Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboadenylic acid) and poly(ribouridylic acid)

Dissipative drying patterns of aqueous mixtures of potassium salts of poly(riboadenylic acid) (KPolyA) and poly(ribouridylic acid) (KPolyU) were studied on a cover glass, a watch glass and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and the inner area of the dried film was observed. The fine multiple ring structures formed when the affinity of the polymer with the substrate is strong. Microscopic drying patterns changed drastically depending on the location in the dried film. Microscopic drying patterns were mainly dendritic long rods and sword (halberd)-like rods. They are assigned to the crystals of double-stranded and triple-stranded helices of the A:U and A:2U complexes, respectively. Cross-like drying patterns are also observed originated from the salt-polymer interaction.     

Dissipative crystallization of aqueous mixtures of potassium salts of poly(riboguanylic acid) and poly(ribocytidylic acid)

Drying patterns of aqueous solutions of potassium salts of poly(riboguanylic acid) (KPolyG), poly(ribocytidylic acid) (KPolyC), and their mixtures KPolyG + KPolyC were studied on a cover glass, a watch glass, and a glass dish at room temperature. Accumulation of the polymers forming the broad rings near the outside edge and also in the inner area of the dried film was observed. The fine multiple ring structures formed, which supports the fact that the affinity of the polymer with the substrate is strong. Typical microscopic drying patterns of KPolyG, KPolyC, and KPolyG + KPolyC were spherulites, dendritic long rods, and sword (harberd)-like rods, respectively. The patterns changed depending on the location in the dried film. The dendritic long rods and sword-like rods were assigned to the crystals of double-stranded and/or triple-stranded helices of the G:C and 2G:C complexes. Cross-like drying patterns that originated from the salt-polymer interaction are also observed. The relationship between the polymer complexation of KPolyG + KPolyC systems and the drying patterns is similar to that of KPolyA (potassium salt of poly(adenylic acid)) + KPolyU (potassium salt of poly(uridylic acid)).     

Flame AAS determination of dopants and trace metal impurities in single crystals of potassium titanylphosphate

A flame AAS method is used for the determination of dopants and impurities in potassium titanylphosphate (KTP) single crystals. Sample digestion using sulphuric acid and hydrofluoric acid is proposed as being the most appropriate procedure. The effect of major and minor components in the sample solution on the analytical signal is studied. The content of the dopants Cr, Mn and Ni (at a level of about 1 mg g(-1)) as well as the content of the impurities Fe, Na, Mg, W and Al (from 4 mug g(-1), depending on the trace metal) in the KTP single crystals is determined. The precision of the method is characterized by a relative standard deviation of 3-10%. The accuracy is checked by comparison with ICP-AES data for the trace element content in the KTP single crystals.     

Dissipative crystallization of sodium salts of carboxymethyl cellulose

Drying dissipative patterns were observed at room temperature on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous solution of sodium salts of carboxymethyl cellulose (NaCMC) having different molecular weights in the presence of sodium chloride and in their absence. Without salt, the polymers were slightly hygroscopic and did not dry up completely on the substrates. Single crystals of the NaCMC without salt were short rodlike and quite similar to those of the other polysaccharides studied hitherto, i.e., hydroxypropyl cellulose and sodium dextran sulfate. Morphology of the polymer crystals were short rods, long dendritic rods, and/or hedrite assemblies depending on location in the dried film and in the presence of sodium chloride. Spoke-like orientation of the long dendritic rods appeared on a cover glass and a watch glass especially for NaCMC of low molecular weights.     

The growth and characterization of a metal organic crystal, potassium thiourea thiocyanide

The growth and characterization of a new non-linear organometallic crystal, potassium thiourea thiocyanide (PTT) is reported. The growth of single crystals was accomplished by the slow evaporation solution growth method. The grown crystals were characterized by XRD, TG–DTA, UV, and FTIR spectral analyses. PTT has good optical transmission in the entire visible region which is an essential requirement for a non-linear crystal. TG curve of PTT undergoes complete decomposition between 176 and 1,000 °C in three steps with corresponding three DTA peaks. The high thermal stability of organometallic crystals are due to strong bonding existing between the conjugation layers of thiourea molecule and the potassium ions.     

