Crystals — Open Access Journal of Crystallography

Colonization of Campylobacter concisus in the gastrointestinal tract can lead to the development of inflammatory bowel disease (IBD). Plasmid-encoded C. concisus-secreted protein 1 (Csep1^p) was recently identified as a putative pathogenicity marker associated with active Crohn’s disease, a clinical form of IBD. Csep1^p shows no significant full-length sequence similarity to proteins of known structure, and its role in pathogenesis is not yet known. This study reports a method for extraction of recombinantly expressed Csep1^p from Escherichia coli inclusion bodies, refolding, and purification to produce crystallizable protein. Purified recombinant Csep1^p behaved as a monomer in solution. Crystals of Csep1^p were grown by the hanging drop vapour diffusion method, using polyethylene glycol (PEG) 4000 as the precipitating agent. A complete data set has been collected to 1.4 Å resolution, using cryocooling conditions and synchrotron radiation. The crystals belong to space group P6₂ or P6₄, with unit cell parameters a = b = 85.8, c = 55.2 Å, α = β = 90, and γ = 120°. The asymmetric unit appears to contain one subunit, corresponding to a packing density of 2.47 ų Da⁻¹. Full article

Noncovalent interactions in the single crystal of 3,6-Cl₂-closo-1,2-P₂B₁₀H₈ and in the crystal of closo-1,7-P₂B₁₀Cl₁₀•toluene were analyzed by means of quantum chemical computations. The crystal packing in the second crystal was dominated by numerous B-Cl···Cl-B dihalogen and strong B-P···π pnictogen bonds, the latter of which were characterized by a small length of 3.08 Å and a large interaction energy value, exceeding −10 kcal mol⁻¹. Full article

We report the synthesis and characterization of the first example of an organic dye, PP1, for p-type dye-sensitized solar cells (DSCs) bearing a phosphonic acid anchoring group. PP1 is structurally related to the benchmarking dye, P1, which possesses a carboxylic acid anchor. The solution absorption spectra of PP1 and P1 are similar (PP1 has λ_max = 478 nm and ε_max = 62,800 dm³ mol⁻¹ cm⁻¹), as are the solid-state absorption spectra of the dyes adsorbed on FTO/NiO electrodes. p-Type DSCs with NiO as semiconductor and sensitized with P1 or PP1 perform comparably. For PP1, short-circuit current densities (J_SC) and open-circuit voltages (V_OC) for five DSCs lie between 1.11 and 1.45 mA cm⁻², and 119 and 143 mV, respectively, compared to ranges of 1.55–1.80 mA cm⁻² and 117–130 mV for P1. Photoconversion efficiencies with PP1 are in the range 0.054–0.069%, compared to 0.065–0.079% for P1. Electrochemical impedance spectroscopy, open-circuit photovoltage decay and intensity-modulated photocurrent spectroscopy have been used to compare DSCs with P1 and PP1 in detail. Full article

The IMAGINE and MaNDi instruments, located at Oak Ridge National Laboratory High Flux Isotope Reactor and Spallation Neutron Source, respectively, are powerful tools for determining the positions of hydrogen atoms in biological macromolecules and their ligands, orienting water molecules, and for differentiating chemical states in macromolecular structures. The possibility to model hydrogen and deuterium atoms in neutron structures arises from the strong interaction of neutrons with the nuclei of these isotopes. Positions can be unambiguously assigned from diffraction studies at the 1.5–2.5 Å resolutions, which are typical for protein crystals. Neutrons have the additional benefit for structural biology of not inducing radiation damage to protein crystals, which can be critical in the study of metalloproteins. Here we review the specifications of the IMAGINE and MaNDi beamlines and illustrate their complementarity. IMAGINE is suitable for crystals with unit cell edges up to 150 Å using a quasi-Laue technique, whereas MaNDi provides neutron crystallography resources for large unit cell samples with unit cell edges up to 300 Å using the time of flight (TOF) Laue technique. The microbial culture and crystal growth facilities which support the IMAGINE and MaNDi user programs are also described. Full article

