Search

Four novel coordination polymers, {Na2[Co3(H2TTHA)2(H2O)12](H2O)2}·4(H2O) (1), {Na[Cu4(H2TTHA)(HTTHA)(H2O)8](H2O)3}·5(H2O) (2), [Cd3(TTHA)(H2O)4] (3) and [Ca5(HTTHA)2(H2O)8] (4), (H6TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) have been synthesized by self-assembly of the flexible hexapodal acid H6TTHA and corresponding metal salts. The four complexes exhibit novel frameworks with different topologies due to diverse coordination modes and different conformations of the flexible H6TTHA. Complex 1shows a 3D network with (4,4,6)-connected topology constructed from parallel one-dimensional hybrid ribbons with nearly planar 24-membered rings, in which all Co(ii) atoms are located in one plane. Complex 2features a 3D (3,4,4,4,7)-connected network bridged by sodium ions from 2D layer structures which are formed through the interconnection of the tetranucleate units and the flexible ligands. Complex 3possesses hybrid layers constructed from zigzag Cd–O chains. These layers are further linked by the TTHA6−ligands with two configurations, leading to another 3D (3,3,8)-connected framework. The metal ions in complex 4are connected into wall-like infinite metal chains which are bridged by the carboxylate groups of ligands into a 3D (3,3)-connected hybrid framework. The framework is further furnished with the ligands forming hydrophobic channels with approximate sizes 3.5 Å × 9 Å based on the distances of the opposite atoms. The enantiometric pairs of ligands are formed in spite of no asymmetric carbon atom in complexes 1–3. Variable temperature magnetic studies down to 2 K reveal antiferromagnetic interactions in complexes 1and 2. Complexes 3and 4are both highly emissive at room temperature. And the luminescent intensities are largely enhanced once they are frozen to 10 K. [ABSTRACT FROM AUTHOR]

The high pressure structure of α-oxalic acid di-hydrate shows a prototypical behaviour of acid to base proton transfer reaction. The solid state transformation has been characterized by neutron and X-ray diffraction as well as by quantum chemical calculations with periodic boundary conditions. The two resonant configurations playing the most important role in the hydrogen bond mechanism, i.e.a neutral and a charge transfer configuration, are interchanged by modifying the pressure on the system. A different behaviour is predicted for the less common β form, despite an apparently similar packing motif. Implications for the characterization of hydrogen bonds in the solid state are discussed as well as the possibility of estimating internal energy variations from experimental measurements. [ABSTRACT FROM AUTHOR]

The high pressure structure of α-oxalic acid di-hydrate shows a prototypical behaviour of acid to base proton transfer reaction. The solid state transformation has been characterized by neutron and X-ray diffraction as well as by quantum chemical calculations with periodic boundary conditions. The two resonant configurations playing the most important role in the hydrogen bond mechanism, i.e.a neutral and a charge transfer configuration, are interchanged by modifying the pressure on the system. A different behaviour is predicted for the less common β form, despite an apparently similar packing motif. Implications for the characterization of hydrogen bonds in the solid state are discussed as well as the possibility of estimating internal energy variations from experimental measurements. [ABSTRACT FROM AUTHOR]

A series of flexible metal–organic frameworks (MOFs) have been successfully synthesized under hydrothermal condition using 1,3-adamantanediacetic acid (C14H20O4, H2ADA) as a flexible dicarboxylate building block, 4,4′-bipyridine and transition metal ions [Cd(ii), Zn(ii), and Mn(ii)] as metal centers in DMF and aqueous media. These MOFs formulated as [Cd(ADA)(4,4′-bipy)0.5]·(DMF) (Cd-ADA-1), [Mn(ADA)(4,4′-bipy)0.5]·(DMF) (Mn-ADA-1), Zn(ADA)(4,4′-bipy)0.5(Zn-ADA-1), and [Mn(HADA)2(4,4′-bipy)(H2O)2] (Mn-ADA-2) (ADA = 1,3-adamantanediacetate, 4,4′-bipy = 4,4′-bipyridine and DMF = N,N′-dimethyl formamide) display interesting 1D, 2D and 3D structural features depending on the solvent of synthesis. All these MOFs were structurally determined by single-crystal X-ray diffraction. The coordination modes of this ligand are discussed and in addition, thermal stability and hydrogen (H2) and carbon-dioxide (CO2) adsorption properties of Cd-ADA-1, Mn-ADA-1and Zn-ADA-1are also presented. Hydrogen sorption at 77 K and up to 1 atm is found to be 0.42, 0.72 and 1.36 wt% without saturation for Zn-ADA-1, Mn-ADA-1and Cd-ADA-1samples. [ABSTRACT FROM AUTHOR]

In general, β-Ga2O3 films with (2¯01) out-of-orientation have been widely obtained and reported on (0001) sapphire substrates by various growth methods. In this paper, the unusual (3¯10)-oriented β-Ga2O3 films have been epitaxially grown on (0001) sapphire substrates with high crystal-quality under Ga-rich conditions by halide vapor phase epitaxy (HVPE). The out-of-plane epitaxial relationship as (3¯10) β-Ga2O3//(0001) α-Al2O3 has been confirmed by XRD and HRTEM analysis. Under most growth conditions, β-Ga2O3 films exhibit the coexistence of (3¯10) and (2¯01) out-of-plane orientation domains, and increasing the growth temperatures and HCl flow-rates can enhance the growth of (3¯10)-oriented β-Ga2O3. Off-angled (0001) sapphire substrates with off-angles (Δa) toward 〈112¯0〉 have been introduced to control the in-plane domains. It was indicated that the (2¯01)-oriented domains have been gradually eliminated with increasing the off-angles, and pure (3¯10)-oriented β-Ga2O3 films with the best crystal quality reported so far have been obtained while the off-angle was ∼7°. The decrease of the domain boundaries and defects caused by the in-plane rotational domains have led to the improvement of the crystal quality of the as-grown films. [ABSTRACT FROM AUTHOR]

