Influence of essential and non‐essential amino acids on calcium oxalate crystallization

The investigation on the mechanism of nucleation and growth of crystals at organic‐inorganic interfaces is crucial for understanding biological and physiological calcification processes such as the formation of urinary stones. The effects of five different amino acids on the crystallization of calcium oxalate have been investigated at pH 4.5 and 37 °C in aqueous solutions in the batch type crystallizer. The products were characterized by Scanning Electron Microscopy (SEM), Fourier Transfer Infrared Spectroscopy (FT/IR) and X‐Ray diffraction (XRD) analysis. Crystal size distribution (CSD) and filtration rate measurements were done. In order to determine the adsorption characteristics of amino acids on the calcium oxalate crystal surfaces, zeta potential measurements were also done and discussed. The results indicate that in the presence of all investigated amino acids, calcium oxalate monohydrate (COM) crystals were preferentially produced, but the crystal morphology varied with amino acid types and concentrations. Various crystal morphologies such as elongated hexagonal, coffin or platy habits were observed. In the presence of all investigated amino acids, the calcium oxalate crystallized in a monohydrate form. Electrostatic/ionic interaction, different adsorption properties and special functional effects of amino acids led to find different crystal morphology. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of citric acid and starch as emulsifier on phase formation and crystallite size of lanthanum oxide nanoparticles

Lanthanum oxide nanoparticles were synthesized via thermal decomposition method of the lanthanum nitrate in the presence of citric acid or starch as emulsifier. The effects of emulsifier and calcination temperature were investigated on the phase transformation and particle size distribution of the products. La₂O₃ nanoparticles were synthesized by drying lanthanum precursor and emulsifier solution, followed by calcination process at 600 and 900°C, respectively. Products were characterized by Fourier Transform Infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), thermal analysis (TG/DTA) and nitrogen adsorption method (porous characteristics). The morphology of the samples analyzed using scanning electron microscopy (SEM). Average crystallite size of the products was calculated by XRD data and average particle size was measured from the TEM micrographs. Lanthanum dioxycarbonate in different forms of the tetragonal and monoclinic is crystallized in the presence of citric acid and starch during the calcination at 600°C, respectively. The hexagonal structure, however, is detected as the only crystalline phase formed by calcination at 900°C.     

Structural,thermal and optical characterizations of a NLO material: L‐alaninium oxalate

An organic electro‐optic and nonlinear optical (NLO) material, L‐alaninium oxalate, was synthesized by the standard method. The synthesized material was purified by repeated recrystallization. Single crystals were grown by the slow evaporation technique. The grown crystals were transparent and had optimum dimensions (20 × 3 × 2 mm³) and were characterized by single crystal XRD, FT‐NMR, FT‐IR, TGA‐DTA and UV‐Vis‐NIR techniques. The second harmonic generation (SHG) from the material was confirmed using Nd:YAG laser. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

FT‐IR spectroscopic and thermal studies on pure and impurity added calcium tartrate tetrahydrate crystals

Pure and impurity (strontium) added calcium tartrate tetrahydrate single crystals were grown by the gel method. The FT‐IR spectra of these crystals were recorded in the wavenumber range 400–4000 cm^–1. The thermograms of the grown crystals were recorded in the temperature range 50–900 °C. FT‐IR spectra reveals the presence of water molecules, O‐H bond, C‐O and carbonyl C=O bonds. The thermograms show that these crystals are thermally unstable and decompose into its oxide through many stages. DTA curve of the pure crystal shows three endothermic and one exothermic peaks. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of ZnO nanofibers by electrospinning

Electrospun ZnO nanofibers were obtained by calcinating PVA/Zinc Acetate composite fibers at various temperatures. Atomic Force Microscopy (AFM) revealed that the ZnO fibers have diameters in the range of 100‐200 nm. The fibers were characterized by FT‐ IR, TGA‐DTA, and XRD studies. The XRD results showed that the crystal structure and the morphology of the fibers were largely dependent on the calcination temperature (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Main regularities of crystallization of calcium oxalate in the presence of amino acids

Processes of crystallization of calcium oxalate from aqueous solutions are investigated. Main regularities of the nucleation and crystal growth of calcium oxalate during mass crystallization without admixtures and in the presence of amino acids are established. The inhibiting action of the aspartic and glutamic amino acids on the growth of calcium oxalate crystals is demonstrated. Addition of amino acids does not affect the nucleation kinetics.     

