Formation Of Mixed Crystals Research Articles

The Rise in Tubular pH during Hypercalciuria Exacerbates Calcium Stone Formation.

In calcium nephrolithiasis (CaNL), most calcium kidney stones are identified as calcium oxalate (CaOx) with variable amounts of calcium phosphate (CaP), where CaP is found as the core component. The nucleation of CaP could be the first step of CaP+CaOx (mixed) stone formation. High urinary supersaturation of CaP due to hypercalciuria and an elevated urine pH have been described as the two main factors in the nucleation of CaP crystals. Our previous in vivo findings (in mice) show that transient receptor potential canonical type 3 (TRPC3)-mediated Ca2+ entry triggers a transepithelial Ca2+ flux to regulate proximal tubular (PT) luminal [Ca2+], and TRPC3-knockout (KO; -/-) mice exhibited moderate hypercalciuria and microcrystal formation at the loop of Henle (LOH). Therefore, we utilized TRPC3 KO mice and exposed them to both hypercalciuric [2% calcium gluconate (CaG) treatment] and alkalineuric conditions [0.08% acetazolamide (ACZ) treatment] to generate a CaNL phenotype. Our results revealed a significant CaP and mixed crystal formation in those treated KO mice (KOT) compared to their WT counterparts (WTT). Importantly, prolonged exposure to CaG and ACZ resulted in a further increase in crystal size for both treated groups (WTT and KOT), but the KOT mice crystal sizes were markedly larger. Moreover, kidney tissue sections of the KOT mice displayed a greater CaP and mixed microcrystal formation than the kidney sections of the WTT group, specifically in the outer and inner medullary and calyceal region; thus, a higher degree of calcifications and mixed calcium lithiasis in the kidneys of the KOT group was displayed. In our effort to find the Ca2+ signaling pathophysiology of PT cells, we found that PT cells from both treated groups (WTT and KOT) elicited a larger Ca2+ entry compared to the WT counterparts because of significant inhibition by the store-operated Ca2+ entry (SOCE) inhibitor, Pyr6. In the presence of both SOCE (Pyr6) and ROCE (receptor-operated Ca2+ entry) inhibitors (Pyr10), Ca2+ entry by WTT cells was moderately inhibited, suggesting that the Ca2+ and pH levels exerted sensitivity changes in response to ROCE and SOCE. An assessment of the gene expression profiles in the PT cells of WTT and KOT mice revealed a safeguarding effect of TRPC3 against detrimental processes (calcification, fibrosis, inflammation, and apoptosis) in the presence of higher pH and hypercalciuric conditions in mice. Together, these findings show that compromise in both the ROCE and SOCE mechanisms in the absence of TRPC3 under hypercalciuric plus higher tubular pH conditions results in higher CaP and mixed crystal formation and that TRPC3 is protective against those adverse effects.

Temperature-Dependent Mixing Behavior of Tristearin and 1,2-Distearoyl-3-oleoyl-rac-glycerol (SSO)

We explored the temperature-dependent polymorphism and thermal behavior of binary blends of the triacylglycerols tristearin (SSS) and 1,2-stearoyl-3-oleoyl-rac-glycerol (SSO). We created a kinetic phase diagram based on heating and cooling treatments from 80 to 20 °C at 1 °C/min and back. Under these conditions, SSS dominated SSO–SSS thermal behavior down to a mole fraction (XSSS) of 0.2. The presence of SSO at XSSO = 0.1 to 0.8 promoted the polymorphic transition of SSS from α to β, whereas SSS at XSSS = 0.1 to 0.7 enhanced the transition of SSO from double- and triple-chain length α-crystals to triple-chain length β′-crystals. Results showed that SSS was miscible in molten SSO in the metastable and stable polymorphs at all mole fractions studied. Finally, there was evidence of possible mixed crystal formation between SSO and SSS at XSSO = 0.2 to 0.9, for which we describe a number of possible causes. Outputs from this study provide further insights into the interactions of SSO and SSS as may occur during crystallization, fractionation, and product storage in fat-containing foods.