The high temperature stability of zirconia crystals is improved by regulating the content of the stabilizer Y2O3. Cubic zirconia crystals with thermal stability are one of the most active academic research areas for zirconia crystal materials. Nonetheless, the reason for the discoloration of blue cubic zirconia at high temperatures was not determined. In this paper, the spectra of yttria-stabilized zirconia (YSZ) were investigated, and the local structure regulation was carried out to determine the reasons for the colour instability of crystals at high temperatures. Two kinds of blue cubic zirconia samples with different ZrO2–Y2O3 ratios were heated at 800 °C for 1 hour in an air atmosphere. The structure, optical characteristics, and electron binding energy of cubic zirconia crystals with different ratios before and after heating were compared. Sample A changed colour, while sample B remained unchanged. The amount of Y2O3 stabilizers in sample A is three times higher than that in sample B. The significant shift in the absorption cut-off edge of sample A after heating indicates a reduction in the crystal bandgap. The high temperature discoloration of the crystals is attributed to an increase in oxygen vacancies. The study of XPS, XRD, and Raman showed an increase in the concentration of oxygen vacancies in sample A after heating. The thermoluminescence spectra indicate the depth of oxygen vacancy defects and the increase in defect concentration after heating. [ABSTRACT FROM AUTHOR]

The fact that the polymorphic outcome of crystallization is the result of the interplay between the relative thermodynamic stability and nucleation kinetics is well known. This paper presents the synthesis of 2,5-bis(3-bromophenyl)furan (MBPF), for which three polymorphic structures were obtained. The studies included: investigations of three polymorphic structures of this compound using single crystal X-ray diffraction, UV–Vis spectroscopy, circular dichroism spectroscopy, and theoretical approaches. The most important experimental result is the solvent effect on the MBPF conformation stability and in consequence on the crystal growth of the metastable phase. [ABSTRACT FROM AUTHOR]

This paper presents a novel methodology for obtaining the free energy profiles and the self-diffusivity of gases in crystalline microporous materials. The proposed approach is based on X-ray diffraction performed in situ on powder rather than single crystal samples. As proof of concept, we derive the self-diffusion properties of CO2 and CH4 in a metal–organic framework, CAU-10-H. The free energy profiles and self-diffusivity values acquired experimentally using the proposed methodology match those obtained through molecular simulations. This XRD-based methodology can be used for the design of MOFs for membrane gas separation. [ABSTRACT FROM AUTHOR]

First principles calculations of the α-quartz phase of Si1−xSnxO2 predict great benefits of the substitution of Si by Sn with the d11 piezoelectric constant (5.72 pC N−1) for Si0.8Sn0.2O2, which is predicted to be twice that of quartz (2.85 pC N−1). Furthermore, the value of the d11 piezoelectric constant increases four times in the case of substitution with tin in comparison with that for germanium. The first Sn-substituted α-quartz single crystals have been grown under hydrothermal conditions, but the degree of substitution is still very low (xmax = 0.001). The analyses of additional compounds recovered after growth runs indicate that Sn crystallizes in a six-fold coordination with silicon by forming a mixed Si/Sn oxide in the autoclave, which may explain the low degree of substitution in the α-quartz single crystals. A new compound with the formula Na2Si4SnO9(OH)4 is identified, and the structure is determined. This paper predicts high performance of the Sn-substituted single quartz crystals. Crystal growth experiments show that Sn substitution is possible in the structure of quartz-type by using a crystal growth process favoring the formation of four-fold coordinated Sn species [SnO4] in the solution for obtaining a high Sn ratio in the quartz-crystals. [ABSTRACT FROM AUTHOR]

In this paper, the dealloying of ternary Mg66Cu25.5Sn8.5, Mg67Cu18Sn15 and Mg66Cu10.2Sn23.8 alloys was investigated using 1 wt% tartaric acid (TA) and 5 wt% hydrochloric acid (HCl). The formation of nanoporous Cu–Sn alloys or composites was probed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nanobeam-energy dispersive spectroscopy (NB-EDS). The results showed that the structure and phase compositions of the as-dealloyed products depended on the compositions of the precursors and dealloying electrolytes. Ultrafine nanoporous Cu3Sn and Cu6Sn5 alloys could be obtained from dealloying of Mg66Cu25.5Sn8.5 and Mg67Cu18Sn15 precursors in 1 wt% TA, respectively. The dealloying of the Mg66Cu10.2Sn23.8 alloy in 1 wt% TA induced the formation of nanoporous Cu6Sn5/Sn composites. However, using 5 wt% HCl as the dealloying electrolyte led to the partial dissolution of Sn, resulting in the formation of nanoporous Cu41Sn11 and Cu6Sn5 from Mg66Cu25.5Sn8.5 and Mg66Cu10.2Sn23.8 alloys, respectively. The ligaments of the nanoporous structure after dealloying in 5 wt% HCl were also coarser due to the fast diffusion of Cu and Sn with the existence of Cl−. The dealloying mechanisms of the Mg–Cu–Sn alloys were discussed based on the experimental results. The present study provides a facile dealloying approach to fabricate nanoporous Cu–Sn intermetallic alloys via the design of precursors and the selection of dealloying electrolytes. [ABSTRACT FROM AUTHOR]