Surface precipitation of highly porous hydrotalcite-like film on Al from a zinc aqueous solution

A hydrotalcite-like film has been successfully deposited on an Al-bearing glass substrate based on an interface reaction between an Al layer and a zinc aqueous solution. The film selectively grew on the Al surface but not on the glass surface. The film on Al was composed of layered nanosheets of a hydrotalcite-like compound containing Al and Zn. Comparably, deposits on the plastic surface and precipitates in solution were wurzite-type ZnO with various morphologies depending upon the preparation conditions. At low supersaturation degrees, single crystals and superstructures of Zn-Al hydrotalcite were also obtained. This porous hydrotalcite film has a potential application as catalyst supports, environmental materials, or matrixes for hydrotalcite-based nanocomposite films. Using Al as a reaction interface makes it easy to coat porous hydrotalcites on a series of matrix materials varying in shapes and properties, which is important for achieving practical applications. In addition, the method developed should be widely applicable to other systems for the preparation of porous or oriented hydrotalcite-like thin films by an appropriate combination of divalent/trivalent solution-substrate systems.     

Design and testing of a small-scale sublimation apparatus

In many areas of scientific research and development, for example in the pharmaceutical industry, it is important to prepare and to characterize crystals of pure organic compounds which are thermodynamically stable. The formation of crystals from the gas phase is technically less straightforward than crystallisation from solution, but sublimation techniques can have several important features. In the present paper we report the design and testing of a novel apparatus for small scale sublimation and fractional deposition of crystals. The instrument has been developed with special reference to the needs in the pharmaceutical industry. A few mg of the samples are enclosed, under reduced pressure, in thin-walled glass tubes, along which a well defined temperature gradient can be formed. During an experiment the substance will sublime from the hot end of the glass tube and crystals will be deposited along the temperature gradient. The applicability of the instrument has been verified by experiments with several test compounds. Results from experiments with carbamazepine, are reported in some detail. Carbamazepine single crystals of high quality were obtained and the transition temperature between the triclinic (Form I) and the monoclinic (Form III) crystal modifications agreed with literature values.     

Dissipative crystallization of sodium salt of deoxyribonucleic acid

Drying patterns of aqueous solutions of sodium salt of deoxyribonucleic acid (NaDNA) were studied on a cover glass, a watch glass, and a Petri glass dish at room temperature. Orientation of the rod-like single crystals of NaDNA molecules in the radial direction was observed especially at low polymer concentrations. The ratios of the size of the broad ring against initial size of the liquid on a cover glass and a watch glass were very small between 0.05 and 0.1 compared with those of the typical polyelectrolytes. Main cause is the compact conformation of NaDNA forming single or double stranded helix structures in the dried film. Microscopic drying patterns were long rods accompanied with the many short rods especially on a cover glass. Thick and short rods and dendritic crystals were fogrmed at the inward and outward areas of the dried films, respectively, on a watch glass and a Petri glass dish. Rod-like and dendritic crystals resembled the distorted hedrite and/or spherulite structures. Dissipative crystallization such as the orientation and accumulation of the single crystals of NaDNA were observed and the importance of the convectional and sedimentation processes was demonstrated during the course of crystallization.     