Coagulation of trace arsenic and cadmium from drinking water using titanium potassium oxalate

Coagulation is a simple and cost-effective water treatment method that does not work well in removing multiple cationic and anionic heavy metals simultaneously from drinking water. Titanium potassium oxalate (K2TiO(C2O4)2), a fur tanning reagent, was found to be able to efficiently remove arsenite (As(III)), arsenate (As(V)), and Cd simultaneously. A dose of 120 µmol/L K2TiO(C2O4)2 could remove more than 90% of As and Cd to meet the drinking water standards when their initial concentrations were 10 times their maximum concentration limits, whereas traditional coagulants, such as Fe2(SO4)3 and Al2(SO4)3, failed to meet the drinking water standards. Additionally, K2TiO(C2O4)2 coagulation consumes natural water hardness (Ca2+/Mg2+) to produce softer water and releases healthy K+ as a by-product. The mechanism study indicated that K2TiO(C2O4)2 reacted with natural calcium ions in drinking water to form calcium oxalate, while residual titanium was hydrolyzed with water to form hydrous titanium oxide. Arsenic was removed primarily via complexation with hydrous titanium oxide, while Cd was removed via the combined effect of adsorption by hydrous titanium oxide and mixed-crystal formation by calcium oxalate. This study provides an efficient coagulant for removing multiple heavy metals simultaneously, which can be applied in water treatment to provide safe and healthy drinking water.

Multicolor Photochromism of Two-Component Diarylethene Crystals Containing Oxidized and Unoxidized Benzothiophene Groups

Preparing mixed crystals composed of two or more components is one of the useful approaches to not only modifying the physical properties and chemical reactivity of molecular crystals but also creating their novel functionality. Here we report preparation and photoresponsive properties of two-component mixed crystals containing photochromic bis(benzothienyl)ethene derivatives that show different colors in the closed-ring forms depending on the oxidation state of the benzothiophene groups. The similarity in the molecular structures of the two diarylethenes, which are different from each other only in the oxidation state of the benzothiophene groups, allowed the formation of two-component mixed crystals by recrystallization from mixed solutions containing the two compounds. Irradiating the mixed crystals with light of appropriate wavelengths induced the selective photoisomerizaion of the two diarylethenes, leading to multicolor photochromic performance, such as colorless, orange, yellow, and red. Such molecular crystals with multiresponsive functions can find potential applications in multistate optical recording and multicolor displays. The present results demonstrate that combining differently oxidized diarylethene derivatives is an effective strategy for preparing multicomponent mixed crystals with finely tuned composition and desired photoresponsive properties.

Investigation of spectral properties of potassium-aluminum-borate glass with CuCl - CuBr nanocrystals

Heat treatment conditions effect on the characteristics of exciton absorption and luminescence of CuCl and CuBr nanocrystals in potassium-aluminaborate glass is studied. The size effect of the band edge absorption and luminescence energy is confirmed. The simultaneous presence of copper halide nanocrystals and free monovalent copper ions in the glass matrix is shown. Possible conditions for the formation of mixed CuCl-CuBr crystals are considered.

Mixed crystal formation of two gold isocyanide complexes with various ratios for continuous tuning of photophysical properties.

Mixed crystals composed of two distinct gold isocyanide complexes are reported. Characterization of the mixed crystal formation and mixing ratios are performed by single-crystal X-ray diffraction and nuclear magnetic resonance spectroscopy analyses. By changing the mixing ratio, we achieve continuous changes in the emission lifetimes and the emission quantum yields.

The Problem of Formation of Mixed Crystals and High-Efficiency K2(Co, Ni)(SO4)2 • 6H2O Optical Filters

This review, for the first time, summarizes the results of studies of the defect formation mechanisms in mixed crystals grown from aqueous solutions. The general mechanism of interaction of a crystal with a foreign solution is described (reaction of isomorphous replacement). As a result of this reaction, the crystal surface turns into a mosaic of local areas where multidirectional processes (dissolution and growth) occur simultaneously. Data on mosaic microinhomogeneity, which is a new type of composition inhomogeneity inherent solely to multicomponent crystals, is presented. A new mechanism for the mismatch stress relaxation in heterocompositions of brittle crystals grown from low-temperature solutions is described; in this case, the formation of misfit dislocations is impossible and stress relaxation occurs due to the formation of numerous inclusions at the interface. The general concept of growing high-quality mixed crystals from solutions is described, using the example of K2(Co, Ni)(SO)2 · 6H2O (KCNSH) mixed crystals.

