Control Of Crystal Morphology Research Articles

Wettability of Magnetite Nanoparticles Guides Growth from Stabilized Amorphous Ferrihydrite.

Crystal formation via amorphous precursors is a long-sought-after gateway to engineer nanoparticles with well-controlled size and morphology. Biomineralizing organisms, like magnetotactic bacteria, follow such a nonclassical crystallization pathway to produce magnetite nanoparticles with sophistication unmatched by synthetic efforts at ambient conditions. Here, using in situ small-angle X-ray scattering, we demonstrate how the addition of poly(arginine) in the synthetic formation of magnetite nanoparticles induces a biomineralization-reminiscent pathway. The addition of poly(arginine) stabilizes an amorphous ferrihydrite precursor, shifting the magnetite formation pathway from thermodynamic to kinetic control. Altering the energetic landscape of magnetite formation by catalyzing the pH-dependent precursor attachment, we tune magnetite nanoparticle size continuously, exceeding sizes observed in magnetotactic bacteria. This mechanistic shift we uncover here further allows for crystal morphology control by adjusting the pH-dependent interfacial interaction between liquidlike ferrihydrite and nascent magnetite nanoparticles, establishing a new strategy to control nanoparticle morphology. Synthesizing compact single crystals at wetting conditions and unique semicontinuous single-crystalline nanoparticles at dewetting conditions in combination with an improved control over magnetite crystallite size, we demonstrate the versatility of bio-inspired, kinetically controlled nanoparticle formation pathways.

Crystal morphology control of synthetic giniite for enhanced photo-Fenton activity against the emerging pollutant metronidazole

Metronidazole (MNZ) is a recalcitrant antibiotic with toxic and carcinogenic effects in aquatic environments. In this work, Fe5(PO4)4(OH)3·2H2O (giniite) particles were synthesised with three different alkaline cations (Li+, Na+ and K+) and used as Fenton catalysts for MNZ removal. It is shown that the addition of different cations during the hydrothermal synthesis process promote different morphologies from asterisk-like to flower-like and branches-like, maintaining the crystalline structure of pure giniite. The photo-Fenton activity of these particles was then evaluated through the degradation of MNZ under sunlight radiation for 9 h. The results indicate that the alkaline cation has a predominant role in the photo-Fenton efficiency, as demonstrated by the superior degradation efficiencies of Na@giniite particles (91.2% and 72.5% with giniite concentration of 0.2 g L−1 and 0.07 g L−1, respectively), related with its high surface area (10.7 m2 g−1). Thus, it is demonstrated the suitability of Na@giniite particles as Fenton catalyst for MNZ removal from water.

Morphology Regulation of Monosodium Urate Monohydrate Crystals via Fabricated Uniform Hydrogel Slices

AbstractCrystal morphology control is a common concern for the crystal engineering and relevant applications. For example, urate crystallization is important for the study of the hyperuricemia induced gout. Herein, biomimetic hydrogel material with uniform surface and vertical structure is fabricated, which possesses hybrid pH‐temperature responsibility for high‐efficiency interfacial nucleation and concentration regulation functions. The developed hydrogel layers are prepared to slice type as a functional microplatform and then added into the uric acid dihydrate (UAD) crystal solution to induce monosodium urate monohydrate (MSUM) crystallization. With different dosage of the hydrogel slices (HGS) in the solution, diverse crystal morphologies can be obtained in an efficient manner, such as “flower,” “sphere,” “sticky spheres,” which entirely distinguishes from the one prepared via no‐HGS. This work explores a new path for revealing the relevant crystallization mechanism and developing crystal morphology control technology with hydrogel interfacial materials.