Well-dispersed uniform spheres (∼0.7–1.5 μm in diameter) of YPO4 and (Y,Ln)PO4 (Ln = Eu, Tb, Dy, Ho, Tm, Ce, and Eu/Tb) tetragonal phosphate hydrates have been directly synthesized via microwave-assisted processing. The polycrystalline spheres, which are made of confined 10–17 nm nanocrystals, are direct solid solutions rather than a mechanical mixture of individual particles. Their growth follows an aggregation process, maintaining the composition of the material. The phosphate hydrates converted into anhydrous tetragonal materials via calcination, and the spherical shape and excellent dispersion of the original particles were well retained up to 1000 °C. Upon UV excitation, the YPO4:Ln3+ samples exhibit characteristic emissions of Ln3+ (Ln = Eu, Tb, Dy, Ho, Tm, and Ce) and yield red, green, near white, green, blue, and blue-green emissions, respectively. The color-tunable emissions (from green to red) can be varied by increasing the Eu content, and the Tb3+→ Eu3+ energy transfer process was observed for the tetragonal phosphate in the Y/Tb/Eu system. The efficiency of the Tb3+→ Eu3+ energy transfer was discovered to be ∼28% for (Y0.88Tb0.02Eu0.10)PO4. The thermal stability of (Y0.88Tb0.02Eu0.10)PO4 is lower than that of (Y0.98Tb0.02)PO4 and (Y0.95Eu0.95)PO4. Thus, the 5D4→7F5 transition of Tb3+ at 546 nm splits into UGRAPHIC DISPLAY="INLINE" ID="UGT1" SRC="UGT1"/→7F5 (at ∼538–546 nm) and UGRAPHIC DISPLAY="INLINE" ID="UGT2" SRC="UGT2"/→7F5 (at ∼557 nm) transitions during the heating process. This phenomenon has been ascribed to the variation of the Tb3+ crystal environment. The UGRAPHIC DISPLAY="INLINE" ID="UGT3" SRC="UGT3"/ energy level gradually shifts to a higher one at an elevated temperature, inducing more and more excited electrons transferring from the higher UGRAPHIC DISPLAY="INLINE" ID="UGT4" SRC="UGT4"/ energy level to the lower UGRAPHIC DISPLAY="INLINE" ID="UGT5" SRC="UGT5"/ one via nonradiative relaxation. Therefore, an enhanced emission intensity at ∼557 nm (UGRAPHIC DISPLAY="INLINE" ID="UGT6" SRC="UGT6"/→7F5 transition) and a weakened one at ∼538–546 nm (UGRAPHIC DISPLAY="INLINE" ID="UGT7" SRC="UGT7"/→7F5 transition) were observed. (Y0.95Eu0.05)PO4/PVA transparent films were successfully fabricated by solution casting, and they exhibit both outstanding flexibility and high transmittances of ≥83% in the 400–850 nm region. The hybrid films can be coated on paper money for anti-fake labeling applications. [ABSTRACT FROM AUTHOR]

The ability to export structures from Mercury to 3D printing file formats allows 3D ellipsoidal models to be printed quickly and easily. Since these physical models are similar to the ellipsoidal plots found in scientific papers and presentations, this will allow students, instructors and crystallographers ready access to a physical model of X-ray diffraction data normally only found on the computer screen or printed page. [ABSTRACT FROM AUTHOR]

In this paper, porous CoP nanoflakes were successfully synthesized through a two-step route. Porous Co3O4 nanoflakes were firstly prepared by pyrolyzing flake-like precursors. Then, porous CoP nanoflakes were produced through the low temperature phosphidation of porous Co3O4 nanoflakes. The phase and morphology of the as-prepared products were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive spectrometry (EDS). Experiments showed that the as-prepared porous CoP nanoflakes presented outstanding catalytic activity in the reduction of some aromatic nitro compounds such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP) and 4-nitroaniline (4-NA), and organic dyes including Rhodamine B, pyronine B, methylene blue and safranine T, in excess NaBH4 solution, which provided a new catalyst option for the reduction of aromatic nitro compounds and the decoloration of organic dyes at room temperature. Interestingly, the preparation approach of the precursor could affect the morphology and the catalytic performance of the final CoP nanostructures. [ABSTRACT FROM AUTHOR]

In this paper, a facile precursor phosphidation route was designed for morphology controlled synthesis of Ni2P nanostructures, employing NiCl2 and NaH2PO2 as the initial reactants in the presence of polyvinylpyrrolidone (PVP) and hexamethylenetetramine (HMT). Experiments showed that under the same hydrothermal conditions, NiHPO3·H2O nanorods and Ni nanospheres were separately obtained via only changing the original amount of HMT. The as-obtained NiHPO3·H2O nanorods and Ni nanospheres could be used as the precursors in low-temperature phosphidation reactions under a N2 atmosphere. Under the same phosphidation conditions, Ni2P nanorods and nanospheres were formed, respectively. The precursor and the final products were characterized by powder X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical performance and the catalytic properties of the Ni2P nanorods and nanospheres were investigated. It was found that the as-obtained Ni2P nanostructures displayed marked shape-dependent properties: the Ni2P nanorods presented better electrochemical performance, such as higher specific capacitance and more stable cycle features, and stronger catalytic activity for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in an excess NaBH4 solution than the Ni2P nanospheres. [ABSTRACT FROM AUTHOR]

Spinel-like Mn1.5Al1.5O4 is an unstable compound whose decomposition is induced by partial oxidation of Mn2+ ions in the temperature range of 300–800 °C in air. According to XRD, two spinel-like phases, Mn0.4Al2.4O4 and Mn2.8Al0.2O4, are formed during both cooling and heating of Mn1.5Al1.5O4. In this paper, we have studied microstructural changes of Mn1.5Al1.5O4 to understand its decomposition mechanism. During heating, low-temperature oxidation takes place and decomposition proceeds via a nucleation and growth mechanism. As a result slightly Al-doped β-Mn3O4 nanoparticles are formed on the surface of the parent spinel particles. On the contrary, cooling leads to high-temperature oxidation that results preferably in spinodal decomposition and formation of alternating Mn- and Al-rich lamellas of nanosized thickness. The present study provides a fundamental reference for the nanostructure design of a Mn–Al–O system and probably some other ones subjected to oxidative decomposition. [ABSTRACT FROM AUTHOR]

Multi-component crystals – salts, co-crystals, or solvates – are usually designed based on the analysis of the complementarity of functional groups and intermolecular interactions of the components. However, no crystal design can do without a practical method of crystal growth. Not all compounds that should be expected to exist based on the “synthon approach” can be prepared in real experiments. This paper aims to illustrate that, in addition to the synthon approach, it is equally important to take into account phase diagrams when searching for practical methods of crystallising multi-component crystals, either as single crystals or as fine particles. Here, we describe the crystallization of a bis(paracetamol) pyridine solvate from a glass-like metastable phase produced by quench-freezing of a paracetamol–pyridine solution with subsequent low-temperature annealing. These procedures must be carried out strictly within the boundaries of the two-phase region “solid solvate + liquor”, which was found only as a result of modelling the phase diagram. The crystal structure was solved by single-crystal X-ray diffraction and compared with co-crystals of paracetamol found in the Cambridge Structural Database. The structure-forming role of the intermolecular interactions and their characteristics were studied by variable-temperature experiments over the range of 100–275 K. This was compared with the structures of pure paracetamol polymorphs and other solvates and co-crystals at ambient and non-ambient conditions. [ABSTRACT FROM AUTHOR]