Physicochemical Properties and Photochemical Reactions in Organic Crystals

Background:Molecular organic photochemistry is concerned with the description of physical and chemical processes generated upon the absorption of photons by organic molecules. Recently, it has become an important part of many areas of science: chemistry, biology, biochemistry, medicine, biophysics, material science, analytical chemistry, among others. Many synthetic chemists are using photochemical reactions in crystals to generate different types of organic compounds since this methodology represents a green chemistry approach.Objective & Method:Chemical reactions in crystals are quite different from reactions in solution. The range of organic solid state reactions and the degree of control which could be achieved under these conditions are quite wider and subtle. Therefore, for a large number of molecular crystals, the photochemical outcome is not the expected product based on topochemical principles. To explain these experimental results, several physicochemical factors in crystal structure have been proposed such as defects, reaction cavity, dynamic preformation or photoinduced lattice instability and steric compression control. In addition, several crystal engineering strategies have been developed to bring molecules into adequate orientations with reactive groups in good proximity to synthesize complex molecules that in many cases are not available by conventional methods. Some strategies involve structural modifications like intramolecular substitution with different functional groups to modify intermolecular interactions. Other strategies involve chemical techniques such as mixed crystal formation, charge transfer complexes, ionic and organometallic interactions. Furthermore, some examples of the single crystal to single crystal transformations have also been developed showing an elegant method to achieve regio and stereoselectivity in a photochemical reaction.Conclusion:The several examples given in this review paper have shown the wide scope of photochemical reactions in organic molecular crystals. There are several advantages of carrying photochemical reaction in the solid state. Production of materials unobtainable by the traditional solution phase reactions, improved specificity, reduction of impurities, and enhancement in the yields by the reduction of side reactions. These advantages and the multidisciplinary nature of solid-state photochemistry make this discipline quite likely to develop a lot in the future.

Melamine promotes calcium crystal formation in three-dimensional microfluidic device

Melamine, which induces proximal tubular (PT) cell damage has a greater nephrotoxic effect when combined with cyanuric and uric acids; however, it is unknown whether such effect can stimulate calcium phosphate (CaP)/calcium oxalate (CaOx) stone formation. Here, we show that melamine acts as an inducer of CaP, CaOx and CaP + CaOx (mixed) crystal formations in a time and concentration-dependent manner by stabilizing those crystals and further co-aggregating with melamine. To explore the physiological relevance of such melamine-augmented calcium crystal formation, we used 2-dimensional (2D) and 3D microfluidic (MF) device, embedded with PT cells, which also resembled the effect of melamine-stimulated CaP, CaOx and mixed crystal formation. Significantly, addition of preformed CaP and/or CaOx crystal in the presence of melamine, further potentiated those crystal formations in 3D MFs, which helped the growth and aggregation of mixed crystals. Our data show that the mechanism of such predisposition of stone formation could be largely due to co-crystallization between melamine and CaP/CaOx and pronounced effect on induction of stone-forming pathway activation in 3D MF. Taken together, melamine-induced CaP and/or CaOx crystal formation ex-vivo will help us in understanding the larger role of melamine as an environmental toxicant in producing the pathology in similar cellular microenvironments.

Tuning of the exchange interaction and the Curie temperature by mixed crystal formation of the bridging anionic ligands.

Mixed crystals with the composition [Co(NCS)x(NCSe)2-x(pyridine)2]n were prepared from solution and by annealing of Co(NCS)x(NCSe)2-x(pyridine)4. With increasing selenocyanate content, an increase of the magnetic exchange constant and of the critical temperature (Curie temperature) is observed, which offers a rational route to control these parameters in detail, without changing the metal cations.

Tuning of the Critical Temperature in Magnetic 2D Coordination Polymers by Mixed Crystal Formation

Reaction of Co(NCS)2 and Ni(NCS)2 with 4-acetylpyridine under different conditions leads to the formation of mixed crystals of the layered compound with the composition [CoxNi1–x(NCS)2(4-acetylpyridine)2]n (x = 0.15 0.3, 0.5, and 0.7). Mixed crystal formation was investigated by a combination of X-ray powder diffraction (XRPD), atomic absorption spectroscopy (AAS), simultaneous scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), differential scanning calorimetry (DSC), and magnetic and heat capacity measurements. Dependent on the synthetic method, homo- or heterogeneous mixed crystals were obtained as already indicated by XRPD, where significant differences to the pattern of physical mixtures of the homometallic counterparts [M(NCS)2(4-acetylpyridine)2]n with M = Co or Ni) with the same Co/Ni ratio are observed. Mixed crystals can also be obtained from physical mixtures under thermodynamic control, indicating that they are more stable than the homometallic compounds. This is...