Solubility and dissolution thermodynamic properties of L-carnosine in binary solvent mixtures

Thermodynamic data are the basis for design of crystallization process and control of crystal morphology and polymorph. In this work, solubility data of L-carnosine in different binary solvent mixtures, including water + (methanol, isopropanol or acetone), were determined in temperatures ranging from 288.05 K to 323.15 K by static method under atmospheric pressure. It was found that the solubility data of L-carnosine decrease apparently with the increasing of the mole fraction of organic solvent in binary solvent mixtures and increase with the rising of temperature. In addition, the experimental solubility data were correlated and analyzed by the modified Apelblat equation, the NRTL model and the Jouyban–Acree model to extend the applicability of the solubility data. Finally, the standard dissolution thermodynamic properties, including Gibbs energy, entropy and enthalpy were calculated and discussed based on the experimental solubility data and Van’t Hoff equation.

Investigation on Three Dimensional Hybrid Organic–Inorganic β-ZnTe(en)0.5 Flowerlike Structures and Corresponding Mesoporous PbTe Flowerlike Microcrystals

Three dimensional (3D) metal tellurides have a broad range of applications, but their template preparation technology is limited by the preferentially formed one dimensional tellurium materials. Here, the hybrid organic–inorganic 3D β-ZnTe(en)0.5 flowerlike microcrystals, which are synthesized by a simple and reproducible method, are used as templates to prepare 3D mesoporous PbTe flowerlike microcrystals through ion-exchange route. The growth mechanism of β-ZnTe(en)0.5 and mesoporous PbTe flowerlike structures are discussed in detail. Firstly, because the binding capacity of Zn2+ ions with Te2− ions and ethylenediamine (EN) molecules is in preference to Te–Te atoms, 3D β-ZnTe(en)0.5 flowerlike microcrystals are formed instead of 1D Te nanorods. During this process, the amount of EN not only play a key role in the control of crystal morphology, but also influence the crystal structure. Secondly, mesoporous PbTe flowerlike microcrystals are formed since Pb2+ ions incompletely occupied the space created by the loss of EN molecules and Zn2+ ions in orthorhombic β-ZnTe(en)0.5 flowerlike templates.

Control over Crystal Size in Vapor Deposited Metal-Halide Perovskite Films.

Understanding and controlling grain growth in metal halide perovskite polycrystalline thin films is an important step in improving the performance of perovskite solar cells. We demonstrate accurate control of crystallite size in CH3NH3PbI3 thin films by regulating substrate temperature during vacuum co-deposition of inorganic (PbI2) and organic (CH3NH3I) precursors. Films co-deposited onto a cold (−2 °C) substrate exhibited large, micrometer-sized crystal grains, while films that formed at room temperature (23 °C) only produced grains of 100 nm extent. We isolated the effects of substrate temperature on crystal growth by developing a new method to control sublimation of the organic precursor, and CH3NH3PbI3 solar cells deposited in this way yielded a power conversion efficiency of up to 18.2%. Furthermore, we found substrate temperature directly affects the adsorption rate of CH3NH3I, thus impacting crystal formation and hence solar cell device performance via changes to the conversion rate of PbI2 to CH3NH3PbI3 and stoichiometry. These findings offer new routes to developing efficient solar cells through reproducible control of crystal morphology and composition.

Microfluidic strategy for rapid and high-quality control of crystal morphology of explosives

A new strategy based on a microfluidic platform is proposed for the rapid and high-quality control of explosives' crystal morphology.

Fine control of crystal morphologies of all-silica DDR in ethylenediamine-free gel with inorganic base as mineralizing agent

Abstract The size and morphology control of zeolite crystals is important which might have significant impact on their adsorption, separation and catalytic properties. Traditional hydrothermal synthesis of zeolite DDR usually yields big diamond-shaped crystals and there are few reports about its size and morphology control. In this study, microwave synthesis of all-silica DDR zeolite was systematically studied with 1-adamantane amine as template and inorganic base as mineralizing agent (KOH, NaOH and LiOH). The use of co-solvent (ethylenediamine) and fluorides were avoided which is environment-friendly. The use of inorganic bases also reduced synthesis cost. High quality micron sized DDR crystals with high yield were obtained in only a few hours which is the synergy of microwave heating and seeding, both are powerful methods on reducing synthesis time. A rich variety of crystal morphologies, like diamond, bipyramid, hexagonal prism and sphere, were obtained which can be controlled by the addition of metal cations, gel alkalinity, synthesis temperature and gel dilution. 29 Si NMR, FT-IR and nitrogen adsorption confirmed the formation of zeolite framework and its porosity. The fine control of crystal size and morphology of DDR zeolite may facilitate its application in adsorption, membrane separation and catalysis.

