Growth Of Crystal Faces Research Articles

Combined study of Au-bearing arsenopyrite of orogenic gold deposits (NE Asia): High resolution 3D X-ray computed tomography, LA-ICP-MS, EMPA data

The distribution of gold in small acicular arsenopyrite of a pyrite-arsenopyrite association from Suzdal (Eastern Kazakhstan), Olympiada (Yenisei Ridge, Russia) and large pseudorhombic arsenopyrite crystals from Bazovskoe (Yakutia, Russia) orogenic-type deposits were investigated. On orogenic gold deposits in NE Asia, occurring mainly in black shales, two productive stages of ore deposition are distinguished, which correspond to two morphological varieties of arsenopyrite. At the early stage, fine-grained acicular-prismatic arsenopyrite with invisible gold was deposited; at the late stage, tabular arsenopyrite in association with free visible gold was formed. The samples of gold-bearing arsenopyrite were analyzed using Scanning Electron Microscopy, Electron Microprobe Analyses, Atomic Absorption and Laser Ablation Inductively Coupled Plasma Mass Spectrometry in combination with High Resolution 3D X-ray Computed Tomography (HRXCT). HRXCT does not destroy the studied mineral during the investigation. That technique permits to do an estimation of the amount of gold inclusions in minerals or host rocks and draw reasonable conclusions about the gold content of the ores, to study in detail the distribution patterns of metal inclusions (associated with certain minerals, cracks, crystal growth faces, etc.) and to determine the form of the gold. It can be used to understanding of the genesis of productive mineral associations, and to developing optimal technological schemes for gold extraction

Synthesis, crystal structure, and physical properties of a triangular-lattice magnet K2Co(HPO4)(C2O4)(OH2)⋅H2O

A previously unreported geometrically frustrating cobalt oxalatophosphate, K2Co(HPO4)(C2O4)(OH2)⋅H2O (KCoCP), is solvothermally synthesized and characterized. KCoCP shows a typical two-dimensional (2D) layered structure of [Co(HPO4)(C2O4)(OH2)]2− separated by K+ and H2O, which is isostructural to the previously reported Fe analogue. Specifically, the magnetic Co2+ ions sit on a distorted triangular lattice (TL) and introduce geometrical frustration into the system. The mainstay of the 2D layer [Co(HPO4)(C2O4)(OH2)]2− is cobalt oxalate skeleton with HPO4 and H2O groups staggering on both sides. The Bravais–Friedel–Donnay–Harker (BFDH) theory, which is used to predict the polyhedral morphology and crystal growth faces, indicates a chamfer polyhedron morphology of KCoCP crystal. UV–vis diffuse reflection and electronic structure calculation suggest KCoCP being a semiconductor with an indirect band gap (0.214 ​eV). The absence of long-range magnetic ordering for KCoCP is proved via a combination of magnetic susceptibility and specific-heat measurements down to 1.8 ​K. Thus, KCoCP shows potential to investigate unconventional low temperature physical properties in TL system.

Minimalist preparation and photocatalysis properties of a spinyball-like indium-based composite suitable for different light conditions

The CdIn2S4/In2S3/CaIn2S4 composites were successfully prepared by an extremely simple programmed temperature hydrothermal method, which present a spinyball-like structure with a micro-sphere diameter of about 2.5–3 µm. X-ray diffraction analysis (XRD) results show that CaIn2S4 and CdIn2S4 exist in the form of cubic phase, and In2S3 exists in the form of cubic β-In2S3 in the composites. By discussing the relationship between the change of strain gravity and the change of cell parameters of CaIn2S4 after compounding In2S3 and CaIn2S4, the effects of crystal lattice change, crystal face growth and inhibition on the photocatalytic activity were studied. Meanwhile, through the photoluminescence spectra (PL), electrochemical impedance spectra (EIS), and transient photocurrent response analysis, the recombination of CaIn2S4, In2S3, and CdIn2S4 can accelerate the charge transfer and inhibit the recombination of electron–hole pairs in the CdIn2S4/In2S3/CaIn2S4 composites, so that higher photocatalytic performance can be obtained. Using methyl orange (MO) as the degradation object, the photo-degradation properties of the as-composites were studied and compared, and the results show that spinyball-like In2S3/CaIn2S4 and CdIn2S4/In2S3/CaIn2S4 exhibit high photocatalytic activity for degradation of MO under visible light and simulated sunlight, respectively. Furthermore, with Pt loaded as a co-catalyst, in Na2S aqueous solution, the hydrogen production rate of CdIn2S4/In2S3/CaIn2S4 photocatalysts is 74.9 μmol·g−1 (8 h), which is 8 times that of the commercially available TiO2. Furthermore, based on the results of the trapping experiment of CdIn2S4/In2S3/CaIn2S4, a possible photocatalytic mechanism was proposed, and the effect of multi-path photo-generated electron migration in the photocatalytic process was explained.