The structure of doped ceria plays an important role in its chemical reactivity and catalytic performance. However, for the majority of the dopants studied, whether a monophasic solid solution is formed or not is typically determined only by standard X-ray diffraction (XRD). In-depth structural characterization is lacking. In this paper we have prepared Zn-doped ceria nanocrystals exhibiting twice the oxygen storage capacity (OSC) of pure ceria. X-ray photoelectron spectroscopy (XPS) shows that the material is chemically inhomogeneous with zinc enrichment in the surface layer. X-ray fluorescence (XRF) reveals significant compositional inhomogeneity of the material after annealing in air at 1300 °C for 24 h. The standard structural characterization of this material using room temperature XRD and transmission electron microscopy (TEM) fails to reveal its correct phase composition. Based on clear evidence from in situ high temperature XRD we show that, after calcination at 500 °C, the material is not monophasic: X-ray amorphous ZnO is present within the material. The amorphous ZnO crystallizes at 800 °C and undergoes second-stage incorporation at even higher temperatures. This second-stage incorporation is not complete after annealing and trace amounts of ZnO remain according to synchrotron-based XRD. Our work provides valuable insight into the incorporation mechanism of zinc into the ceria lattice, and in particular, raises some doubts on the phase compositions reported in many previous studies on doped ceria. [ABSTRACT FROM AUTHOR]

The paper reports on the experimental and theoretical investigation of bonding properties of potassium amidoborane, (K[NH2BH3]), which is one of the most promising compounds for hydrogen storage material among metallated derivatives of ammonia borane (NH3BH3). For this purpose, in situ Raman spectroscopy, synchrotron X-ray diffraction measurements and complementary ab initio calculations study have been performed under static pressure conditions in the range from ambient pressure up to 25 GPa. Unusual interplay between strong electrostatic and weak dispersive interactions has been revealed, resulting in experimental observation of pressure induced formation of relatively strong conventional hydrogen bonding between negatively charged molecular ions. This finding provides new insight for tailoring materials with desirable properties for various uses. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of the aging of zeolite A hydrogel under high pressure on the synthesis of zeolite A. The effects of the aging pressure, aging time and type of gas are examined. The products are characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicate that high-pressure aging leads to an increase in the nucleation rate, facilitating the formation of zeolite A with high crystallinity, small particle sizes and narrow particle size distribution. The type of gas also exerts an influence on the synthesis of zeolite A, as hydrogels aged under high pressure in a gas with a higher solubility in water can produce zeolite A with smaller particle sizes. Thus, by adjusting the aging pressure and the type of gas used, the size of the resulting zeolite A can be controlled. The mechanism of the high-pressure aging is related to the interaction of the gel with the dissolved gas. An influence of the aging of hydrogels on the syntheses of zeolite Y, silicalite-1 and SAPO-34 is also observed. [ABSTRACT FROM AUTHOR]

In recent years, BiVO4 has been extensively studied as a promising visible-light-driven catalyst candidate due to its great visible-light absorbing ability. In this paper, novel core-shell structured (CSS) BiVO4 hollow spheres with an ultra-high specific surface area were synthesized via a one-pot, surfactant- and template-free hydrothermal route. The as-obtained products were characterized by scanning electron microscopy, X-ray diffraction, nitrogen adsorption-desorption experimentation, Raman and UV-vis absorption spectroscopy, respectively. The formation mechanism of the BiVO4 products was proposed in terms of the morphological evolution with prolonging the reaction time. The as-prepared CSS BiVO4 hollow spheres similar to Russian dolls were comprised of an inner core and an open outer shell, leading to an ultra-high specific surface area about fifty times that of solid spherical counterparts fabricated by the traditional solid-state reaction method. As a result, the CSS BiVO4 hollow spheres exhibited a superior photocatalytic activity over not only solid BiVO4 spheres but also other morphological products such as biscuits and plates in the photodegradation of rhodamine B under visible-light irradiation. [ABSTRACT FROM AUTHOR]

In this paper, the novel straw sheaf-like CuO single crystals have been, for the first time, prepared through a facile two-step process: hydrothermal and subsequent calcination. We have mainly investigated the influences of the copper(II) concentration, the added amount of hexamethylenetetramine (HMT), reaction temperature and time on the samples. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and nitrogen sorption isotherms. The results show that the formed CuO straw sheaves are fairly uniform, and the single straw grows preferentially along the [001] orientation. It is proposed that the CuO straw sheaves form by a crystal splitting growth process. Furthermore, under visible-light irradiation, the CuO straw sheaves exhibit 5.3 times higher activity than the irregular sample for the degradation of rhodamine B (RhB), which has been ascribed to the exposed {110} facets and high crystallinity. [ABSTRACT FROM AUTHOR]

In this paper, a method to synthesize anatase TiO2 nanorods by hydrolysis of titanium(IV) isopropoxide (TTIP) in the presence of benzyl alcohol and acetic acid at 210 °C was tested. The novelty of the present approach relies on the evaluation of the shape-controlled synthesis of anatase TiO2 nanocrystals via a microwave-solvothermal method in 45 min. The different TiO2 nanocrystals were obtained by tuning the TTIP/acetic acid ratio under optimized synthetic conditions and were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), micro Raman (together with microphotoluminescence) and FT-IR spectroscopies. The acetic acid coordinated on the nanocrystal surface was removed by the reduction of its carboxyl group via a "super-hydride reaction", and the photocatalytic activity of bare TiO2 nanocrystals, under visible light irradiation, was also evaluated: the best performing TiO2 anatase nanocrystals exhibited a discrete photoactivity, completely degrading Rhodamine B solution in five hours. [ABSTRACT FROM AUTHOR]