Insight into the effect of maleic acid on the preparation of α-hemihydrate gypsum from phosphogypsum in Na2SO4 solution

The control of crystal morphology is crucial to preparation of α-hemihydrate gypsum (α-HH). α-HH was prepared from phosphogypsum (PG) in Na2SO4 solution at different temperatures. The effect of maleic acid (C4H4O4) on the dehydration rate and growth behavior of α-HH was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), and the interactions of C4H4O4 molecule with the α-HH surface were studied using density functional theory (DFT) calculations. The results show that the increase in Na2SO4 concentration and solution temperature can shorten the dehydration time of PG. Maleic acid inhibits the conversion of PG to α-HH by prolonging the crystal growth period. α-HH crystals prefer to grow along the c-axis and present a long columnar crystal. With an increase in the maleic acid concentration from 0.00 to 5.76 mM, the morphology of α-HH evolves from a needle-like whisker to a short equiaxial crystal, and the corresponding aspect ratio decreases from 14.19 to 0.91. The calculation results indicate that the strong interactions between the C4H4O4 molecule and the (1 1 1) crystal plane of α-HH are largely attributable to the bonding of both the single-bond oxygen (O1) and double-bond oxygen (O2) in C4H4O4 with the Ca atoms of the (1 1 1) crystal plane and that the chemisorption of C4H4O4 can occur on the (1 1 1) crystal plane with the lowest adsorption energy of −201.65 kJ/mol. C4H4O4 adsorption on the (1 1 0) crystal plane is through a single O2Ca bond with an adsorption energy of −95.32 kJ/mol. The interaction between the (0 1 0) crystal plane and C4H4O4 is weak. It can be concluded that maleic acid can preferentially adsorb on the (1 1 1) crystal plane and retard crystal growth along the c-axis during the preparation of α-HH from PG.

Enhancing the solubility and bioavailability of poorly water-soluble drugs using supercritical antisolvent (SAS) process

Poor water solubility and poor bioavailability are problems with many pharmaceuticals. Increasing surface area by micronization is an effective strategy to overcome these problems, but conventional techniques often utilize solvents and harsh processing, which restricts their use. Newer, green technologies, such as supercritical fluid (SCF)-assisted particle formation, can produce solvent-free products under relatively mild conditions, offering many advantages over conventional methods. The antisolvent properties of the SCFs used for microparticle and nanoparticle formation have generated great interest in recent years, because the kinetics of the precipitation process and morphologies of the particles can be accurately controlled. The characteristics of the supercritical antisolvent (SAS) technique make it an ideal tool for enhancing the solubility and bioavailability of poorly water-soluble drugs. This review article focuses on SCFs and their properties, as well as the fundamentals of overcoming poorly water-soluble drug properties by micronization, crystal morphology control, and formation of composite solid dispersion nanoparticles with polymers and/or surfactants. This article also presents an overview of the main aspects of the SAS-assisted particle precipitation process, its mechanism, and parameters, as well as our own experiences, recent advances, and trends in development.

Crystal Morphology Control of Synthetic Giniite by Alkaline Cations and pH Variations

The synthetic analogue of the mineral giniite is a promising material for capture of phosphopeptides from complex tryptic digests, photocatalysis, and cathode for lithium battery applications. In all these applications, the crystal morphology of giniite shows to be extremely important, however, the reported synthesis and crystal morphologies are scattered among a variety of approaches. Here we report a hydrothermal synthesis that allows achieving five different morphologies of giniite only by changing the pH by addition of three different alkaline cations (Na+, Li+, and K+) in the form of hydroxides. At pH 2, micrometric sphere-like assemblies of nanoparticles were obtained. At pH 4, fractal dendritic crystals as well as intergrown flower-like and asterisk-like crystals were synthesized. At pH 6, the synthesis resulted in dagger-like crystals of dissolved dendritic structures.