Quantifying the effect of solvent on the morphology of organic crystals using a statistical thermodynamics approach

A method for predicting the effect of solvent on the morphology of organic crystals is presented, providing an efficient screening tool for identifying ideal crystallization solvents. The solvent effect is estimated by the computation of chemical potentials and activity coefficients of crystal surfaces using a first principles-based statistical thermodynamics approach. Density functional theory and COSMO-RS are utilized to determine the activity coefficients of the crystal growth faces of a selection of active pharmaceutical ingredients (APIs) in solvents across a broad range of polarities. The ability of COSMO-RS to predict and quantify the effects of solvent on crystal growth and morphology is assessed using hierarchical clustering to classify the solvents according to their overall interaction strength with the crystal faces. The COSMO-RS approach allows for a physical interpretation of the predictions in terms of surface polarity and is confirmed by comparison to published experimental data. Herein a methodology is reported for automated computation of the activity coefficients of all solvent-surface pairs directly from the drug crystal structure. The procedure goes beyond the traditional trial-and-error solvent selection process and has the potential to be used as a rapid computational screening tool in pharmaceutical drug development.

Research Progress on Structure and Property of Hybrid Organic-Inorganic Perovskite

This research briefly introduces the research background, structure, properties and application fields of perovskite, and reviews the research progress of hybrid organic-inorganic perovskite in recent years. The effects of crystal structure and organic cations on the stability, thermal conductivity, carrier mobility and optical and electrical properties of the hybrid perovskite are summarized, with which the importance of controlled crystal growth is highlighted and the current preparation methods and new preparation processes of perovskite materials are concluded. Finally, a prospection of perovskite materials and their applications is put forward, which provides a theoretical understanding for new perovskite materials with better crystal growth and crystal face control in the future, so as to promote the development of perovskite solar cells, light energy devices and other related fields.

Crystallization kinetics, morphology and spherulite growth in poly(trimethylene terephthalate) modified with bisphenol-A diglycidyl ether

The role of bisphenol-A diglycidyl ether (BADGE)—a weakly interacting, low molecular weight additive on crystallization kinetics, morphology and spherulite growth of semi-crystalline thermoplastic- poly(trimethylene terephthalate) (PTT) is quantitatively evaluated. Blends of PTT with different loadings of BADGE were prepared by melt blending. Weak secondary interactions between BADGE and PTT influenced the crystallization kinetics of PTT. This gives rise to concentration-dependent changes in spherulite morphology, crystallization kinetics and stereochemical conformation of PTT. BADGE behaved as a nucleating agent/plasticizer for PTT depending on its loading and changed the conformational distribution of PTT thereby facilitating chain mobility, along with diffusion and attachment of chain segments to crystal nuclei and growth faces. Crystallization kinetics and glass transition studies were carried out using differential scanning calorimetry, while spherulite growth rate was followed using polarized optical microscope equipped with hot stage, and the microphase structure evaluated using small-angle X-ray scattering studies.

Controllable crystallization of urea crystal face (0 0 1) by molecular simulation

Crystal regulation including crystal habit and size regulation is of considerable significance in chemical and pharmaceutical industry. Here urea is used as a typical crystal model, because crystal formation of urea is simple and its traditional crystallization is uncontrollable. Therefore, we adopted molecular dynamics simulation to study the crystal-solution interface during the urea crystal growth. And the regulation mechanism of additive on urea crystal growth was further revealed by analyzing the adsorption energy, density profile, diffusion coefficient, number of contact and H-bond interaction of four additives (trehalose, sorbitol, glucose, and l-lysine) on the crystal face (0 0 1). The results indicated that to some extent, those additives can do inhibit the growth of urea crystal face (0 0 1) at 1 atm and 290 K. The more negative adsorption energy of the additive on crystal face (0 0 1) can lead to the better inhibitive efficiency. And the trehalose is one of the best inhibitors for the growth of crystal face (0 0 1). The type and number of the polar group carried by additives determine their regulation capability.