In this work, we introduce a simple approach to fabricate orthorhombic MoO3 (α-MoO3) nanobelts using sodium molybdate and dodecylbenzenesulfonic acid (DBSA). Importantly, DBSA not only acts as a reagent to provide H+, but also serves as a surfactant to stabilize and manipulate the morphology of the as-obtained products. Themorphology, chemical composition and crystal structure of the as-prepared α-MoO3 nanobelts were systematically characterized by scanning electronmicroscopy, energy dispersive spectroscopy, selected area electron diffraction, X-ray diffraction, transmission electron microscopy (including high-resolution imaging), Fourier transformation infrared spectroscopy and Raman spectroscopy. The results show that the dimensions of the as-prepared α-MoO3 nanobelts are 150-350 nm in width, 50-70 nm in thickness and 1-5 μm in length. Moreover, the electrochemical properties of the samples were analyzed utilizing cyclic voltammetry (CV), chronopotentiometry (CP) and AC impedance in a 0.5 M aqueous Li2SO4 solution. These studies reveal that the maximum specific capacitance of the α-MoO3 nanobelts is much higher than those MoO3 nanomaterials in recently reported papers. Furthermore, the charge-discharge stability measurements indicate a retention of specific capacitance of about 95% after 500 continuous charge-discharge cycles at a current density of 0.25 A g-1, demonstrating that the as-prepared α-MoO3 nanobelts can serve as most excellent electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

A methodology to increase the device purpose yield of a KDP crystal is reported in this paper. The method is based on increasing the cross-section of the prismatic sector {100} of the growing KDP crystal at the expense of the unusable pyramidal cap portion by restricting the growth of the crystal up to a particular height, decided by the solution–air interface in the crystallizer. Due to the lack of solution above the interface, the crystal ceases to grow in the upward direction whereas it continues to grow laterally. This leads to an increase in the usable volume of the grown crystal for the fabrication of crystal elements required for electro-optic switching and frequency conversion applications. An empirical relationship has been introduced as a condition to grow flat-top shaped KDP crystals. It relates the growth parameters with the apparatus design parameters. Several flat-top shaped crystals have been grown as a validation of the growth methodology and the empirical relationship. The influence of the growth methodology on the crystalline quality of the grown crystal was assessed by measuring the defect structure of different sectors of the grown crystal by X-ray topography (XRT). The crystalline perfection was estimated by recording the rocking curve widths using high resolution X-ray diffraction (HRXRD). The optical quality was assessed by measuring the UV-vis-NIR transmission of the different sectors of the crystal and the refractive index homogeneity using interferometric techniques of conoscopy. It is found that restricting the growth of the crystal in the [001] direction by the solution–air interface does not have any detrimental effect on the crystalline and optical qualities of the grown crystal. [ABSTRACT FROM AUTHOR]

In this paper, a porous Sialon polytypoid material with multilayered structure was in situ synthesized at 1700 °C for 3 h in a nitrogen atmosphere via a nitriding process. The plate-like Sialon grains were observed using a scanning electron microscope (SEM), and the chemical composition, structure, chemical state and optical absorption of this material were characterized by energy dispersive X-ray spectroscopy (EDX), synchrotron X-ray diffraction (SXRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). There are four layers with two ranges of grain sizes. The grains with sizes of 18–35 μm are in the inner layer (layer-4) and light-grey, while those grains with bigger sizes of 60–80 μm are present in the outer layers in green colour. These two types of grains have a slight difference in chemical composition, i.e. (La,Sm)0.1Si8Al14O5N21.1 and (La,Sm)0.33Si6Al12O1N21, respectively. They are polytypoids with different structures, which precipitated from the lanthanide-rich Sialon glass. The chemical states of the elements were different as indicated from XPS data. It is believed that the colour and size differences within layers resulted from the intrinsic differences of chemical composition, structure and chemical state of the two types of grains. This porous ceramic might be of potential applications in water treatment, building and automotive industries as a functionally gradient material (FGM) or ceramic filter. [ABSTRACT FROM AUTHOR]

A series of one-dimensional (1-D) N-succinopyridine-based complexes: [Cu(L−)(H2O)2]Cl·2H2O (1), [Pr(L−)(H2O)4]Cl2 (2), [Ln(L−)(H2O)5]Cl2·3H2O (Ln = Eu (3), Gd (4)), and [Er(L−)(H2O)4]Cl2·H2O (5) (HL = N-succinopyridine (−OOC–CH(N+C5H5)–CH2–COOH)) have been prepared and characterized by single-crystal X-ray diffraction. The frameworks of complexes 1, 2 and 5 constructed from dinuclear metal building blocks exhibit 1-D double-strand loop-like chains; these chains are further connected to each other by hydrogen bonds forming a 3-D supramolecular architecture. Whereas complexes 3 and 4 feature hydrogen bonding 2-D supramolecular networks assembled from 1-D chains that are constructed from mononuclear metal building blocks. The effects of different metal ions, steric hindrance and coordination diversities of HL on the polymeric architectures have been discussed. In addition, thermogravimetric and magnetic properties of these complexes were also investigated in this paper. [ABSTRACT FROM AUTHOR]

Nd3+ and Mg2+ co-doped LiTaO3 (Nd:MgO:LT) crystal has great potential for applications in self-frequency doubling (SFD) lasers, and self-optical parametric oscillation (SOPO) infrared lasers. However, a related high performance laser device has not yet been realized. No reliable data on the basic physical properties of Nd:MgO:LT have been obtained, because of the lack of high quality Nd:MgO:LT crystals available due to the great difficulty in growing this crystal. In this paper, by optimizing the growth parameters and the thermal field by means of simulation, a high quality Nd3+ and Mg2+ co-doped LiTaO3 crystal was grown by a modified Czochralski method. A comprehensive characterization of the crystal, including structure, composition, thermal properties, and CW laser performance, was performed. The experimental results indicate that Nd:MgO:LT is a monocrystal with strong anisotropic physical properties. The anisotropic thermal expansion was confirmed by observing the lattice parameter variation via temperature-dependent XRD analysis. Some important physical property data, such as thermal diffusivity, thermal conductivity and specific heat of the Nd:MgO:LT single crystal are reported for the first time, and should be of great utility for the application of this crystal. A CW laser output power of 3.58 W with an optical-to-optical conversion efficiency of 11.55, and a slope efficiency of 13.78%, was achieved with an incident pump power of 31 W, which is the highest laser output reported for this kind of crystal. It is demonstrated that single crystal Nd:MgO:LT will have important applications in SFD and SOPO lasers. [ABSTRACT FROM AUTHOR]

