Experimental Elucidation of a Cubane Water Cluster in the Hydrophobic Cavity of UiO-66.

Nanoscale water plays a pivotal role in determining the properties and functionalities of materials, and the precise control of its quantity and atomic-scale ordered structure is a focal point in nanotechnology and chemistry. Several studies have theoretically discussed the nano-ordered ice within one- or two-dimensional space and without confinement through hydrogen bonds. In particular, the water cluster has been predicted to play a significant role in biomolecules or functional nanomaterials; however, there has been little experimental evidence for their presence in hydrophobic cavities.

Atom-Selective Analyses Reveal the Structure-Directing Effect of Cs Cation on the Synthesis of Zeolites.

To understand the crystallization mechanism of zeolites, it is important to clarify the detailed role of the structure-directing agent, which is essential for the crystallization of zeolite, interacting with an amorphous aluminosilicate matrix. In this study, to reveal the structure-directing effect, the evolution of the aluminosilicate precursor which causes the nucleation of zeolite is analyzed by the comprehensive approach including atom-selective methods. The results of total and atom-selective pair distribution function analyses and X-ray absorption spectroscopy indicate that a crystalline-like coordination environment gradually forms around Cs cations.

Symmetric Breakage-Induced Semimetallic State: Polymorphism in Ruthenate Nanosheets.

Atomic arrangements and their symmetries govern the physical properties of materials, including nanosheets that are low-dimensional nanomaterials. Although they have the same composition, symmetric changes associated with atomic displacements sometimes induce unexpected physical properties. Herein, we report that symmetric breakage induces a semimetallic state in chemically exfoliated ruthenate nanosheets.

Temperature-dependent electronic structure of bixbyite α-MnO and the importance of a subtle structural change on oxygen electrocatalysis.

Bixbyite -MnO is an inexpensive Earth-abundant mineral that can be used to drive both oxygen evolution (OER) and oxygen reduction reactions (ORR) in alkaline conditions. It possesses a subtle orthorhombic cubic phase change near room temperature that suppresses Jahn-Teller distortions and presents a unique opportunity to study how atomic structure affects the electronic structure and catalytic activity at a temperature range that is easily accessible in OER/ORR experiments. Previously, we observed that heat-treated -MnO had a better performance as a bifunctional catalyst in the oxygen evolution (OER) and oxygen reduction reactions (ORR) (.

Structures and Role of the Intermediate Phases on the Crystallization of BaTiO from an Aqueous Synthesis Route.

Carbonate formation is a prevailing challenge in synthesis of BaTiO, especially through wet chemical synthesis routes. In this work, we report the phase evolution during thermal annealing of an aqueous BaTiO precursor solution, with a particular focus on the structures and role of intermediate phases forming prior to BaTiO nucleation. infrared spectroscopy, X-ray total scattering, and transmission electron microscopy were used to reveal the decomposition, pyrolysis, and crystallization reactions occurring during thermal processing.

Understanding the Hydrothermal Formation of NaNbO: Its Full Reaction Scheme and Kinetics.

Sodium niobate (NaNbO) attracts attention for its great potential in a variety of applications, for instance, due to its unique optical properties. Still, optimization of its synthetic procedures is hard due to the lack of understanding of the formation mechanism under hydrothermal conditions. Through X-ray diffraction, hydrothermal synthesis of NaNbO was observed in real time, enabling the investigation of the reaction kinetics and mechanisms with respect to temperature and NaOH concentration and the resulting effect on the product crystallite size and structure.

Controlled Growth of Sr Ba Nb O Hopper- and Cube-Shaped Nanostructures by Hydrothermal Synthesis.

Controlling the shape and size of nanostructured materials has been a topic of interest in the field of material science for decades. In this work, the ferroelectric material Sr Ba Nb O (x=0.32-0.

Lepidocrocite-Type Titanate Formation from Isostructural Prestructures under Hydrothermal Reactions: Observation by Synchrotron X-ray Total Scattering Analyses.

The formation of titanium dioxides, such as rutile and anatase, is known to proceed through the formation of a lepidocrocite-type layered structure under hydrothermal conditions, but the nucleation of this intermediate is still not understood well. Here, the nucleation of lepidocrocite-type layered titanates under hydrothermal conditions is observed by tracking the structural changes by in situ time-resolved pair distribution function analyses. We found that titanate clusters or corrugated layered prestructures having <1 nm domains with lepidocrocite-type connectivity were formed even before thermal treatment in alkaline aqueous solution.

Condensed ferric dimers for green photocatalytic synthesis of nylon precursors.