Visible-light induced photocatalytic activity of electrospun-TiO2 in arsenic(III) oxidation.

In practical implementation of TiO2 semiconductors, utilization of their outstanding properties is mainly hindered by poor material quality and high operational costs. In this contribution, the electrospinning method was employed to fabricate N-doped mixed-crystalline TiO2 with exposed high-energy facets. The Ti oxide transformation process was thoroughly studied. During the mixed crystal structure formation process, the high-energy facets could be preserved due to the lower calcination temperature and the protective role of polyvinylpyrrolidone (PVP) in the electrospinning process. In addition, after calcination, the N doping, generated by the decomposition of PVP, extended the absorption spectrum of TiO2 to the visible region. These TiO2 fibers exhibited superior photooxidation of arsenite (III) to arsenate (V)in both the UV and visible light regions, mainly attributed to the exposure of high-energy facets, robust separation of photoexcited charge carriers between the anatase/rutile phases, and narrow band gap induced by the in situ N doping. Combining both robustness and scalability, the TiO2 fibers produced via this electrospinning process have the potential for a broad range of applications.

Crystal structure and spin state of mixed-crystals of iron with NCS and NCBH3 for the assembled complexes bridged by 1,3-bis(4-pyridyl)propanes

New mixed crystals, Fe(NCS) x (NCBH3)(2−x)(bpp)2, (bpp = 1,3–bis(4–pyridyl)propane) were synthesized. The formation of mixed crystals was confirmed by powder X-ray diffraction patterns and single crystal X-ray structural analysis. Elemental analyses showed that all Fe(NCS) x (NCBH3)(2−x)(bpp)2 samples had more Fe(NCS)2 unit than the preparation fraction. 57Fe Mossbauer spectroscopy revealed that all the spectra consist of only Fe(NCS)2 unit and Fe(NCBH3)2 unit. And the fraction of low-spin state in the Fe(NCBH3)2 unit changed with the change of x. The results suggested that the high spin site of Fe(NCS)2 unit affects the spin state of Fe(NCBH3)2 unit.

Growth and characterization of NixZn1−xSO4·7H2O single crystals

NiSO4·7H2O (morenosite) and ZnSO4·7H2O (goslarite) are hydrogen bonded crystals having wide applications in various fields. In an attempt to understand the formation and properties of mixed crystals based on NiSO4·7H2O and ZnSO4·7H2O, we have grown by the free evaporation method at room temperature and characterized NixZn1−xSO4·7H2O single crystals (with x having the values 0.0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1.0). The grown crystals were characterized chemically and structurally by carrying out density, X-ray powder diffraction, and atomic absorption and Fourier transform infrared spectral measurements. The grown crystals exhibit good optical transparency in the wavelength range 210–1100nm. The second harmonic generation measurements indicate a maximum efficiency for the mixed crystal with x=0.5. Results of microhardness measurements follow the normal indentation size effect. Electrical (AC and DC) measurements indicate that the grown crystals exhibit a normal dielectric behavior and the electrical conduction is understood to be due to the protonic movement. The present study indicates that the mixed crystals with x=0.2 and 0.5 are not only promising nonlinear optical materials but also useful as low dielectric constant materials.

Interplay between crystallization and glass transition in binary Lennard-Jones mixtures

In this work we explore the interplay between crystallization and glass transition in different binary mixtures by changing their inter-species interaction length and also the composition. We find that only those systems which form bcc crystal in the equimolar mixture and whose global structure for larger x(A) (x(A) = 0.6, where x(A) is the mole fraction of the bigger particles) is a mixed fcc + bcc phase, do not crystallize at this higher composition. However, the systems whose equimolar structure is a variant of fcc (NaCl type crystal) and whose global structure at larger x(A) is a mixed NaCl + fcc phase, crystallize easily to this mixed structure. We find that the stability against crystallization of this "bcc zone" is due to the frustration between the locally preferred structure (LPS) and the mixed bcc + fcc crystal. Our study suggests that when the global structure is a mixed crystal where a single species contributes to both the crystal forms and where the two crystal forms have large difference in some order parameter related to that species then this induces frustration between the LPS and the global structure. This frustration makes the systems good glass former. When x(A) is further increased (0.70 ≤ x(A) < 0.90) the systems show a tendency towards mixed fcc crystal formation. However, the "bcc zone" even for this higher composition is found to be sitting at the bottom of a V shaped phase diagram formed by two different variants of the fcc crystal structure, leading to its stability against crystallization.