In the present study, we combine high-resolution synchrotron powder diffraction with SEM to shed additional light on the arrangement of an intra-crystalline organic matrix in the nacre from red abalone. SEM observation and synchrotron diffraction analysis show that an intra-crystalline organic matrix exists inside nacre tablets and is adsorbed on the (002) atomic plane in an isolated form. Most probably, the intra-crystalline organic matrix is nacrein and its atomic groups are connected with the (012) atomic plane. The findings provide a new understanding of the arrangement of intra-crystalline organic matrices and may facilitate studies on the formation mechanism and the strengthening and toughening mechanism of the nacre. It is worth pointing out that the new experimental method in this present paper can be extended to nanostructural research of other biominerals. [ABSTRACT FROM AUTHOR]

In this paper, a facile and economical route based on an oxidation induced phase transformation in alcoholic solution was developed to prepare mesoporous CeO2nanoflowers. The whole process could be divided into two steps: the formation of Ce(HCOO)3with flower-like structures and the oxidation induced phase transformation from Ce(HCOO)3to CeO2with unchanged morphology in the alcoholic solution. TEM results revealed that the CeO2nanoflowers consist of rods with length and diameter of 100 and 30 nm, respectively. N2adsorption/desorption experiments indicated that the CeO2nanoflowers display mesoporous structures with a mean pore size of 4 nm, and the BET surface area and pore volume of such flower-like structures are 95.7 m2g−1and 0.173 cm3g−1, respectively. Prompted by the mesoporous structure, high surface area and high pore volume, we speculate that these mesoporous CeO2flowers could be promising candidates for practical catalytic application. [ABSTRACT FROM AUTHOR]

In this paper, GaN films were grown on an H3PO4etched MOCVD-GaN/Al2O3template (EMGA) by hydride vapor phase epitaxy (HVPE). The GaN film grown on the EMAG template showed a smaller full width at half maximum (FWHM) of the (002) and (102) reflections in the XRD measurement than that grown on the MOCVD-GaN/Al2O3(MGA) template. A stronger PL band edge emission was observed for the GaN grown on the EMGA template compared to the MGA template. Defect related yellow luminescence was observed for GaN grown on the MGA template, which did not appear for the EMGA template. The Raman results showed that the stress of the GaN grown on the EMGA is much smaller than that on the MGA template. The penetrated etch pits played an important role in the reduction of threading dislocations. These results indicate that the quality of the GaN films is improved by using an EMGA template. [ABSTRACT FROM AUTHOR]

The preparation of large MCM-41 single crystals as well as their controllable morphologies has very important meanings not only for their potential applications but also for the exploration of the new morphogenetic mechanism for some special mesoporous crystals. In this paper, a novel crystal form of hexagonal circular bicone of MCM-41 crystal, which is the combination form of thee hexagonal bipyramid and circular bicone forms, has been observed. The MCM-41 single crystals which originally remained the same can grow larger to nearly ∼10 micron viamultiple-growth in extremely diluted ammonia solution, and were characterized by SEM, POM, TEM, XRD etc.The morphology of the MCM-41 crystal can also be controllably modulated by adding alkali salts to the synthetic system. Increasing the concentration of KCl can cause the aspect ratio and the conical angle to increase consistently and the result displays monotonicity with a certain statistical deviation. A fluctuation effect has an influence on the surface energy and eventually leads to the evolution from a single crystal to one with non-crystalline characteristics. [ABSTRACT FROM AUTHOR]

In this paper, the influence of alloy composition, dealloying solution and elemental doping on the dealloying process of rapidly solidified Mg–Ag based alloys and the formation of nanoporous silver (NPS) has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The results show that NPS and nanoporous silver-palladium (NPS–Pd) alloys can be fabricated by dealloying the Mg–Ag based alloys in acid media under free corrosion conditions. The NPS and NPS–Pd exhibit an open, three-dimensional bicontinuous interpenetrating ligament-channel structure. Furthermore, alloy composition and phase constitution of the Mg–Ag precursors have a significant influence on the ligament/channel size and the formation of cracks in NPS. The length scales of ligaments/channels in NPS can be tuned by simply changing the dealloying solution. Crack-free NPS with good mechanical integrity and small ligament/channel sizes can be obtained by dealloying the Mg–Ag alloys in suitable acid solutions. Moreover, the addition of Pd into Mg–Ag has a significant influence on the dealloying process and results in the formation of ultrafine bimodal NPS–Pd with ligaments/channels of ∼5 nm. The NPS–Pd alloy shows excellent hydrogen sensing properties with stable sensitivity, fast response and low detection limit. Our present findings provide implications for control and functionalization of nanoporous metals or alloys by alloy design, selection of dealloying media and elemental doping. [ABSTRACT FROM AUTHOR]