Although iron oxides have been extensively studied as photocatalysts because of their abundance and environmental compatibility, their performance is notoriously low due to factors such as low photoinduced charge-separation efficiency. Iron oxides, thus, must be modified with expensive and/or toxic materials to attain higher performances, which devalues their appeal as sustainable materials. Here, we design an iron oxide exhibiting an unprecedentedly high photocatalytic performance unrealized by previous photocatalysts such as TiO for reactions including the selective oxidation of cyclohexane to industrial nylon precursors.

Conductive Nanosized Magnéli-Phase TiO with a Core@Shell Structure.

Magnéli-phase TiO, known for its high electrical conductivity and corrosion resistance, is typically prepared by hydrogen reduction at high temperatures (∼1000 °C), leading to large particles. Nanosized TiO have been explored for application toward high specific surface area electrode materials and electrocatalyst supports; nonetheless, the particle size of TiO is still insufficient for utilization as a support. In this study, we have pursued a novel synthetic approach for nanosized TiO platelets with a length of 10-80 nm and thickness of 3-10 nm even under high-temperature conditions.

Zeolitic intralayer microchannels of magadiite, a natural layered silicate, to boost green organic synthesis.

Despite the considerable attention given to the applications of magadiite in previous research, the properties of this natural layered silicate have remained mysterious due to the lack of crystal structure information. On the other hand, no one has doubted the intercalation capability the layers. Here we succeed in determining the structure of magadiite using X-ray pair distribution functions and synchrotron powder diffractometry.

Time-resolved pair distribution function analysis of disordered materials on beamlines BL04B2 and BL08W at SPring-8.

A dedicated apparatus has been developed for studying structural changes in amorphous and disordered crystalline materials substantially in real time. The apparatus, which can be set up on beamlines BL04B2 and BL08W at SPring-8, mainly consists of a large two-dimensional flat-panel detector and high-energy X-rays, enabling total scattering measurements to be carried out for time-resolved pair distribution function (PDF) analysis in the temperature range from room temperature to 873 K at pressures of up to 20 bar. For successful time-resolved analysis, a newly developed program was used that can monitor and process two-dimensional image data simultaneously with the data collection.

Curved Fragmented Graphenic Hierarchical Architectures for Extraordinary Charging Capacities.

An approach to assemble hierarchically ordered 3D arrangements of curved graphenic nanofragments for energy storage devices is described. Assembling them into well-defined interconnected macroporous networks, followed by removal of the template, results in spherical macroporous, mesoporous, and microporous carbon microball (3MCM) architectures with controllable features spanning nanometer to micrometer length scales. These structures are ideal porous electrodes and can serve as lithium-ion battery (LIB) anodes as well as capacitive deionization (CDI) devices.

Mesoporous Semimetallic Conductors: Structural and Electronic Properties of Cobalt Phosphide Systems.

Mesoporous cobalt phosphide (meso-CoP) was prepared by the phosphorization of ordered mesoporous cobalt oxide (meso-Co O ). The electrical conductivity of meso-CoP is 37 times higher than that of nonporous CoP, and it displays semimetallic behavior with a negligibly small activation energy of 26 meV at temperatures below 296 K. Above this temperature, only materials with mesopores underwent a change in conductivity from semimetallic to semiconducting behavior.

Formation and Characterization of Hydrogen Boride Sheets Derived from MgB by Cation Exchange.

Two-dimensional (2D) materials are promising for applications in a wide range of fields because of their unique properties. Hydrogen boride sheets, a new 2D material recently predicted from theory, exhibit intriguing electronic and mechanical properties as well as hydrogen storage capacity. Here, we report the experimental realization of 2D hydrogen boride sheets with an empirical formula of HB, produced by exfoliation and complete ion-exchange between protons and magnesium cations in magnesium diboride (MgB) with an average yield of 42.

Noncrystalline Titanium Oxide Catalysts for Electrochemical Oxygen Reduction Reactions.

Titanium oxides crystals are widely used in a variety of fields, but little has been reported on the functionalities of noncrystalline intermediates formed in their structural transformation. We measured the oxygen reduction reaction activity of titanium oxide nanoparticles heat-treated for a different time and found that the activity abruptly increased at a certain time of the treatment. We analyzed their structures by using X-ray pair distribution functions with the help of high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy and ascertained that the abrupt increase in the activity corresponded to a structural transformation from a reduced lepidocrocite-type layered titanate to a disordered structure consisting of domains of brookite-like TiO octahedral linkages.

Room-Temperature Rutile TiO Nanoparticle Formation on Protonated Layered Titanate for High-Performance Heterojunction Creation.