Solubility measurements of (methane + ethane + propane) mixtures in the aqueous phase with gas hydrates under vapour unsaturated conditions

The equilibrium concentrations of two ternary mixtures of methane, ethane and propane in the aqueous phase with gas hydrates were measured at pressures from 6MPa to 20MPa and temperatures from 274K to 299K at different salinity levels. These conditions for the gas mixtures selected were well inside the hydrate formation envelope so that the vapour phase could not coexist in equilibrium. A laboratory procedure was developed for the formation of homogeneous mixed hydrate crystals in the absence of a vapour phase. The compositional results generated in this work were compared against experimental data reported in the literature as well as against the predictions of the CSMGem thermodynamic model (Sloan and Koh, 2008; Ballard, 2002) [1,2].

Thermal and FTIR spectral studies of various proportions of zinc magnesium ammonium sulfate

Mixed crystals of various proportions of zinc magnesium ammonium sulfate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized through thermal (TG–DTA) and FTIR spectral analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. DTA curve shows exothermic peaks in this temperature range supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulfate mixed crystals. Detailed structural analysis of the compound is under progress.

Growth and characterization of 0.1 and 0.25 zinc magnesium ammonium sulphate

Mixed crystals of 0.1 and 0.25 zinc magnesium ammonium sulphate were grown by slow evaporation of aqueous solution at room temperature. The bright and transparent crystals obtained were characterized by thermal (TG–DTA), FTIR and XRD analyses. A fitting decomposition pattern for the compound was formulated on the TG curve which shows two stage mass losses between 133 and 478.75 °C. In this temperature range, DTA curve shows exothermic peaks supporting the formulated decomposition pattern. The FTIR spectra show the vibration frequencies due to the formation of zinc magnesium ammonium sulphate mixed crystals. Detailed structural analysis of the compound is under progress.

The influence of sodium lauryl sulfate on the crystal phases of titania by hydrothermal method

In this paper, we prepared TiO2 nanostructures by a hydrothermal method and investigated the influence of the \(\mathrm{SO}_{4}^{2-}\) ion and the effect of long alkyl chains of sodium dodecyl sulfate on the crystal phases of TiO2 by experiments and theoretical calculations. The results indicate that the absorption of the H+HSO4 fragment on rutile (110) is more stable than that of the 2H+SO4 fragment and more favorable to the formation of anatase. The absorption and steric effects of sodium dodecyl sulfate on the surfaces of TiO2 grains also have an important influence on the formation of mixed crystals by changing the speed and the way of octahedral TiO6 units combining. Based on the above facts, we revised the original reaction scheme for crystalline titania formation by previous authors.

Pb-doped KCl: from adsorption to habit and crystal structure modification

Many papers dealing with alkali-halides crystal morphology have been published since the Sixties. The relationship between crystal growth or dissolution morphology and the presence of surface specific impurities is commonly recognized. Authors usually attributed morphological changes to the random adsorption of the impurity on specific crystal surfaces. The results of our research clearly show that several morphological changes can be correctly interpreted in terms of 2D-epitaxially absorbed phases [1], [2] leading both to morphological and structural changes. In the case of potassium chloride crystals, both in-situ and ex-situ observations on growing and etched crystals were performed [3] in order to demonstrate that the appearance of the octahedron in the crystal morphology is due to the step bunching effect ascribable to the precipitation of PbCl2 crystallites along the n steps on the {100} forms. Inspired by the Lian et al. [3] detailed “morphodrome” showing the crystal habit and surface modifications of KCl crystals grown in the presence of Pb as specific impurity, we performed a new series of growth and dissolution experiments in order to improve the old data. The impurity concentration ranges from 5 to 10000 ppm at constant crystallization temperature. Moreover we tried to enlarge the impurity concentration range, joining the molar ratio of the two known perovskite structures (KCl:PbCl2 and KCl:2PbCl2) in order to evaluate the continuity between morphological and structural changes from the cell distortion (anomalous mixed crystal formation due to impurity adsorption and 2D epitaxy between KCl and PbCl2) to the symmetry breakdown (from the anomalous mixed crystal at higher symmetry to the perovskite structure at lower symmetry).