By adjusting the molar ratio of the reactants H3PO4and Na2MoO4, four new metal–organic frameworks, namely, CoH(bix)4[PMoVI8VV4O40(VIVO)2] (1), (H2bix)2(NaHP2Mo5O23)·2H2O (2), H2(bix)4[Cd(H2O)4][Cd(HPO4)4(H2PO4)4(MoO2)12(OH)6]·10H2O (3) and (H2en)3(Co3P4Mo4O28) (4) (bix = 1,4-bis(imidazol-1-ylmethyl)benzene, en = 1,2-ethylenediamine), have been hydrothermally prepared and characterized by elemental analyses, IR spectroscopy, TG analyses, and single-crystal X-ray diffraction. Compound 1consists of straight chains based on pseudo-Keggin [PMoVI8VV4O40(VIVO)2]3−polyanions and [CoH(bix)4]3+complex fragments, which are further connected into a three-dimensional (3D) open framework by hydrogen bonding interactions between polyanions and organic bix ligands . Compound 2shows 3D supramolecular networks constructed from weak interactions between free biprotonated bix, water and oxygen atoms of polyanions [P2Mo5O23]6−. In compound 3, [Cd(HPO4)4(H2PO4)4(MoO2)12(OH)6]4−polyanions are linked by [Cd(H2O)4]2+cations to build one-dimensional (1D) chains. Then weak interactions between free bix ligands, water and oxygen atoms of the polyanions extend these 1D chains to 3D supramolecular frameworks. Compound 4exhibits open-framework structures. Interestingly, it also shows 1D left and right-handed helical chains and 2D (6,3)-layers. The molar ratio of the reactants H3PO4and Na2MoO4influence the transformation of the phosphomolybdate clusters in compounds 1–4. The electrochemistry and photocatalysis properties of these compounds have also been investigated in this paper. [ABSTRACT FROM AUTHOR]

The availability of high-quality silicon carbide (SiC) single crystals with large diameter is a key issue in the development of the full potential of SiC-based device technology. The formation and suppression of misoriented grains (MGs) in the marginal area of as-grown 6H-SiC single crystals are mainly discussed in this paper. The polytype of the MGs is identified to be mainly 6H-SiC by Raman spectroscopy and XRD. Results of modulation growth, in which different stages are decorated with nitrogen, reveal that the growth rate of MG is higher than that of the matrix. Owing to the MG orientation deviating from [0001], no micropipe has been observed in the etched MG samples. At the same time, there exist many thermal decomposition cavities (TDCs) at the initial growth stage, which indicates that the MG may result from a TDC. Based on this possible formation process, a method viasputtering carbon film on C-terminated (0001) 6H-SiC surface for eliminating TDCs is proposed, which may be helpful to suppress formation of MGs, hence to effectively grow SiC crystals with high quality and large diameter by moderate controls of critical growth conditions in the PVT technique. [ABSTRACT FROM AUTHOR]

In this paper, three dimensional mesoporous CeO2hierarchical structures were synthesized through the thermal decomposition of cerium formate precursors, which were prepared by a solvothermal method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), and Thermal gravimetric (TG) was applied to characterize the precursors. Urchin-like Ce(HCOO)3precursors were prepared using dimethyl sulfoxide (DMSO) and ammonia solution (1 M) as solvent and base source, respectively, while coral-like Ce(HCOO)3precursors were prepared using dimethyl formamide (DMF) and NH4HCO3as solvent and base source, respectively. The formation mechanism of the hierarchical structured precursors was proposed involving a process of anisotropic growth–H2O induced self-assembly–oriented aggregation and disassembly–Ostwald ripening. CeO2hierarchical structures were obtained by annealing the corresponding Ce(HCOO)3precursors at 400 °C for 60 min. N2adsorption–desorption isotherms indicate that both CeO2hierarchical structures derived from their Ce(HCOO)3precursors display large surface areas and high pore volumes. In addition, the as-prepared CeO2catalysts with hierarchical structures are highly active for conversion of CO to CO2. [ABSTRACT FROM AUTHOR]

In this paper, we report a facile electrochemical deposition route for preparation of thicket-like lead telluride (PbTe) microstructures built up of plentiful nanoflakes. PbTe was potentiostatically electrodeposited on Cu substrates from an aqueous system containing Pb(NO3)2and Na2TeO3in the presence of proper amounts of disodium salt of ethylendiaminetetraacetic acid (EDTA·2Na) and tartaric acid. The phase and morphology of the as-prepared product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (HR/TEM), and scanning electron microscopy (SEM). Some factors influencing the formation of thicket-like PbTe microstructures were systematically investigated, including the deposition time and potential, the molar ratio of EDTA/tartaric acid, the original amounts and sources of Pb2+ions. Experiments showed that the molar ratio of EDTA/tartaric acid, the deposition time and potential could markedly affect the morphology of the final product. [ABSTRACT FROM AUTHOR]

In this paper, we report on the shape-controlled synthesis of porous FeVO4nanorods and nanoparticles through a facile route, including hydrothermal synthesis of FeVO4·1.1H2O precursors and sequential post-calcination at 550 °C for 24 h. The porous FeVO4nanorods and nanoparticles were obtained with reactant concentrations of 0.3 and 0.02 mol L−1, respectively. The Rietveld refined XRD, SEM and TEM/HRTEM characterization shows that the porous FeVO4nanorods and nanoparticles have a triclinic crystal structure, while the average diameter of the porous FeVO4nanorods is about 100 nm and the size of the porous nanoparticles is in the range of 80–150 nm. N2adsorption–desorption isotherms show that both the porous FeVO4nanorods and nanoparticles exhibit mesoporous structures with specific surface areas of 6.7 and 9.7 m2g−1, respectively. [ABSTRACT FROM AUTHOR]

In this paper, large dendritic Bi nanostructures were synthesized viaa facile electrochemical deposition route at room temperature, employing Bi(NO3)3·5H2O as the reactant without assistance of any additive and protection of an inert atmosphere. The phase and morphology of the as-prepared product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometer (EDS), (high resolution) transmission electron microscopy (HR/TEM), selected area electron pattern (SAED) and scanning electron microscopy (SEM). Some factors influencing the formation of dendritic Bi nanostructures were investigated, including the depositing time, current, complexing agent, surfactant, the original amount and existing state of Bi(iii). Experiments showed that the existence state of Bi(iii) in the system, the depositing time and some complex agents could markedly affect the morphology of the final product. Also, the as-obtained product is found to have potential applications in the detection of trace metal such as Cd in water resource. [ABSTRACT FROM AUTHOR]