The effect of crystal-solvent interaction on crystal growth and morphology

Diacetone diperoxide (DADP)/1,3,5-tribromo-2,4,6-trinitrobenzen (TBTNB) and diacetone diperoxide (DADP)/1,3,5-trichloro-2,4,6-trinitrobenzen (TCTNB) cocrystals were selected to reveal the effect of interaction at solvent-crystal interface on crystal growth and morphology, and analyze the interaction at the interface by molecular electrostatic potentials (ESP), mass density distribution and radial distribution function (RDF). It can be found that in DADP/TBTNB-acetonitrile interface model, the interaction at (0 2 0) face is the greatest and presents as repulsive interaction, so the growth rate of (0 2 0) face is the largest and the (0 2 0) face is the smallest. Conversely, the least and attractive interaction at interface tends to make (1 1 −1) to be the largest. These deductions are in accordance with the simulation of DADP/TBTNB cocrystal morphology in acetonitrile, and similar conclusion also can be obtained from the growth of DADP/TBTNB cocrystal in cyclohexanone. These are related to cavities of cocrystal face, which affect the distribution and orientation of solvent molecules. It can be reasoned out that the quantity of cavities on crystal face and the electrophilicity or nucleophilicity of solvent molecules may inhibit or facilitate the growth of crystal face.

Electrochemical degradation of fluoxetine on nanotube array intercalated anode with enhanced electronic transport and hydroxyl radical production

TiO2 nanotube array intercalated anode (Ti/TNAs∗/PbO2) was successfully fabricated by anodic oxidation of Ti sheet and electro-deposition of PbO2. The Ti/TNAs∗/PbO2 anode was demonstrated high electrochemical activity for the degradation of fluoxetine (FLX) in water. In the batch experiment, 97.2% FLX was removed in 10 min, and the microbial toxicity of FLX solution towards Vibrio fischeri decreased from 41.2% to 2.2% in 30 min. The impressive performance of Ti/TNAs∗/PbO2 is attributed to the optimized electronic transport perpendicular to the anode, and the enhanced hydroxyl radical (OH) yield induced by modified PbO2 crystal face growth. FLX molecular is underwent a mass attack by OH, and rapidly mineralized to CO2 and H2O. The degradation mechanism of FLX was verified by the analyses of mass spectrometry, electron spin resonance (ESR) spectrometry, and electrochemical measure. A sequential process combined pre-concentration with electrochemical oxidation using Ti/TNAs∗/PbO2 anode was set up for the treatment of FLX contaminated simulated wastewater. During continuously 120 h experiment, the removal efficiencies of FLX and TOC remained as high as 94.3% and 83.1%, and the microbial toxicity was disappeared in the effluent all the time.

A Highly Conserved Motif within the Amelotin Protein Controls the Surface Growth of Brushite

Amelotin (AMTN) protein exerts a direct role on enamel biomineralization likely due to its binding affinity with calcium phosphates (Ca-Ps). However, the kinetics and molecular mechanisms of the AMTN–Ca-P interaction remain largely unknown. Here we used in situ atomic force microscopy (AFM) to directly image the surface growth of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO4·2H2O) in the presence of recombinant human AMTN. Measured step movement velocities of the DCPD (010) face show that AMTN protein promotes crystal face growth only within a limited concentration range, whereas inhibition occurs outside of this range. A peptide derived from a highly conserved and potentially phosphorylated motif (SSEEL) within the AMTN protein inhibits crystal growth similar to that of the AMTN protein at low concentration. By the use of single-molecule force spectroscopy (SMFS), we directly measure the binding of the full-length AMTN and SSEEL to the DCPD (010) face. Similar rupture forces reveal that this acti...