Growth of barium oxalate crystals in agar–agar gel and their characterization

Single crystals of barium oxalate have been grown by gel method using agar‐agar gel as media of growth at ambient temperature. The optimum conditions were established by varying various parameters such as concentration of gel, concentration of reactant, gel setting time etc. Prismatic platy shaped transparent crystals were obtained. The grown crystals were characterized through powder X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) studies, Thermogravimetric (TGA) and Differential thermal analysis (DTA). The compound crystallizes under monoclinic structure with lattice parameters a = 6.6562 Å, b = 8.0464 Å, c = 2.8090 Å, β= 96.832°, and V = 149.38 ų. The FT‐IR spectrum indicates OH and carbonyl group along with the presence of metal‐oxygen bond. The TGA indicates 17.75% weight loss at 550°C from which the decomposition pattern is formulated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of methylammonium tetrachlorocuprate (II) dihydrate crystals

Single crystals of methylammonium tetrachlorocuprate (II) dihydrate were obtained by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature DSC studies and FTIR and far IR spectra. While the powder XRD confirms the crystallinity of the compound, the TG and DTA studies confirm the formation of the compound in the stoichiometric ratio and the presence of two water molecules of crystallization. The low temperature DSC study indicates a thermal anomaly at ‐3°C. The ordering of CH₃NH₃ group at low temperature causes phase transitions in the compound. The IR spectra characterize the various chemical bonding and water molecules in the compound. Laser Raman spectral studies under progress would help understand the mechanism of phase transitions at low temperatures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and thermal characterization of methylammonium tetrachloro zincate (II) monohydrate crystals

Single crystals of methylammonium tetrachloro zincate (II) monohydrate were grown by slow evaporation of saturated aqueous solutions at room temperature. The grown crystals were colourless, bright and transparent. The crystals were characterized through elemental analysis, powder X‐ray diffraction, thermogravimetric (TG‐DTA) and low temperature differential scanning calorimetric (DSC) techniques. While the powder XRD pattern shows the crystallinity of the compound, the elemental analysis and the TG‐DTA confirm the stoichiometry of the compound. The low temperature DSC indicates first order structural phase transition at ‐8°C during heating cycle. The FTIR and far IR spectra of the compound show characteristic vibrational frequencies due to CH₃NH₃ and ZnCl₄^2‐ ions and other chemical bonds. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of gel grown calcium pyrophosphate tetrahydrate crystals

Formation of calcium pyrophosphate dihydrate (CPPD) crystals in soft tissues such as cartilage, meniscus and synovial tissues lead afflictions. The appearance of these crystals in the synovial fluid give rise to acute arthritis attack, which is known as pseudo‐gout. The growth of calcium pyrophosphate crystals in gel medium can mimic the growth in a body. In the present study, calcium pyrophosphate tetrahydrate (CPPT) crystals are grown by a single diffusion gel growth technique and characterized by powder XRD, FT‐IR spectroscopy, TGA, kinetic and thermodynamic studies of dehydration and dielectric studies. Monoclinic crystals structure, presence of P‐O bonds and four water molecules are confirmed from powder XRD, FT‐IR and TGA studies, respectively. The dielectric investigation suggests the reduction in dielectric constant with increase in frequency. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The effect of Si/Al ratio of ZSM‐5 zeolite on its morphology,acidity and crystal size

ZSM‐5 zeolite crystal with different Si/Al molar ratios in the range of 10‐50 was synthesized using sodium silicate, aluminum sulfate and tetrapropylammonium bromide (TPA‐Br) as the organic template. The produced samples were characterized using XRD, FT‐IR, SEM and EDX techniques. All synthesized samples were found to be ZSM‐5 zeolite as confirmed by XRD and supported by FT‐IR. SEM results showed that ZSM‐5 synthesized with different Si/Al molar ratios had different morphologies and particle sizes. It was found that the average ZSM‐5 crystal size increased as Si/Al molar ratio increased. Thermogravimetric‐difference thermal analysis (TG‐DTA) technique was also used to measure the amount of template occluded inside the crystal pore. The synthesized Na‐ZSM‐5 was transformed into its acidic form, i.e., H‐ZSM‐5 using ion exchange method with ammonium nitrate solution. The H‐ZSM‐5 acidity was determined by NH₃‐TPD. These results showed that different Si/Al molar ratios have effect on surface acidity of samples. The surface areas of the H‐ZSM‐5 were measured using BET method and the results showed that, decrease in Si/Al ratio, decreased the surface area. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of Struvite‐K crystals