A multi-step annealing method was successfully applied to inclusions reduction and resistivity improvement of CdMnTe:In (CMT:In) single crystals with high resistivity, including a Cd atmosphere annealing step followed by a Te atmosphere annealing step. After the Cd atmosphere annealing step, the density of Te inclusions was reduced distinctly, and it could be also decreased in the subsequent step of re-annealing under Te atmosphere. Both the resistivity and IR transmittance decreased notably after Cd atmosphere annealing, whereas they increased tremendously after re-annealing under a Te atmosphere. The reduction of full-width at-half-maximum (FWHM) and the increase of the intensity of the X-ray rocking curve indicated an improvement of the crystal quality. Meanwhile, after Cd atmosphere annealing, the increase of the intensity of the (D⁰,X) peak and the disappearance of the (A⁰,X) peak in photoluminescence (PL) measurements suggested further that the crystal quality was improved. The detector performance was enhanced obviously after annealing. The higher the annealing temperature, the better the performance was. The detector fabricated by CMT:In slice (Cd atmosphere annealing at 1073 K for 240 h and Te atmosphere re-annealing at 773 K for 120 h) with 9.43% energy resolution and 1.25 × 10⁻³ cm²/V μτ value had the best detector performance. Full article

We report the results of an analysis of the functional capabilities of the KTP crystal and its isomorphs for nonlinear-optical frequency conversion of all types of interactions in the transparency range of the crystal. The possibility of implementing angle, wavelength (frequency), and temperature-noncritical phase matching is shown. Full article

The potential applications of quasicrystals (QCs) in automotive and aerospace industries requires the investigation of their fracture and failure mechanisms under dynamic loading conditions. In this study, Al–Cr–Fe powders were consolidated into pellets using spark plasma sintering at 800 °C for 30 min. The microhardness and dynamic failure properties of the samples were determined using nanoindentation and split-Hopkinson pressure bar technique, respectively. Scanning electron microscopy and transmission electron microscopy were employed to analyze fracture particles. The dynamic failure strength obtained from the tests is 653 ± 40 MPa. The dynamic failure process is dominated by transgranular fracture mechanisms. The difficulty in the metadislocation motion in the dynamic loading leads to the high brittleness of the spark plasma sintered (SPSed) Al–Cr–Fe materials. Full article

The present study envisages the preparation of chromium substituted Nickel ferrite NiCr_xFe_2−xO₄ (x = 0~1.0) powders by a sol-gel auto-combustion method. X-ray diffraction analysis (XRD) showed that the specimens with x > 0.2 exhibited a single-phase spinel structure, and that more content of Cr within a specimen is favorable for the synthesis of pure Ni-Cr ferrites. The lattice parameter decreased with an increase in the Cr concentration. The sample without calcining exhibited a good crystallinity. Scanning Electron Microscopy (SEM) showed the formation of ferrite powders nano-particles, and that the substitution of Cr weakened the agglomeration between the particles. Mössbauer spectra of NiCr_xFe_2−xO₄ showed two normal Zeeman-split sextets that displayed a ferrimagnetic behavior. Furthermore, the spectra indicated that iron was in the Fe³⁺ state, and the magnetic hyperfine field at the tetrahedral tended to decrease with an increase in the Cr substitution. The saturation magnetization decreased by the Cr³⁺ ions, and reached a minimum value (Ms = 4.46 emu/g). With an increase in the annealing temperature, the coercivity increased initially, which later decreased. Full article

The membranes of a pillared-layer structure Metal-Organic Framework (MOF), [Ni(HBTC)(4,4′-bipy)] (HBTC = 1,3,5-Benzenetricarboxylic acid, 4,4′-bipy = 4,4′-bipyridine), have been in situ fabricated on Nickel foam substrate. The orientations of MOF crystals in the membranes can be controlled by the molar ratio of ligand H₃BTC to 4,4′-bipyridine. Scanning electron microscope images and powder X-ray diffraction patterns were used to characterize the membranes and confirm the orientations of their MOF layers. Control experiments have revealed that the presence of homologous metal element Nickel in both the MOF and the substrate and the presence of the neutral 4,4′-bipyridine in the reaction system are necessary for in situ growth of the well-intergrown MOF membranes. This work provides a successful example of directly growing continuous MOF layers on porous metallic substrate with desired orientations by a facile approach. Full article