Optimizing the Crystal Habit of Glycine by Using an Additive for Impinging Jet Crystallization

AbstractAdditives selectively inhibit or enhance the growth of crystal faces and effectively change the crystal morphology. For the first time, potassium chloride was used as additive during impinging jet crystallization of glycine. The structure of the powder particles was evaluated by X‐ray powder diffraction, differential scanning calorimetry, scanning electron microscopy with energy dispersive X‐ray spectroscopy, headspace gas chromatography, and flame atomic absorption spectrometry. Even a minor amount of KCl had a significant effect on the crystal roundness and reduced the particle size significantly, despite of the extremely rapid nature of the crystallization process. This method resulted in the α‐polymorph of glycine with an appropriate low residual additive content and a minimal residual organic solvent content. The arrangement and the optimal concentration of the additive were determined.

Growth of Crystal Faces Enhanced by 3D Nuclei Deposition: A Monte Carlo Simulation

In general, crystal growth proceeds by the addition of growth units at steps originating from dislocations or 2D nuclei. However, evidence exists that small 3D nuclei deposited on crystal faces can also act as step sources. In this study, the Monte Carlo method, based on the Kossel model, is used to study the fates of 3D nuclei adsorbed on planar and stepped crystal surfaces. For equilibrium, Δμ/kT = 0, the nuclei dissolve completely, regardless of size. For supersaturated solutions, Δμ/kT > 0, the upper parts of the nuclei dissolve, while the lower parts act as a source of steps expanding over the surface. This results in flat topped growth islands, the slope of which side faces increases for increasing nucleus size and supersaturation and decreasing bond strength. Growth on stepped surfaces leads to the formation of approximately circular plateaus, the width of which increases with decreasing substrate slope. Upon continued growth, these plateaus evolve into bunched step patterns. The Monte Carlo simula...

The solvent effect on the crystal morphology of two tegafur polymorphs

Pharmaceutical compounds are mostly produced in defined crystalline forms that are usually crystallized from solutions. Polymorphs, different crystalline phases of the same pharmaceutical compound, usually have different, precisely known dissolution rates and bioavailability, but crystal size and shape can affect these properties. Therefore, the crystal shape is monitored during the drug manufacturing process and a lot of work in the area of crystal engineering has been devoted to crystal habit control [1]. The crystallization solvent can have a significant effect on the resulting crystal shape; therefore solvent effect on crystal habit needs comprehensive studies. The compound studied in this research – tegafur (5-fluoro-1-(tetrahydro-2-furyl)-uracil) – is an antitumor agent, known to exist in α, β, γ, δ and ε polymorphs [2, 3]. Single crystal X-ray diffraction (SC XRD) was used to index crystal faces of α and β tegafur crystals grown in different solvents and molecular dynamics (MD) simulation was used as a tool to estimate the crystal face growth rates in several solvents. SC XRD results indicated that {011} and {110} faces dominated in β tegafur crystals when crystallized from ethanol, methanol, butyl acetate, tetrahydrofuran, whereas α tegafur crystals had a dominant {001}, {010} and {011} faces when crystallized from these solvents. Crystals grown in acetone had a different dominant faces for both polymorphs. The interaction between the solvents and each tegafur face was different, but the order of binding energy on these surfaces remained the same and was {011} > {110} > {010} for β tegafur and {001} > {011} > {010} for α tegafur. The analysis of MD data revealed that the system's primary interactions are weak hydrogen bonds. The achieved predictions were in agreement with experimental results. This work has been supported by the European Social Fund within the project «Support for Doctoral Studies at University of Latvia».

Molecular recognition of methyl α-D-mannopyranoside by antifreeze (glyco)proteins.