Struvite‐K is the natural potassium equivalent to Struvite. Struvite‐K crystals were grown by single diffusion gel growth technique in silica hydro gel medium. Struvite‐K crystals with different morphologies having transparent to translucent diaphaneity were grown with different growth parameters. The phenomenon of Liesegang rings was also observed with some particular growth parameters. The crystals were characterized by powder XRD, FT‐IR, TGA and dielectric study. The powder XRD results of Struvite‐K confirmed the orthorhombic crystal structure. The FT‐IR spectrum proved the presence of water of hydration, metal – oxygen bond and P – O bond. The TGA, DSC and DTA were carried out simultaneously. It was found that crystals started dehydrating and decomposing from 75 °C and finally at 600 °C temperature it became 64.14% of the original weight and remained almost constant up to the end of analysis. From the thermo‐gravimetry, the numbers of the water molecules associated with the crystal were calculated and found to be 5. The kinetic and thermodynamic parameters of dehydration / decomposition process were calculated. The variation of dielectric constant with frequency of applied field was studied in the range from 400 Hz to 100 kHz, which exhibited the decreasing nature of the dielectric constant as frequency increased. The dielectric study showed that a.c. conductivity increased and consequently the a.c. resistivity decreased with the increase in frequency. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of tris allylthiourea mercuric chloride crystals

Single crystals of tris allylthiourea mercury chloride (ATMC), a semi‐organic nonlinear optical material, have been grown from a low‐temperature solution growth technique by slow cooling method. In the present work, we have grown ATMC crystal which is a new nonlinear optical material (NLO) having high optical quality and its second harmonic generation (SHG) efficiency is thrice that of Urea. The grown crystals have also been subjected to various characterization studies like X‐ray diffraction, UV‐VIS, FT‐IR and TGA‐DTA. X‐ray powder diffraction study confirmed the crystal structure of ATMC, UV‐VIS /FT‐IR spectral analysis showed the crystal has good optical transmission in the entire visible region and TGA‐DTA studies showed the thermal properties and complex degradation of ATMC crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A study of primary nucleation of calcium oxalate monohydrate: II. Effect of urinary species

Kidney stones consist of various organic and inorganic compounds. Calcium oxalate monohydrate (COM) is the main inorganic constituent of kidney stones. However, the mechanisms for the formation of calcium oxalate kidney stones are not well understood. In this regard, there are several hypotheses including nucleation, crystal growth and/or aggregation of formed COM crystals. The effect of some urinary species such as oxalate, calcium, citrate, and protein on nucleation and crystallization characteristics of COM is determined by measuring the weight of formed crystals and their size distributions under different chemical conditions, which simulate the urinary environment. Statistical experimental designs are used to determine the interaction effects among various factors. The data clearly show that oxalate and calcium promote nucleation and crystallization of COM. This is attributed to formation of a thermodynamically stable calcium oxalate monohydrate resulting from supersaturation. Citrate, however, inhibits nucleation and further crystal growth. These results are explained on the basis of the high affinity of citrate to combine with calcium to form soluble calcium citrate complexes. Thus, citrate competes with oxalate ion for binding to calcium cations. These conditions decrease the amount of free calcium ions available to form calcium oxalate crystals. In case of protein (mucin), however, the results suggest that no significant effect could be measured of mucin on nucleation and crystal growth. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of semiorganic NLO crystals of LAHClBr

Single crystals of non‐linear optical (NLO) LAHClBr were grown by slow evaporation technique from its aqueous solution. Good optical quality crystals having dimensions up to 12 × 9 × 7 mm³ were obtained. The lattice parameters and morphology for the grown crystals were determined using single crystal XRD. The crystals were characterized by FT‐Raman, optical absorption, thermal (DTA and TGA) and dielectric studies. LAHClBr was found to be thermally stable up to 124.3°C. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of Bacillus subtilis on the growth of calcium oxalate