不同结晶度的乙二醇及其水溶液玻璃化转变与焓松弛

为了考察晶体成分对无定形成分玻璃化转变和结构松弛行为的影响,利用差示扫描量热法(DSC),结合低温显微技术,研究了乙二醇(EG)及其50％水溶液在不同结晶度时的玻璃化转变和焓松弛行为.采用等温结晶方法控制骤冷的部分结晶玻璃体中的晶体份额.DSC结果表明,对于部分结晶的EG,只有单一的玻璃化转变过程,而对于50％EG,当结晶度不同时,不同程度地表现出两次玻璃化转变（无定形相Ⅰ和无定形相Ⅱ）.相Ⅰ的玻璃化转变温度和完全无定形态的含水EG的玻璃化转变温度相一致;相Ⅱ的玻璃化转变温度要比此温度约高6 ℃.低温显微观察结果印证了DSC实验结果.DSC等温退火的实验和KWW(Kohlrausch-Williams-Watts)衰变函数分析结果表明,EG无定形和50％EG中的两种无定形有不同的焓松弛行为.     

Growth and characterization of unidirectional (100) KDP single crystal by Sankaranarayanan-Ramasamy (SR) method

Unidirectional (100) potassium dihydrogen orthophosphate (KDP) single crystals were grown by Sankaranarayanan-Ramasamy (SR) method. The (100) oriented seed crystals were mounted at the bottom of the glass ampoules and the crystals of 20mm diameter, 30 mm height and 15 mm diameter, 65 mm height were grown by SR method. The grown crystals were characterized by high-resolution X-ray diffractometry anlaysis, UV-vis spectroscopy, dielectric and microhardness studies. The high-resolution X-ray diffractometry anlaysis indicates that the crystalline perfection is excellent without having any very low angle internal structural grain boundaries. The SR method-grown unidirectional KDP has 15% higher transmittance compared to conventional method-grown crystals. The dielectric constant was higher and the dielectric loss was less in SR method-grown crystal. The crystals grown by SR method have much higher hardness value than conventional method-grown crystals. The quality of the crystal grown by SR method is better than conventional method-grown crystal.     

Studies on the growth, optical, electrical and spectral properties of potassium pentaborate (KB5) single crystals

The bulk single crystals of nonlinear optical material potassium pentaborate (KB5) have been grown by slow evaporation solution growth technique using water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. FTIR and FT-Raman measurements enumerate the functional groups present in the compound. The factor group analysis on KB5 reveals that there are 117 vibrational optical modes. The dielectric behavior of KB5 was investigated with different frequencies and temperatures.     

Do Anionic π Molecules Aggregate in Solution? A Case Study with Multi-interactive Ligands and Network Formation

An anionic π molecule can form an aggregate when a multi-interactivity is introduced, in sharp contrast to common anionic molecules that are generally difficult to stack on each other. We found that a multi-interactive ligand, 2,5,8-tri(4′-pyridyl)-1,3,4,6,7,9-hexaazaphenalenate (TPHAP⁻) exhibited a large Stokes shift and an intramolecular charge transfer, both of which were sensitive to hydrogen-bonding media. An anionic potassium salt of TPHAP⁻ in methanol formed various aggregation states depending on the concentration examined; this was revealed by steady-state spectroscopic and fluorescence lifetime measurements. Self-assembling cadmium ions and the ligands can create several morphological crystals that are controlled by the ligand concentration, among which three new structures were determined by single-crystal analysis. The X-ray structures obtained suggest that the aggregation states of the ligand in solution can be transferred to the solid system of the porous coordination networks.     

The allomorphism of a photochromic diarylethene

The photochromic diarylethene, 1,2-bis(2-methyl-5-(2,2′-dicyanovinyl)-thien-3-yl)perfluorocyclopentene (1a), was synthesized by a novel method. Two kinds of single crystals of the compound were obtained depending on the different recrystallization conditions and their structures were determined by X-ray crystallographic analysis. Allomorphism of the photochromic diarylethene was discovered. The compound underwent a photochromic reaction both in solution and in the single crystalline phase of the anti-parallel conformer.     