Antifreeze proteins and glycoproteins [AF(G)Ps] have been well-known for more than three decades for their ability to inhibit the growth and recrystallization of ice through binding to specific ice crystal faces, and they show remarkable structural compatibility with specific ice crystal faces. Here, we show that the crystal growth faces of methyl α-d-mannopyranoside (MDM), a representative pyranose sugar, also show noteworthy structural compatibility with the known periodicities of AF(G)Ps. We selected fish AFGPs (AFGP8, AFGP1–5), and a beetle AFP (DAFP1) with increasing antifreeze activity as potential additives for controlling MDM crystal growth. Similar to their effects on ice growth, the AF(G)Ps can inhibit MDM crystal growth and recrystallization, and more significantly, the effectiveness for the AF(G)Ps are well correlated with their antifreeze activity. MDM crystals grown in the presence of AF(G)Ps are smaller and have better defined shapes and are of higher quality as indicated by single crystal X-ray diffraction and polarized microscopy than control crystals, but no new polymorphs of MDM were identified by single crystal X-ray diffraction, solid-state NMR, and attenuated total reflectance infrared spectroscopy. The observed changes in the average sizes of the MDM crystals can be related to the changes in the number of the MDM nuclei in the presence of the AF(G)Ps. The critical free energy change differences of the MDM nucleation in the absence and presence of the additives were calculated. These values are close to those of the ice nucleation in the presence of AF(G)Ps suggesting similar interactions are involved in the molecular recognition of MDM by the AF(G)Ps. To our knowledge this is the first report where AF(G)Ps have been used to control crystal growth of carbohydrates and on AFGPs controlling non-ice-like crystals. Our finding suggests MDM might be a possible alternative to ice for studying the detailed mechanism of AF(G)P–crystal interactions. The relationships between AF(G)Ps and carbohydrate binding proteins are also discussed. The structural compatibility between AF(G)Ps and growing crystal faces demonstrated herein adds to the repertoire of molecular recognition by AF(G)Ps, which may have potential applications in the sugar, food, pharmaceutical, and materials industries.

Simulated rhythmic growth of targeted single crystal by polymer phase-field model

The novel phase field model with the “polymer characteristic” was established based on a nonconserved spatiotemporal Ginzburg–Landau equation TDGL model. Especially, we related the parameters of crystal temperature with the TDGL model. Moreover, the diffusion equations were discretized according to the diffusion coefficient of every lattice site in various crystal growth faces, and the shape of lattice was selected based on the real proportion of the unit cell dimensions. Spatiotemporal growth of stripped single crystals during isochronous decoration has been investigated theoretically based on this phase field model. Two dimensional numerical calculations were performed to elucidate the faceted single crystal growth including the stripped lozenge-shaped and hexagonal single crystals. Our simulated patterns were in good agreement with the experimental morphologies, and the physical origin of polymer single crystal growth was discussed.

The role of hydration and complexing in the mechanism of impurity influence on crystal growth

The influence of impurities of chlorides and nitrates of divalent Ca2+ and Ba2+ cations on the kinetic growth of potassium dihydrophosphate KH2PO4 crystals at a saturation temperature of 323 K and relative supersaturation of 0.03 has been investigated experimentally. It is established that the impurity acts differently, depending on the face index, the impurity concentration, cation hydration, and the stability of the complexes formed in the solution by impurity salt ions. A model is proposed to explain the different influence of impurity ions on the growth of crystal faces. This influence is determined by the different hydration of cations and enhanced association of cations and anions of impurity salts in the surface layer with a lower dielectric constant.

Circular Dichroism Tensor of a Triarylmethyl Propeller in Sodium Chlorate Crystals