We report a methodology for creating protonated layered titanate-rutile heterojunctions on the outer particle surface of protonated layered titanate by treating layered potassium titanate (KTiLiO) with dilute HCl and then drying it at room temperature under reduced pressure. After Pt co-catalyst loading, this protonated layered titanate/rutile composite with heterojunctions showed higher photocatalytic H evolution activity from water under simulated solar light compared to that of Pt-loaded P25, the standard photocatalyst for this reaction. The high photocatalytic activity was ascribable to enhanced photocatalytic activity of the protonated layered titanate based on an efficient charge separation at the protonated layered titanate-rutile heterojunction in addition to the sensitization effects of rutile, which absorbs light with longer wavelengths compared to those of protonated layered titanate.

Two-Dimensional Corrugated Porous Carbon-, Nitrogen-Framework/Metal Heterojunction for Efficient Multielectron Transfer Processes with Controlled Kinetics.

The material choice for efficient electrocatalysts is limited because it is necessary to be highly active as well as highly stable. One direction to solve this issue is to understand elementary steps of electrode processes and build an unconventional strategy for a conversion of inert and, therefore, stable materials into efficient catalysts. Herein, we propose a simple concept for obtaining catalysts from inert and hence stable materials by forming their heterojunctions, namely, covering inert Au with corrugated carbon-nitrogen-based two-dimensional porous frameworks.

Physical Stabilization of Pharmaceutical Glasses Based on Hydrogen Bond Reorganization under Sub-T Temperature.

Amorphous solid dispersions (ASDs) play a key role in the pharmaceutical industry through the use of high-energy amorphous state to improve solubility of pharmaceutical agents. Understanding the physical stability of pharmaceutical glasses is of great importance for their successful development. We focused on the anti-HIV agent, ritonavir (RTV), and investigated the influence of annealing at temperatures below the glass transition temperature (sub-T) on physical stability, and found that the sub-T annealing effectively stabilized RTV glasses.

Phase pure α-MnO prisms and their bifunctional electrocatalytic activity in oxygen evolution and reduction reactions.

Synthesizing manganese oxide materials with exact control of the nanoparticle shape and phase is difficult, making it challenging to understand the influence of the surface structure on electrocatalysis. Here we describe an inexpensive, low-temperature method to synthesize single-crystal orthorhombic phase α-MnO prisms bound by the {100} facets. The synthesis is the first method to use the cation bridging effect to assist in the creation of α-MnO prisms.

Observation of Quantum Confinement in Monodisperse Methylammonium Lead Halide Perovskite Nanocrystals Embedded in Mesoporous Silica.

Hybrid organic-inorganic metal halide perovskites have fascinating electronic properties and have already been implemented in various devices. Although the behavior of bulk metal halide perovskites has been widely studied, the properties of perovskite nanocrystals are less well-understood because synthesizing them is still very challenging, in part because of stability. Here we demonstrate a simple and versatile method to grow monodisperse CHNHPbBrI perovskite nanocrystals inside mesoporous silica templates.

Cyano-Bridged Trimetallic Coordination Polymer Nanoparticles and Their Thermal Decomposition into Nanoporous Spinel Ferromagnetic Oxides.

The synthesis of a novel family of cyano-bridged trimetallic coordination polymers (CPs) with various compositions and shapes has been reported by changing the compositional ratios of Fe, Co, and Ni species in the reaction system. In order to efficiently control the nucleation rate and the crystal growth, trisodium citrate dihydrate plays an important role as a chelating agent. After the obtained cyano-bridged trimetallic CPs undergo thermal treatment in air at three different temperatures (250, 350, and 450 °C), nanoporous spinel metal oxides are successfully obtained.

Ultrahigh performance supercapacitors utilizing core-shell nanoarchitectures from a metal-organic framework-derived nanoporous carbon and a conducting polymer.

Hitherto, many reports on composite materials for electrochemical applications are based on one-dimensional carbon nanotubes or two-dimensional graphene materials. However, these composite materials usually suffer from a stacking problem during electrochemical cycling. A smart nanoarchitectural design is needed for composite materials in order to overcome this problem.

Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nanoporous Carbons.

Single metal-organic frameworks (MOFs), constructed from the coordination between one-fold metal ions and organic linkers, show limited functionalities when used as precursors for nanoporous carbon materials. Herein, we propose to merge the advantages of zinc and cobalt metals ions into one single MOF crystal (i.e.

Tunable-Sized Polymeric Micelles and Their Assembly for the Preparation of Large Mesoporous Platinum Nanoparticles.

Platinum nanoparticles with continuously tunable mesoporous structures were prepared by a simple, one-step polymeric approach. By virtue of their large pore size, these structures have a high surface area that is accessible to reagents. In the synthetic method, variation of the solvent composition plays an essential role in the systematic control of pore size and particle shape.