Solvents have a significant effect on crystal morphology, particularly for polar organic crystals. However, the role played by solvents in enhancing or inhibiting crystal growth is still not completely understood. In this paper we investigated the morphologies of dl-alanine as a model of organic polar crystals grown from a mixture of aqueous solutions, with organic solvents such as isopropyl alcohol (IPA) and ethanol. dl-alanine crystals were grown from pure water for a large range of supersaturation in various solutions of water-isopropyl alcohol (IPA) and water–ethanol. The crystal morphology formed under different crystallization conditions was analyzed using an electron microscope and X-ray diffraction to determine the specific effects of each solvent. It was found that the quantity of the solvents in the crystallization solutions has a large influence on the crystal tip morphology, and on the crystal aspect ratio. Molecular dynamic simulations were used to determine the relative growth rates of different crystallographic planes and crystal morphology. A combination of experimental morphology and simulated morphology calculated using a theoretical method allows us to understand the role played by solvents on crystal growth and crystal morphologies of dl-alanine crystals. [ABSTRACT FROM AUTHOR]

In this paper, mesoporous Eu2O3microspheres and Eu2O3nanoparticles-wires were synthesized and characterized by XRD SEM, and TEM. By means of adjusting synthetic parameters, two kinds of Eu2O(CO3)2H2O precursors with sphere-like and wire-like morphology were obtained respectively. By calcinating the precursors at 650 °C, the high-quality mesoporous Eu2O3microspheres and Eu2O3nanoparticle-wires showed strong optical properties. Both fluorescence spectrum and XRD patterns proved that as-synthesized mesoporous Eu2O3microspheres and Eu2O3nanoparticle-wires had cubic phase structures. [ABSTRACT FROM AUTHOR]

Polymorphism in cocrystals is increasingly gaining interest because of the overwhelming interest in pharmaceutical cocrystals. In this paper, we report a 1 : 1 cocrystal of an analgesic drug, ethenzamide (EA), with ethylmalonic acid (EMA) which exists in two polymorphic forms. Both the polymorphs were characterized by various analytical techniques, such as single-crystal and powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), hot-stage microscopy (HSM) and variable temperature X-ray diffraction (VTXRD). Crystal structure analysis suggests that the EMA molecules in both the polymorphs adopt different conformations but feature a common hydrogen bonding motif. Thermal analysis suggests that the polymorphs are related enantiotropically. Based on the information obtained from the thermal data and various other experiments, a semi-schematic energy-temperature diagram was constructed. Interestingly, it was observed that the polymorphic outcome of solid-state grinding is remarkably dependent on the polarity of the solvent used in the solvent-drop grinding experiments. [ABSTRACT FROM AUTHOR]

In this paper, three-dimensional mesoporous Zinc oxide (ZnO) hierarchical structures were fabricated from the thermal-decomposition of layered basic zinc carbonate (LBZC) precursors, which were synthesized by an urea hydrothermal method without a surfactant. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the LBZC precursors and mesoporous ZnO hierarchical structures. The results of N2adsorption–desorption isotherms indicated that the pore size distribution and specific surface area can be tailored by varying the urea amount and the annealing temperature. Photocatalytic activity of the mesoporous ZnO was evaluated using the degradation of methyl orange. The influence of urea content and annealing temperature on the morphology and surface specific areas and the effect of BET areas on the photocatalytic activity were discussed. Hierarchical ZnO flowers with 0.006 mol urea added annealed at 300 °C showed good photocatalytic activity. [ABSTRACT FROM AUTHOR]

In the present paper, we report successful synthesis of FeMoO4hierarchical hollow spheres with 1.0 µm in diameter viaa simple, rapid and reliable microwave-assisted solution-phase approach. The phases and morphologies of the products have been characterized by powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Some factors influencing the morphology of the final product have been investigated. These experiments indicate that the self-assembly of FeMoO4nanoparticles at the water/gas interface is responsible for the formation of a hierarchical hollow structure. [ABSTRACT FROM AUTHOR]

This paper reports two structurally unique CuCN-terpyridine hybrid networks of 4′-p-tolyl-2, 2′ : 6′, 2″-terpyridine (ttpy) prepared under solvothermal condtions: [(CuCN)5(ttpy)]n(1), [(CuCN)3(ttpy)]n(2). Complex 1features a tri-layer structure with 3-connected binodal (8210)·(8210) topology, while complex 2features unusual honeycomb-like layer structures. The adjacent honeycomb-like layers consist of the opposite handed helical CuCN-ttpy chains. In both complexes, each ttpy coordinates two copper(I) atoms with short Cu–Cu distances, and the side pyridyl group rotates in a certain angle from the central pyridyl plane directing the formation of the diversified networks. [ABSTRACT FROM AUTHOR]

In this paper, flowerlike Co11(HPO3)8(OH)6superstructures were selectively synthesized viaa facile hydrothermal route on a large scale in the presence of a certain amount of Ni2+ions, employing CoCl2·6H2O and NaH2PO2·H2O as the reactants, NaHCO3as the pH adjustor. HPO3−ions were provided based on the dismutation of H2PO2−ions in a weak basic solution. The reaction was carried out at 170 °C for 10 h. The as-obtained products were characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), field emission scanning electron microscopy (SEM), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). Research showed that the Ni2+ions in the system played a crucial role in the formation of flowerlike Co11(HPO3)8(OH)6superstructures. Some factors influencing the morphology of Co11(HPO3)8(OH)6, including the reaction time, temperature, and the kinds of metal ions were investigated. A possible growth mechanism was proposed. [ABSTRACT FROM AUTHOR]

The organic semiconductor dibenzotetrathiafulvalene (DB-TTF) presents, at ambient conditions, four polymorphic modifications. In addition to the already known monoclinic structure (α) with Z= 2, we have resolved by single crystal X-ray diffraction (XRD) a second crystal structure (β), also monoclinic but with Z= 4. Two other polymorphic modifications (γ and δ) have been found by means of lattice phonon confocal Raman microscopy and XRD. In this paper we present a series of growth experiments, from vapour or from solution, in films and in the bulk phase, describing the variety of transformations which occur among the different phases and their mixing, also at a micrometric scale. Quasi harmonic lattice dynamics calculations satisfactorily reproduce the structures of the α and the β polymorphs and help the phonon assignment of polarized Raman spectra in single crystals. [ABSTRACT FROM AUTHOR]