The influence of the bacteria Bacillus subtilis (B. subtilis) on the nucleation, growth and aggregation of calcium oxalate (CaOx) crystals in aqueous solution has been studied. The crystals obtained were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X‐ray powder diffractometry. The results show that, in the presence of B. subtilis, quasi‐hexagonal calcium oxalate monohydrate (COM) crystals are obtained after 24 hours of reaction at a temperature of 30°C ± 1K. However, without the presence of the bacteria, irregular CaOx crystals were obtained which contain two crystal phases: COM and calcium oxalate dihydrate (COD). This suggests that B. subtilis may promote the crystallization of COM, the major component of urinary stone. The formation mechanism of CaOx crystals in the presence of B. subtilis is explored, indicating that the cell walls and extracellular proteins of the bacteria may act as templates to induce the nucleation, growth and aggregation of CaOx crystals. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and properties of an organometallic nonlinear optical crystal: bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II) (Zn(SCN)2(C6H7N)2)

Bis(isothiocyanato)‐bis(4‐methylpyridine)zinc(II)(Zn(SCN)₂(C₆H₇N)₂), (abbreviated as ZBNC) single crystals of optical quality have been grown from acetone solution by the slow temperature‐lowering method. Its solubilities at different temperatures in acetone were measured. The X‐ray powder diffraction (XRPD) spectroscopy of ZBNC crystal was performed at room temperature. The second harmonic generation (SHG) efficiency was determined by powder technique of Kurtz and Perry using Nd:YAG laser, which is equivalent to KDP crystal. The thermal decomposition process was characterized by thermal gravity and differential thermal analysis (TG\DTA). The specific heat of the crystal is 1440.67 J/mol·K at 325 K. The IR spectrum was recorded in the 500∼3500 cm^–1 region, using KBr pellets on a Nicolet 170sx FT‐IR spectrometer. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Inhibition of Calcium Oxalate Monohydrate Crystal Growth in High and Low Ionic Strength Solutions

The effect of additives on the kinetics of growth of calcium oxalate monohydrate crystals has been studied. Conductivity and potentiometry measurements have been compared. Growth rates were calculated from precipitate curves by a cubic spline method. An approach consisting on the calculation of rate constants and orders of reaction from logarithmic plots of growth rate versus supersaturation has been followed to study crystal growth kinetics. This method revealed that the presence of additives is causing not only a decrease on the rate constant but an increase on the order of reaction as well. The effect of additives (EDTA, citrate and phytate) was considerably weaker in high ionic strength media. Phytate produced a complete blockage of crystal growth in concentrations as low as 2 × 10^—6 mole/L in both methods.     

柠檬酸钾对尿石患者和正常人尿液凝胶中草酸钙晶体生长的影响

采用扫描电子显微镜(SEM)和X射线衍射(XRD)方法,比较研究了防石药物柠檬酸钾(K3cit)在尿石患者尿液和正常人尿液制备的凝胶中对草酸钙(CaOxa)晶体生长的影响.没有加入K3cit时,CaOxa晶体均以一水草酸钙(COM)为主要晶相,加入K3cit后,不但COM晶体变得圆钝,比表面积减小,而且诱导了二水草酸钙(COD)生成.随着K3cit浓度从0.10增加到0.20 mol/L,在正常人尿液凝胶中COD晶体的百分含量从20;增加到45;,而在CaOxa结石患者尿液凝胶中,不但COD含量从10;增加到25;,而且K3cit可诱导草酸钙成核,从而产生大量的小尺寸草酸钙晶体,这有利于阻止草酸钙晶体变大形成尿石.本结果可为临床上治疗CaOxa结石提供启示.     

不同晶相草酸钙晶体的选区电子衍射和X射线衍射比较分析

在卵磷脂-水脂质体中制备了一水草酸钙(COM)、二水草酸钙(COD)和三水草酸钙(COT).并对它们分别进行了透射电镜(TEM)、选区电子衍射分析(SAED)和X射线衍射(XRD)分析.TEM结果表明,COM、COD和COT均为泡状,粒径约80～150nm.将SAED结果与XRD结果对比分析,发现将SAED图谱指标化后所得的衍射数据与XRD的特征峰值基本相符,但在相对强度上存在差别.本实验结果表明,将TEM、SAED和XRD技术联合分析纳米级草酸钙晶体,不但可以观察纳米级草酸钙的形貌,而且能对其晶相、单晶和多晶等进行深入的了解.