Hybrid ion-pair crystals involving hexadentate [Fe(III)(3-OMesal₂-trien)]⁺ spin-crossover (SCO) cationic complexes and anionic gold complexes [Au(dmit)₂]⁻ (1) (dmit = 4,5-dithiolato-1,3-dithiole-2-thione) and [Au(dddt)₂]⁻ (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate) were synthesized and studied by single-crystal X-ray diffraction, P-XRD, and SQUID magnetometry. Our study shows that both complexes have similar 1:1 stoichiometry but different symmetry and crystal packing. Complex 1 has a rigid structure in which the SCO cations are engaged in strong π-interplay with molecular surrounding and does not show SCO transition while 2 demonstrates a reversible transition at T_sco = 118 K in a much “softer”, hydrogen-bonded structure. A new structural indicator of spin state in [Fe(sal₂-trien)]⁺ complexes based on conformational analysis has been proposed. Aging and thermocycling ruined the SCO transition increasing the residual HS fraction from 14 to 41%. Magnetic response of 1 is explained by the AFM coupled dimers S = 5/2 with J₁ = −0.18 cm⁻¹. Residual high-spin fraction of 2, apart from a contribution of the weak dimers with J₁₂ = J₃₄ = −0.29 cm⁻¹, is characterized by a stronger interdimer coupling of J₂₃ = −1.69 cm⁻¹, which is discussed in terms of possible involvement of neutral radicals [Au(dddt)₂]. Full article

A new nonlinear optical crystals fluoride carbonate, Na₄Yb(CO₃)₃F, has been synthesized by mild hydrothermal method. The Na₄Yb(CO₃)₃F crystallizes in the noncentrosymmetric space group Cc (no. 9) with the lattice parameters a = 8.018(3), b = 15.929(5), c = 13.950(5) Å and β = 101.425(6)°. The compound Na₄Yb(CO₃)₃F has a high density of [CO₃] groups. The structure can be described as one-dimensional [Na₅Yb(CO₃)₂F₂] chains connected by [CO₃] groups, forming an intricate three-dimensional (3D) framework. Other Na⁺ and Yb³⁺ cations are located in the cavities of 3D network. The powder second harmonic generation (SHG) measurement shows that Na₄Yb(CO₃)₃F features a large SHG response, about 4.3 times that of KH₂PO₄ (KDP), and is a phase-matchable material. In addition, its UV-Vis-NIR diffuse reflectance spectral data indicate that Na₄Yb(CO₃)₃F has a large optical gap about 4.72 eV, which corresponds to the UV cut-off edge of 263 nm. Full article

The growth of MnSn₂ phase during the solidification process of Sn-Mn alloy was crystallographically investigated. The results show that the non-faced spherical caps of the MnSn₂ crystals follow the continuous growth mechanism to grow rapidly along the <001> direction, while the side surfaces the two-dimensional nucleation mechanism to form the low index {100} and {110} facets. An interface structure analysis indicates that the atom planes within the {100} interplanar spacing period (IPSP) has a lower average reticular density than those within the {011} IPSP. This leads to the faster growth rates and thus the shortening and disappearance of the {100} side facets. As a consequence, the partially faceted (i.e., non-faceted spherical caps and faceted side surfaces) MnSn₂ crystals follow an octagonal-base/spherical-cap geometric model (few crystals possess square bases) in three dimensions. Full article