Continuous Crystallization of Proteins in a Stirred Classified Product Removal Tank with a Tubular Reactor in Bypass

A lab-scale stirred tank with a cooled tubular reactor in bypass was applied for continuous crystallization of lysozyme and a full-length therapeutic monoclonal antibody. The stirred tank was operated as a mixed suspension classified product removal crystallizer. Lysozyme was crystallized by a combination of cooling crystallization and salting-out. The antibody was crystallized by a combination of cooling crystallization and isoelectric crystallization. It was deduced that nucleation rates were enhanced when the protein solutions passed through the cooled tubular bypass. It was further deduced that crystal growth rates were enhanced in the stirred tank which was operated at a higher temperature compared to the tubular reactor. Classified product removal was possible by controlled sedimentation of protein crystals. The continuous crystallization system allowed a targeted control of crystal morphology and size. No sedimentation occurred in the tubular reactor and precipitation was avoided at all times. High...

Computational Simulations of Morphological Transformations by Surface Structures: The Case of Rutile TiO2 phase

Computational simulations based on periodic density functional theory have been carried out to investigate the control of crystal morphology by accurate values of surface energies by Wulff theorem. This method can be used as a very useful tool for the design and knowledge of synthesis of new materials. In a special case, rutile TiO2 phase, exhibits great variety of morphologies and properties making this system an interesting target for this approach. The low index, (100), (001), (101), (110), (111) surfaces were modeled and the respective surface energies produces the follows stability order: (110) < (010) < (101) < (001) < (111). The map of some morphologies routes was constructed from the calculated energies as a starting point without environmental influence and can be used to elucidate the influence of chemical routes. This method has helped in the knowledge of morphological modifications as a function of synthesis environment besides the connection between system characteristics and the exposed surfaces.

Control of crystal morphology and its effect on electromechanical performances of electrostrictive P(VDF-TrFE-CTFE) terpolymer

Interplay of microstructure and electromechanical properties of the poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer were studied by tailor-made adjusting crystal fraction via temperature annealing processing. Worm-like crystal nanodomain firstly demonstrated an evolution of the surface morphology upon the increasing temperature annealing treatment, in favor of preferential crystal orientation, known to facilitate the dipoles switching along the external electric field. Apart from the aligned crystal orientation and high coverage of crystal fraction raised by high temperature annealing, the enhancement of interphase fraction of the terpolymer contributes to the high-performance of dielectric property and increases the electric breakdown strength as well. The electromechanical behaviors linking to the microstructure were finally evaluated by a bilaminar unimorph cantilever beam theory. And consequently the figure of merits of electromechanical performance, namely dielectric constant and tensile strength values play a trade-off role in the field-induced strain of the electroactive terpolymer layer, suggesting the microstructure-controlled effects. The tip displacement of bilaminar cantilever beam, serving as an indicator of the actuator performance, consists in the electroactive terpolymer layers and passive foil support. Aiming at obtaining optimum actuator device, specific microstructure of terpolymer membrane was revealed by taking the passive support layers into consideration.

Mutual diffusion diagram of liquid-liquid interfaces for morphological control of NaCl crystals

Liquid-liquid interfacial crystallization requires mutual diffusion between two liquids to drive the crystallization. Understanding mass transfer between two liquids is important for achieving sophisticated morphological control. In this work, the effect of mutual diffusion on crystal morphology was examined by calculating the solute concentration near the interface. NaCl crystals were prepared with various organic solvents. The crystal shape, amount of precipitation, and particle size were evaluated. The diffusion rate in each organic solvent was measured from the time evolution of the surface area and the volume of the droplet. The solute concentration and the supersaturation ratio near the interface were calculated by Fick's law. The change in crystal morphology revealed that either nucleation or crystal growth preferentially occurred depending on the organic solvent. The magnitude of the water diffusion rate affected the crystal morphology. The dependence of the crystal morphology on the organic solvent was also determined by the diffusion coefficient and the mutual solubility. These results provide new insight into our understanding of the mutual diffusion at liquid-liquid interfaces and the development of crystal morphology control.

