Search

Structured water is ubiquitous but not fully understood in confinement. Here authors show that the structure of water is sensitive to the configuration of ions in the nanoconfinement and governs ion storage in layered materials.

Hollandite-type crystals have unique and interesting physical and chemical properties. Here, we report the flux growth of hollandite-type single-crystalline potassium ferrotitanate (KFTO) with faceted surface features from a KCl flux. We varied the flux growth conditions, including the kind of flux, holding temperature, and solute concentration for growing faceted crystallites. KCl was found to be the best flux to grow the single-crystalline KFTO particles, while heating at or above 900°C was needed to yield the KFTO single crystals. The crystal growth was only weakly dependent on the solute concentration. Next, we characterized the grown single crystals and discussed the manner of their growth from the KCl flux. TEM images with clear electron diffraction spots indicated that the KFTO crystals grew along the direction to form microrods ~10 μm in size. DFT calculation results indicated that the surface energy of the (100) face is lower than that of the (001) face. Based on these characterization results, we proposed a possible growth mechanism of the KFTO crystals.

The β-Li2TiO3 crystal is an important material in several energy-related applications, and the control of its morphology and exposed facets is an important issue. Herein, we comprehensively studied the flux growth of β-Li2TiO3 crystals under different conditions and demonstrated the efficient anisotropic growth of {001}-faceted β-Li2TiO3 single crystals from the Na2SO4 flux. By examining the effects of the cation and anion in the alkali metal salt-based flux, we found that Na2SO4 flux is best for growing large, faceted β-Li2TiO3 crystals. In this flux at 1000 °C, the optimal solute concentration is 20 mol % for growing large (∼15.0 μm in lateral size), platy, and faceted β-Li2TiO3 crystals. Observations from varying the holding time and cooling rate indicated that these crystals were anisotropically grown. Transmission electron microscopy images with clear electron diffraction spots revealed that the flux-grown platy β-Li2TiO3 crystals are single crystalline solids with the {001} plane being the dominant facet. This anisotropic crystal growth could be attributed to the concerted effects of the preferential attachment of sodium cations on the {001} faces, and efficient dissolution of β-Li2TiO3 crystals as well as the solvation of the resulting O2- ions in the sulfate anion-based flux. [ABSTRACT FROM AUTHOR]

Selective lithium uptake from seawater and lake brine is an important challenge in energy and environmental science. H1.6Mn1.6O4 with pseudospinel-type structure is a highly selective adsorbent for Li ions, but it is difficult to prepare large, highly crystalline H1.6Mn1.6O4 crystals with porous structure due to its thermodynamic metastability. Herein we demonstrate simple chemical processes that transform flux-grown, idiomorphic orthorhombic LiMnO2 (o-LiMnO2) cuboids of micrometer size into hierarchically structured H1.6Mn1.6O4 rods. We have optimized the flux growth conditions such as the Mn source, holding temperature, and solute concentration in order to yield large, single-phase o-LiMnO2 particles. The use of MnO under very low solute concentration (1 mol %) and high temperature (1000 °C) is critical to obtaining the single-phase, idiomorphic o-LiMnO2 cuboids. The metastability of o-LiMnO2 is confirmed by ab initio density functional theory calculation in comparison with other lithium manganates such as LiMn2O4 and Li2MnO3. The successive calcination and acid treatment allow the transformation of o-LiMnO2 into H1.6Mn1.6O4 rods with porous structure. The resultant H1.6Mn1.6O4 shows high Li+ adsorption capacity (~5.6 mmol g-1), high Li+/Na+ selectivity, and good durability compared with existing H1.6Mn1.6O4 adsorbents. [ABSTRACT FROM AUTHOR]

Copper-indium-gallium-sulfide-selenide (CIGSSe) is used in photovoltaic cells and photocathodes, because of its tunable optoelectronic properties, but the fabrication of CIGSSe samples usually requires a multistage process under vacuum. Herein we used a flux growth technique for the sulfide system and achieved efficient flux growth of idiomorphic copper-indium-sulfide CuInS2 crystals of size ∼5 μm from a NaCl-InCl3 flux under mild conditions at ambient pressures. We first examined the flux growth conditions such as holding temperature, solute concentration, and holding time for growing highly crystalline CuInS2 crystals. A moderate holding temperature (∼550 °C) and high solute concentration (∼70 mol %) yielded idiomorphic pure CuInS2 crystals. High-resolution transmission electron microscopy showed clear electron diffraction spots, indicating that the resultant CuInS2 crystals had a highly crystalline, intrinsic tetragonal crystal structure. Thermogravimetry-differential thermal analysis showed that the CuInS2 crystals grew efficiently during flux evaporation at 550 °C, at which the flux evaporation degree reached ∼81%. The CuInS2 crystal growth mode is discussed based on the characterization results. [ABSTRACT FROM AUTHOR]