Microwave energy has been in use for many applications for more than 50 years, from communication, food processing, and wood drying to chemical reactions and medical therapy. The areas, where microwave technology is applied, include drying, calcination, decomposition, powder synthesis, sintering, and chemical process control. Before the year 2000, microwaves were used to produce ceramics, semiconductors, polymers, and inorganic materials; in next years, some new attempts were made as well. Nowadays, it has been found that microwave sintering can also be applied to sintered powder and ceramics and is more effective than conventional sintering. Particularly interesting is its use for the synthesis of nanomaterials. This review identifies the main sources of microwave generation, the delivery mechanisms of microwave energy, and the typical designs and configurations of microwave devices, as well as the measurement and construction material problems related to microwave technology. We focus our attention on the configurations, materials, optimized geometries, and solvents used for microwave devices, providing examples of products, especially nanoparticles and other nanomaterials. The identified microwave devices are divided into four groups, depending on the scale, the maximum pressure developed, the highest temperature for sintering, or other special multi-functions. The challenges of using microwave energy for the synthesis of nanopowders have been identified as well. The desirable characteristics of microwave reactors in the synthesis of nanostructures, as well as their superiority over conventional synthetic methods, have been presented. We have also provided a review of the commercial and self-designed microwave reactors, digestors, and sintering furnaces for technology for synthesis of nanomaterials and other industries. Full article

Two polymorphs of the drug compound metergoline (C₂₅H₂₉N₃O₂) were investigated in detail by solid-state NMR measurements. The results have been analysed by an advanced procedure, which uses experimental input together with the results of quantum chemical calculations that were performed for molecular crystals. In this way, it was possible to assign the total of 40 ¹H–¹³C correlation pairs in a highly complex system, namely, in the dynamically disordered polymorph with two independent molecules in the unit cell of a large volume of 4234 ų. For the simpler polymorph, which exhibits only small-amplitude motions and has just one molecule in the unit cell with a volume of 529.0 ų, the values of the principal elements of the ¹³C chemical shift tensors were measured. Additionally, for this polymorph, a set of crystal structure predictions were generated, and the {¹³C, ¹H} isotropic and ¹³C anisotropic chemical shielding data were computed while using the gauge-including projector augmented-wave approach combined with the “revised Perdew-Burke-Ernzerhof“ exchange-correlation functional (GIPAW-RPBE). The experimental and theoretical results were combined in an application of the newly developed strategy to polymorph discrimination. This research thus opens up new routes towards more accurate characterization of the polymorphism of drug formulations. Full article

Magnetic films with a heavy metal layer show strong interfacial interaction of spin-orbit. Spin-orbit interaction is one of the key technologies for spintronics. In this paper, we measured magneto-optical Kerr spectra of Pt/TbCo hetero-structure films on a thermally oxidized silicon substrate (0.3 mm); A: Pt (3 nm)/TbCo (6 nm)/Pt (3 nm), B: Si₃N₄ (10 nm)/TbCo (6 nm)/Pt (3 nm), and C: Pt (3 nm)/TbCo (6 nm)/Si₃N₄ (10 nm). Magneto-optical Kerr spectra of each sample were measured with a wavelength range of 300–700 nm, and were compared to the simulated spectra using the effective refractive index method. In the sample A, which has a symmetric structure, the simulated spectra are consistent with the measured ones. On the other hand, in the samples B and C, with an asymmetric structure, there are some differences between the simulated spectra and the measured ones in a lower photon energy region. This may be caused by interfacial effects of the spin-orbit interaction. Full article