Structural evolution of colloidal crystals with increasing ionic strength

We have directly observed the structural evolution of colloidal crystals as a function of increasing ionic strength using confocal scanning laser microscopy. Silica colloids were sedimented onto a glass substrate in deionized water to create large, single domain crystals. The solution ionic strength was then increased by one of three methods of controlled electrolyte addition: (1) direct injection of electrolyte solutions, (2) single step diffusion of electrolyte solutions through a dialysis membrane, and (3) multiple step diffusion of electrolyte solutions of increasing ionic strength through a dialysis membrane. During direct injection of electrolyte solutions, initially large, single domain colloidal crystals were shear melted and then evolved into polycrystalline structures at low ionic strengths and gels at higher ionic strengths. Diffusion of electrolyte solutions though dialysis membranes in a single step produced gradient-driven transport that also melted initial single domain crystals to yield polycrystalline and gel structures similar to the injection approach. Interestingly, the multistep diffusion of several electrolyte solutions through dialysis membranes facilitated retention of large, single domain crystals even as particles came into adhesive contact. This was achieved by reducing the contraction rate of the crystalline lattice to allow sufficient time for diffusion-limited configurational rearrangements to occur within the evolving structure. These mechanically robust, single domain colloidal crystals may find important applications as templates for photonic materials and sensors.     

Structural, thermal and optical characterization of a Schiff base as a new organic material for nonlinear optical crystals and films with reversible noncentrosymmetry

Macroscopic single crystals of (E)-5-(diethylamino)-2-((3,5-dinitrophenylimino)methyl)phenol (DNP) were obtained from slow cooling of chloroform or dichlorometane saturated solutions at controlled temperature. X-ray diffraction analysis showed that this compound crystallizes in a noncentrosymmetric space group (P2(1)2(1)2(1)). Thermal analysis was performed and indicated that the crystals are stable until 260 °C. Second-order nonlinear optical properties of DNP were experimentally investigated in solution through EFISH technique and in solid state through the Kurtz-Perry powder technique. Crystals of compound DNP exhibited a second-harmonic signals 39 times larger than of the technologically useful potassium dihydrogenphosphate (KDP) under excitation at infrared wavelengths. In addition, the second-order nonlinear optical properties of DNP were also studied at visible wavelengths through the photorefractive effect and applied to demonstrate dynamic holographic reconstruction.     

Drying dissipative structure of sodium salts of hyaluronic acid

Macroscopic and microscopic patterns during the course of dryness of aqueous solution in sodium salts of hyaluronic acid (NaHLA) were observed on a cover glass, a watch glass, and a Petri glass dish. Dendritic and rod-like microscopic patterns, which are similar to those of sodium salts of carboxymethyl cellulose, were observed for NaHLA especially on a cover glass and a watch glass. The microscopic patterns of NaHLA are supported to be originated from the hexose groups of polysaccharides, though the similar dendritic patterns are also observed for some of polynucleotides, sodium salts of deoxyribonucleic acid, and potassium salts of poly (riboadenylic acid), for example. Macroscopic broad ring size decreased substantially from the initial size of liquid and decreased slightly as polymer concentration decreased. These observations are consistent with existence of the rather strong interpolymer affinitive forces during the course of dryness. In the coexistence of sodium chloride, microscopic dendritic patterns grew large especially on a cover glass and a watch glass, which was so often observed for polysaccharides examined hitherto. Drying patterns are clarified to be formed by the successive and cooperative processes of evaporation, convection, sedimentation, and solidification.     

Syntheses, structure, and derivatization of potassium complexes of penta(organo)[60]fullerene-monoanion, -dianion, and -trianion into hepta- and octa(organo)fullerenes

