly(N-vinyl-2-pyrrolidone) and poly(allylamine), abbreviated to Au:PVP and Au:PAA, catalyze the aerobic oxidation of p-hydroxybenzyl alcohols, but the catalytic activity of Au:PVP is much higher than that of Au:PAA. To elucidate the correlations between the catalytic activities and coordination structures of the stabilizing polymer, the substrate accessibility on Au NCs was estimated by density functional theory (DFT) and molecular dynamics (MD) calculations. For MD simulations, we applied a systematic method to optimize the temperature parameters in temperature replica exchange molecular dynamics (T-REMD), and the coordination structures were comprehensively classified by multivariate analysis. The results show that the number of open active sites on the Au NCs is a good index for predicting the catalytic activities. © 2018 Wiley Periodicals, Inc.