This work explores the effect of lattice solvent on the observed solid-state spin-transition of a previously reported dinuclear Fe(II) triple helicate series 1–3 of the general form [Fe^II₂L₃](BF₄)₄(CH₃CN)_n, where L is the Schiff base condensation product of imidazole-4-carbaldehyde with 4,4-diaminodiphenylmethane (L¹), 4,4′-diaminodiphenyl sulfide (L²) and 4,4′-diaminodiphenyl ether (L³) respectively, and 1 is the complex when L = L¹, 2 when L = L² and 3 when L = L³ (Craze, A.R.; Sciortino, N.F.; Bhadbhade, M.M.; Kepert, C.J.; Marjo, C.E.; Li, F. Investigation of the Spin Crossover Properties of Three Dinuclear Fe(II) Triple Helicates by Variation of the Steric Nature of the Ligand Type. Inorganics.2017, 5 (4), 62). Desolvation of 1 and 2 during measurement resulted not only in a decrease in T_1/2 and completeness of spin-crossover (SCO) but also a change in the number of steps in the spin-profile. Compounds 1 and 2 were observed to change from a two-step 70% complete transition when fully solvated, to a single-step half complete transition upon desolvation. The average T_1/2 value of the two-steps in the solvated materials was equivalent to the single T_1/2 of the desolvated sample. Upon solvent loss, the magnetic profile of 3 experienced a transformation from a gradual SCO or weak antiferromagnetic interaction to a single half-complete spin-transition. Variable temperature single-crystal structures are presented and the effects of solvent molecules are also explored crystallographically and via a Hirshfeld surface analysis. The spin-transition profiles of 1–3 may provide further insight into previous discrepancies in dinuclear triple helicate SCO research reported by the laboratories of Hannon and Gütlich on analogous systems (Tuna, F.; Lees, M. R.; Clarkson, G. J.; Hannon, M. J. Readily Prepared Metallo-Supramolecular Triple Helicates Designed to Exhibit Spin-Crossover Behaviour. Chem. Eur. J.2004, 10, 5737–5750 and Garcia, Y.; Grunert, C. M.; Reiman, S.; van Campenhoudt, O.; Gütlich, P. The Two-Step Spin Conversion in a Supramolecular Triple Helicate Dinuclear Iron(II) Complex Studied by Mössbauer Spectroscopy. Eur. J. Inorg. Chem.2006, 3333–3339). Full article

Graphene is a kind of typical two-dimensional material consisting of pure carbon element. The unique material shows many interesting properties which are dependent on crystallographic orientations. Therefore, it is critical to determine their crystallographic orientations when their orientation-dependent properties are investigated. Raman spectroscopy has been developed recently to determine crystallographic orientations of two-dimensional materials and has become one of the most powerful tools to characterize graphene nondestructively. This paper summarizes basic aspects of Raman spectroscopy in crystallographic orientation of graphene nanosheets, determination principles, the determination methods, and the latest achievements in the related studies. Full article

A single crystal X-ray diffraction study of the new compound [Rb([2.2.2]crypt)]₂[Rb([18]crown−6)][HGe₉]·4NH₃ revealed the presence of the first protonated nine-atom germanide cluster [HGe₉]³⁻. It forms from Rb₄Ge₉ in liquid ammonia, so that [Ge₉]⁴⁻ can be considered as the base and [HGe₉]³⁻ its formally conjugated acid. The H atom is attached to a germanium vertex atom of the basal square plane, as it is known for [RGe₉]³⁻ (R = C₅H₉, Mes, etc.) or [HE₉]³⁻ (E = Si, Sn). In addition, the proton could be located unambiguously in the Fourier difference map. [HGe₉]³⁻ also represents a nido cluster species with 22 cluster-bonding electrons, which can be considered the most stable structure for nine-atom cluster species for all group 14 elements. Full article

Zeolitic imidazolate framework (ZIF-8) membranes have attracted tremendous interest for their high-resolution kinetic separation of propylene/propane mixtures. Current polycrystalline ZIF-8 membranes are supported mostly on planar ceramic substrates (e.g., alumina disks) because of their high thermal, chemical, and mechanical stabilities and facile manufacturing in the labs. Planar supports are, however, not scalable for practical separation applications owing to their low packing density (typically 30–500 m²/m³). On the other hand, ceramic tubes provide order-of-magnitude higher packing densities than planar supports (i.e., much higher membrane areas per module). Here, we report polycrystalline ZIF-8 membranes with thicknesses of ~1.2 μm grown on the bore side of commercially-available ceramic tubes using the microwave seeding and secondary growth technique. The tubular ZIF-8 membranes showed excellent propylene/propane separation factors of ~80, exceeding all currently-reported ZIF-8 membranes on ceramic tubes. It was found that the secondary growth time was critical to enhance the propylene/propane separation factor of the membranes. Membranes were also grown on the shell side of tubular supports, showing the versatility of our technique. Full article