Solvothermal Synthesis of LiFePO4 with an Energy Saving Technique

Lithium iron phosphate (LiFePO4) with stable olivine structure is considered as a promising cathode material for rechargeable lithium batteries, due to its nontoxicity, high specific electrochemical capacity, excellent cycling stability and low cost. The LiFePO4, however, suffers from low power capacity attributed to its low electronic conductivity (about 10-9 S cm-1) and low ionic conductivity(about 1.8×10-14 cm2 S-1). Various approaches have been investigated to improve its electronic conductivity, such as carbon coating, higher valent cation doping, etc. Because of lithium ion’s one dimensional migration channel parallel to the b axis reducing particle sizes and crystal morphology control have been confirmed as the effective ways to improve LiFePO4 performances. Compared with conventional solid-phase synthesis method, hydrothermal/ solvothermal synthesis methods have shown advantages in controlling particle size and crystal orientation in synthesizing many materials including LiFePO4. hydrothermal/solvothermal synthesis technique is more complicated and more sensitive to reaction parameters compared with solid-phase method. Reaction parameters like feeding sequence, temperature and time have great influences on product LiFePO4’s crystallinity, morphology and especially electrochemical performances. As investigated ethylene glycol(EG) as a solvent or co-solvent have significant positive influences (for smaller crystal size and better electrochemical performance) on LiFePO4solvothermal process. In this work, we have applied a solvothermal process using ethylene glycol(EG) as solvent to investigate LiFePO4 crystallization. The synthesis of LiFePO4 was carried out in a 50ml Teflon vessel, which was sealed in a stainless-steel autoclave. The molar ration of Li:Fe:P in the precursor solution was 2.7:1:1, and the concentration of LiFePO4 in the reaction solution was controlled to be 0.2M. LiOH·H2O, FeSO4·7H2O and H3PO4 were chosen as Li, Fe, P sources, and EG was chosen as solvent for this solvothermal synthesis. The typical feeding sequence was chosen:. The reactor was heated in an air oven setting at 120, 140, 160, 180˚C for 1min. The heating and cooling rates were measured and collected. Fig. 1 shows the comparison of the temperature in and out of Teflon when air oven is set as 160 ˚C for 1min. The temperature of air in oven increased faster than the slurry in reactors. When oven was set at 160˚C for 1min,the highest temperature of the slurry is 89˚C instead. The result samples were characterized by XRD shown in Fig. 2. Crystallized LiFePO4 phase appeared associated with little Fe3(PO4)2·H2O and Li3PO4 when oven temperature was set at 160 ˚C for 1min. It indicates that the LiFePO4 nuclei could be formed as low as 89˚C (real temperature) in EG during solvothermal process. Then we tried to synthesize LiFePO4 samples in 85 and 80 ˚C for 10 hours. The XRD results show that LiFePO4 crystal phase can be formed even at as low as 80 ˚C in EG while in water the lowest temperature for LiFePO4crystallization is 105 ˚C. The decrease of LiFePO4 crystallization temperature is attributed to EG’s unique properties. There are 2 hydroxyl groups in EG’s chemical formula which have a strong hydrogen bonding ability. The two hydrogen bonds are not formed in one plane which results in a loose bonding structure and produces a low energy intermediate during crystallization reaction. It indicates a catalytic effect on LiFePO4 crystallization. And EG has a smaller solubility compared with water which leads to a higher degree of supersaturation at the same raw material concentration. LiFePO4 nucleis with slow crystal growth from diffusing solvents are because of the lower viscosity of EG. The results of this work provide deep insights into LiFePO4 crystallization in solvothermal synthesis process. Also it provides the probability of synthesis materials for lithium ion batteries on an energy saving mode. Figure 1

Control of Crystal Morphology for Mold Flux During High-Aluminum AHSS Continuous Casting Process