In 1919, Perucca reported anomalous optical rotatory dispersion from chiral NaClO(3) crystals that were colored by having been grown from a solution containing an equilibrium racemic mixture of a triarylmethane dye (Perucca, E. Nuovo Cimento 1919, 18, 112-154). Perucca's chiroptical observations are apparently consistent with a resolution of the propeller-shaped dye molecules by NaClO(3) crystals. This implies that Perucca achieved the first enantioselective adsorption of a racemic mixture on an inorganic crystal, providing evidence of the resolution of a triarylmethyl propeller compound lacking bulky ortho substituents. Following the earlier report, NaClO(3) crystals dyed with aniline blue are described herein. The rich linear optical properties of (001), (110), and (111) sections of these mixed crystals are described via their absorbance spectra in polarized light as well as images related to linear dichroism, linear birefringence, circular dichroism, and anomalous circular extinction. The linear dichroism fixes the transition electric dipole moments in the aromatic plane with respect to the growth faces of the NaClO(3) cubes. Likewise, circular dichroism measurements of four orientations of aniline blue in NaClO(3) fix a bisignate tensor with respect to the crystal growth faces. Electronic transition moments and circular dichroism tensors were computed ab initio for aniline blue. These calculations, in conjunction with the crystal-optical properties, establish a consistent mixed-crystal model. The nature of the circular extinction depends upon the crystallographic direction along which the crystals are examined. Along 100, the crystals evidence circular dichroism. Along 110, the crystals evidence mainly anomalous circular extinction. These two properties, while measured by the differential transmission of left and right circularly polarized light, are easily distinguished in their transformation properties with respect to reorientations of the sample plates. Circular dichroism is symmetric with respect to the wave vector, whereas anomalous circular extinction is antisymmetric. Analysis of Perucca's raw data reveals that he was observing a convolution of linear and circular optical properties. The relatively large circular dichroism should in principle establish the absolute configuration of the propeller-shaped molecules associated with d- or l-NaClO(3) crystals. However, this determination was not as straightforward as it appeared at the outset. In the solid state, unlike in solution, a strong chiroptical response is not in and of itself evidence of enantiomeric resolution. It is shown how it is possible to have a poor resolution-even an equal population of P and M propellers-within a given chiral NaClO(3) crystal and still have a large circular dichroism.

Enzymatic degradation of poly(octamethylene suberate) lamellar crystals

Enzymatic degradation of poly(octamethylene suberate) single crystals was investigated by electron microscopy. Different lamellar morphologies were obtained using 2.5-hexanediol as a solvent and at a temperature between 42 and 51 °C. Crystals with a different degree of truncation and with monolayer or bilayer organization were analyzed. Lipases from Rhizopus oryzae were found to be highly effective in degrading crystalline domains and showed different attack mechanisms. Thus, enzymes preferentially attacked the lateral crystal growth faces or the lamellar fold surfaces depending on the crystallization conditions. Temperature and indeed its fluctuation during the crystallization process were crucial to determine how degradation started and progressed. The most interesting results were obtained for single crystals characterized by a low degree of truncation and formed in crystallization baths with a small temperature oscillation. In this case, it was shown that degradation started on the folding surface of specific sectors and progressed along a preferred crystal direction.

Simulated morphological landscape of polymer single crystals by phase field model

The novel phase field model with the "polymer characteristic" was established based on a nonconserved spatiotemporal Ginzburg-Landau equation (TDGL model A). Especially, we relate the diffusion equation with the crystal growth faces of polymer single crystals. Namely, the diffusion equations are discretized according to the diffusion coefficient of every lattice site in various crystal growth faces and the shape of lattice is selected based on the real proportion of the unit cell dimensions. Spatiotemporal growth of syndiotactic polypropylene single crystals during isothermal crystallization has been investigated theoretically based on this phase field model. Two dimensional numerical calculations are performed to elucidate the faceted single crystal growth including square, rectangular, lozenge-shaped, and hexagonal single crystals. Our simulated patterns are in good agreement with the experimental morphologies, and the physical origin of polymer single crystal growth is discussed.

Single crystal morphology and structural data of a series of polyesters derived from 1,8-octanediol

The morphology of solution grown single crystals of a series of polyesters derived from 1,8-octanediol and either an even or an odd dicarboxylic acid has been investigated. Different crystallization conditions (solvent and temperature) were tested for these polyesters whose dicarboxylate unit varied from pimelate to sebacate. Crystals showed a lozenge morphology with a degree of truncation which for a given solvent changed with the crystallization temperature. Curvature of growth faces, striations on the lamellar surface and a bilayered morphology were features that were observed in some cases. Polyethylene decoration highlighted a crystal sectorization and suggested a molecular folding parallel to the crystal growth faces. The studied polyesters always showed a single crystalline structure, according to electron and X-ray diffraction data. A practically all trans molecular conformation could always be deduced. Unit cell geometry changed from orthorhombic to monoclinic and the molecular content was variable in the studied series (two or four molecular segments). Lamellae gave rise to well-defined electron diffraction patterns that allowed the setting angle of molecular segments to be determined. A good agreement between simulated and experimental hk0 diffraction patterns was always found. Packing along the chain axis direction was completely defined for the sebacate derivative.