FeSe-based intercalates are regarded as promising candidates for high-critical temperature (Tc) superconductors. Here we present new Na- and Sr-intercalated FeSe superconductors with embedded linear diamines (H2N)CnH2n(NH2) (abbreviated as DA; n = 0, 2, 3, or 6) prepared using a low-temperature ammonothermal method to investigate the effect of interlayer spacing on the superconductivity of electron-doped FeSes. The embedded DA formed a monolayer or bilayer in the interlayer of FeSe. The interlayer spacing between nearest FeSe layers could be tuned from 0.87 to 1.14 nm without significant change in the Na/Sr content or the ratio of Fe to Se. Importantly, bilayer phases Na/ethylenediamine- and Sr/hydrazine-FeSe show improved structural stability compared to that of Na/NH3-FeSe. The series of Na- and Sr-intercalated FeSe samples exhibited nearly the same high Tc values of 41-46 and 34-38 K, respectively, irrespective of rather different interlayer spacing d. The peculiar insensitivity for both series can be ascribed to the negligible dispersions of bands along the c axis; i.e., Fermi surfaces are nearly two-dimensional when d is larger than a certain threshold value (dsat) of ~0.9 nm. The Fermi surface shape is already optimal for Tc, and a larger d will not enhance Tc further. On the other hand, the difference in Tc between two series may be explained by the higher carrier doping level in Na/DA-FeSes compared to that in Sr/DA-FeSes, resulting in the increased density of states at the Fermi level and superconducting pairing strength. [ABSTRACT FROM AUTHOR]

Background: Suicide attempts (SA) after psychiatric hospitalization continue to be a major cause of morbidity. Implicit measures may enhance our ability to assess suicide risk. In this context, we describe the first use of the Suicide Opinion Questionnaire (SOQ) to identify post-discharge suicide attempters. Methods: Adult psychiatric inpatients admitted for suicidality (N = 91) were administered a battery of measures including the SOQ, and forty were reached and reassessed for SA at two months post-discharge. Exploratory factor analysis (EFA) on items associated with suicidality was performed to identify latent constructs. Linear discriminant analysis (LDA) was used to optimize factor combination for suicide identification. Results were compared with explicit measures of suicidality, and logistic regression was used to control for other risk factors. Finally, a simplified 9-item scale was derived from the results and its performance compared to that of the linear discriminant function. Results: Twenty items differed between patients with and without SA at intake or follow-up. EFA on these identified two factors: suicide attempters indicated greater acceptability and less moral condemnation of suicide. The LDA-derived discriminant function and 9-item scale was significantly sensitive and specific for post-discharge SA. Conclusions: Attitudes of acceptability and lack of condemnation toward suicide may constitute an implicit measure of suicidality that could contribute to risk assessment in a high-risk population. [ABSTRACT FROM AUTHOR]

Inorganic imides are useful for hydrogen storage and base-catalyzed reactions but are extremely unstable under ambient conditions, which hinders their practical use as functional materials. Here, we demonstrate that NH2 - and H- , as well as NH2-, can be incorporated into the nanocages of the mayenite crystals, [Ca24A128O64]4+(e-)4 and [Ca24A128064]4+( 02-)2, by ammonothermal treatment. We evaluated the reaction conditions and found that the anion exchange reaction proceeded at higher than 500 °C. Raman spectroscopy showed that the N—H band position of encaged NH2- was close to that of CaNH and MgNH crystals. We also studied the reaction pathways that yield NH2 - and NH2- anions and their dynamic motions by 1H NMR spectroscopy. Successive reactions of encaged e- and O2- ions with NH3 yielded NH2 - , NH2-, and H- or OH- , in which the O2- ion reacted more efficiently with NH3. The maximum NH2- concentration and content were ~2.7 X 1020 cm-3 and ~0.25 (wt %)NH, respectively. The short spin—lattice relaxation time found in 1H NMR suggests that the incorporated NH2 - and NH2- rotate or librate in the cage near room temperature. Stability tests showed that the encaged NH2- ions are chemically stable under ambient conditions and in organic solvents. These results are attributed to the encapsulation of active anions within subnanometer-sized cages composed of Ca—O—Al oxide frameworks. The encaged NH2- desorbed as NH3 at higher than 500 °C under vacuum (Ea = 172 kj mol-1). It is thus expected that C12A7:NH2- will function as a reactive nitrogen source for nitrogen transfer reactions by in situ cage degradation. [ABSTRACT FROM AUTHOR]

The discovery of superconductivity in alkali-ammonia cointercalated FeSe has generated intensive interest because of their highest Tc (∼45 K) among iron-chalcogenide superconductors with bulk form. Here, we report the phase diagrams of two series of Li/Na-ammonia cointercalated FeSe1-zTez. When superconductivity is suppressed by Te doping, the magnetic ordering states are emergent. Moreover, a novel phase Lix(NH3)yFe1-zTe2 with possible antiferromagnetism is discovered. This strongly indicates the intimate relation between superconductivity and magnetism in these materials, like in other iron-based superconductors. On the other hand, comparative structure analysis with FeSe1-δTez suggests that although there is remarkable similarity in phase diagrams for both iron-chalcogenide and iron-pnictide superconductors, the different types of anions with different charges lead to the dissimilar controlling factors in superconductivity for both classes of materials. This opens up an opportunity to tune the superconductivity in iron-chalcogenide superconductors in more ways than just one. [ABSTRACT FROM AUTHOR]