In the present manuscript, the efforts to control the crystal morphology are carried out aiming at improving the lubrication of lime-alumina-based mold flux for casting advanced high-strength steel with high aluminum. Jackson α factors for crystals of melt crystallization in multi-component mold fluxes are established and reasonably evaluated by applying thermodynamic databases to understand the crystal morphology control both in lime-alumina-based and lime-silica-based mold fluxes. The results show that Jackson α factor and supercooling are the most critical factors to determine the crystal morphology in a mold flux. Crystals precipitating in mold fluxes appear with different morphologies due to their different Jackson α factors and are likely to be more faceted with higher Jackson α factor. In addition, there is a critical supercooling degree for crystal morphology dendritic transition. When the supercooling over the critical value, the crystals transform from faceted shape to dendritic ones in morphology as the kinetic roughening occurs. Typically, the critical supercooling degrees for cuspidine dendritic transition in the lime-silica-based mold fluxes are evaluated to be between 0.05 and 0.06. Finally, addition of a small amount of Li2O in the mold flux can increase the Jackson α factor and decrease the supercooling for cuspidine precipitation; thus, it is favorable to enhance a faceted cuspidine crystal.

One-pot synthesis of Pd@Pt core–shell nanocrystals for electrocatalysis: control of crystal morphology with polyoxometalate

Pt-based bimetallic nanocrystals (NCs) are an important class of catalytic materials especially in the area of energy conversion due to their outstanding catalytic performance. The catalytic function of Pt-based bimetallic NCs toward a specific catalysis reaction can be optimized by tailoring their surface structure, which can be realized through the precise control of the NC morphology. In the present work, we developed a facile one-pot polyoxometalate (POM)-mediated synthesis approach for the synthesis of Pt-based bimetallic NCs with controlled morphologies and fine crystal structures, and investigated the influence of their morphology on their catalytic function. Pd@Pt core–shell NCs with well-defined morphologies and controlled surface structures could be prepared by the simultaneous reduction of Pt and Pd precursors in the presence of a typical Keggin-type POM (H3PMo12O40) and ascorbic acid (AA). During the formation of NCs, the POMs served not only as a stabilizing agent but also a reducing agent. Notably, the presence of the POMs as well as the relative concentration of AA to metal precursors could afford fine control over the growth mode of the Pt shells on the Pd cores, and thus the final morphology of the Pd@Pt NCs. The prepared POM-passivated Pd@Pt NCs outperformed Pd@Pt NCs synthesized without the POMs as well as a commercial Pt/C catalyst for the electrooxidation of methanol, and their catalytic activity and stability distinctly depended on their Pt shell structure. We envision that this strategy will pave the way for the rational design of NC-based catalyst systems.

Stereo imaging of crystal growth

Significance A methodology that directly images the full three‐dimensional (3‐D) shape of crystals within a crystallizer is reported. It is based on the mathematical principle that if the two‐dimensional (2‐D) images of an object are obtained from two or more different angles, the full 3‐D crystal shape could be reconstructed. A prototype instrument is built and proof of concept study performed to demonstrate the potentials in using the system for 3‐D measurement of crystal shape and shape distribution. It is our belief that 3‐D measurement of crystal shape represents a significant step forward from existing work of 2‐D measurement of crystal morphology and is potentially of great significance to research toward closed‐loop control of crystal morphology. © 2015 American Institute of Chemical Engineers AIChE J, 62: 18–25, 2016

Control of Crystal Morphology and Size of Calcium Sulfate Whiskers in Aqueous HCl Solutions by Additives: Experimental and Molecular Dynamics Simulation Studies

The effect of cetyltrimethylammonium bromide (CTAB) on the crystal morphology and size of calcium sulfate whiskers in aqueous HCl solutions was investigated by combined experimental and molecular dynamics (MD) simulation studies. When CTAB was used, calcium sulfate whiskers with small diameters and high aspect ratios were obtained. The MD simulation results indicate that the experimental results can be attributed to the combined effect of the surface adsorption and inhibition of the solute diffusion of CTAB.