Two-electron reduction of penta(organo)[60]fullerenes C(60)Ar(5)H (Ar = Ph and biphenyl) by potassium/mercury amalgam afforded potassium complexes of the corresponding open-shell radical dianions [K+(thf)n]2[C60Ar5(2-.)]. These compounds were characterized by UV-visible-near-IR and electron spin resonance spectroscopy in solution. Anaerobic crystallization of [K+(thf)n]2[C60(biphenyl)(5)(2-.)] that exists largely as a monomer in solution gave black crystals of its dimer [K+(thf)3]4[(biphenyl)5C60-C60(biphenyl)5(4-)], in which the two fullerene units are connected by a C-C single bond [1.577(11) A] as determined by X-ray diffraction. Three-electron reduction of C60Ar5H with metallic potassium gave a black-green trianion [K+(thf)n]3[C60Ar5(3-)]. The reaction of the trianion with an alkyl halide RBr (R = PhCH(2) and Ph(2)CH) regioselectively afforded a hepta-organofullerene C60Ar5R2H, from which a potassium complex [K+(thf)n][C60(biphenyl)5(CH2Ph)(2)(-)] and a palladium complex Pd[C60(biphenyl)5(CH2Ph)2](pi-methallyl) as well as octa-organofullerene compounds C60(biphenyl)5(CH2Ph)3H2 and Ru[C60(biphenyl)5(C2Ph)3H]Cp were synthesized. These compounds possess a dibenzo-fused corannulene pi-electron conjugated system and are luminescent.     

Atomic force microscopy investigation of the mechanism of calcite microcrystal growth under Kitano conditions

A combined atomic force microscopy (AFM)-inverted optical microscopy technique has been used to image the surface of calcite single microcrystals, with dimensions of 10-20 microm, at high resolution. The microcrystals were grown on a glass substrate using the Kitano method, a process that involves the outgassing of carbon dioxide from a saturated solution of calcium carbonate. The resulting increase in the supersaturation of the solution, with respect to calcium carbonate, induces crystallization. It is demonstrated, for the first time, that calcite microcrystals formed in this way exhibit a single spiral growth hillock on the (104) surface, as evidenced by a spiral step pattern, indicating that growth occurs at steps arising from an individual screw dislocation. The subsequent reactivity of these crystals under Kitano conditions has been followed in situ using AFM imaging.     

Mechanical relaxations in trans-1,4-polyisoprene crystals

Dynamic mechanical relaxation spectra were obtained for solution-grown crystals of trans-1,4-polyisoprene (TPI) in the α and β form. For single crystal mats three relaxations were observed. The highest temperature relaxation peak was characterized as due to the crystalline regions, whereas the intermediate peak was assigned to the primary amorphous relaxation which originates from the fold regions. The nature of the amorphous regions was elucidated by examining the effect of epoxidation on the lamellar fold surface. For an epoxidized single crystal mat, the intermediate relaxation maximum shifted to a higher temperature which corresponds to the glass transition of the almost completely epoxidized TPI. These results are discussed in terms of the fold structure of the TPI single crystals.     

PXRF, μ-XRF, vacuum μ-XRF, and EPMA analysis of Email Champlevé objects present in Belgian museums

The enamel of 20 Email Champlevé objects dating between the 12th and 19th centuries was investigated by means of microscopic and portable X-ray fluorescence analysis (μ-XRF and PXRF). Seven of these objects were microsampled and the fragments were analyzed with electron probe microanalysis (EPMA) and vacuum μ-XRF to obtain quantitative data about the composition of the glass used to produce these enameled objects. As a result of the evolution of the raw materials employed to produce the base glass, three different compositional groups could be discriminated. The first group consisted of soda-lime-silica glass with a sodium source of mineral origin (with low K content) that was opacified by addition of calcium antimonate crystals. This type of glass was only used in objects made in the 12th century. Email Champlevé objects from the beginning of the 13th century onward were enameled with soda-lime-silica glass with a sodium source of vegetal origin. This type of glass, which has a higher potassium content, was opacified with SnO2 crystals. The glass used for 19th century Email Champlevé artifacts was produced with synthetic and purified components resulting in a different chemical composition compared to the other groups. Although the four analytical techniques employed in this study have their own specific characteristics, they were all found to be suitable for classifying the objects into the different chronological categories.