Fluorescence microscopy observation of self-organized microstructure formed by a rare earth compound

The morphologies of monolayers containing Eu(TTA)3Phen (TTA=thenoyltrifluoroace-tone, Phen = 1, 10-phenanthroline) were studied at the air/liquid interface on different subphases by fluorescence microscopy (FM). The composite subphase was the basic premise for the stable existence of the rare earth compound at air/liquid interface. The process that rare earth compound phase changes from liquid expanded state to liquid condensed state corresponded to a plateau in the π-A isotherm. In the pure Eu(TTA)3Phen monolayer, rod domains of Eu(TTA)3Phen formed and packed with no order. In the mixed monolayers with stearic acid (SA), phase transition of SA occurred first and formed domains with an electric gradient field, which induced the rare earth compound to form luminescent ring domains. Influence of intermolecular interaction on the self-organized microstructure was revealed.     

Synthesis and Soft Magnetic Properties of Mg-doped Ni Nanoparticles

Mg-doped Ni nanoparticles with good soft magnetic properties were prepared with the sol-gel method and were sintered at 400, 500, 600, and 900℃ in argon atmosphere, respectively. The structure and magnetic properties of the samples were studied by means of X-ray diffraction, TEM, and VSM magnetometers. X-Ray powder diffraction results show that Ni-Mg solid solution was formed with the single phase of face-centered cubic（fcc） structure. The particle size became larger with the increase of temperature. When the sintering temperature was 400 °C, the particle size was 6.3 nm, whereas it was 46.2 nm at 900 °C. Both the saturation magnetization（Ms） and the coercivity were enhanced with the increase of the particle size. The Ms values of the samples ranged from 18.965 to 46.766 emu/g and the coercivity ranged from 1051.3568 to 9145.0848 A/m.     

Liquid crystal character controlled by complementary discotic molecules mixtures: Columnar stacking type and mesophase temperature range

In this work, the mesophase properties were tuned via mixing two discotic molecules with structural complementarity. Compared with the liquid crystalline hexakis(n-hexyloxy)triphenylene(H6TP)materials(columnar hexagonal phase from 53 8C to 91 8C), mesophase types as well as phase transition temperatures varied with the introduction of crystalline hexaazatriphenylene derivative(PBH)molecules. The introduction of less than 33% amount of PBH disrupted the columnar hexagonal phase formed by H6 TP remarkably, followed by the decreased clearing temperatures of liquid crystals. As the PBH amount was further increased, the destroyed columnar hexagonal phase was turned into the columnar rectangular phase, in which H6 TP and PBH molecules together formed the columnar mesophase. The formation of new mesophase contributed to the enlarged mesophase temperature(from44 8C to 144 8C). We speculated that the alkyl chains interaction induced by the PBH component competed with the strong p–p stacking between H6 TP molecules, thus altering the liquid crystalline properties including mesophase types and phase transition temperatures.     

Solubilities, Densities and Refractive Indices of Rubidium Chloride or Cesium Chloride in Ethanol Aqueous Solutions at Different Temperatures

The data of solubilities, densities and refractive indices of rubidium chloride or cesium chloride in the system CEHsOH-H2O were measured by using a simple accurate analytical method at different temperatures, with mass fractions of ethanol in the range of 0 to 1.0. In all cases, the presence of ethanol significantly reduced the solubility of rubidium chloride and cesium chloride in aqueous solution. The solubilities of the saturated solutions were fitted via polynomial equations as a function of the mass fraction of ethanol. The CsC1-C2H5OH-H2O ternary system appeared in two liquid phases： alcoholic phase and water phase, when the mass fractions of ethanol were in the range of 10.37% to 49.59% at 35 ℃. Density and refractive index were also determined for the same ternary systems with varied unsaturated salt concentrations. Values for both experiment and theory were correlated with the salt concentrations and proportions of alcohol in the solutions. The equations proposed could also account for the saturated solutions.     

Deformation Temperature and Lamellar Thickness Dependency of FormⅠto Form Ⅲ Phase Transition in Syndiotactic Polypropylene during Tensile Stretching

Phase transition from form Ⅰto form Ⅲ in syndiotactic polypropylene crystallized at different conditions during tensile deformation at different temperatures was investigated by using in situ synchrotron wide angle X-ray diffraction technique. In all cases, the occurrence of this phase transition was observed. The onset strain of this transition was found to be crystalline thickness decided by crystallization temperature and drawing temperature dependent. The effect of drawing temperature on this phase transition is understood by the changes in mechanical properties with temperature. Moreover, crystalline thickness dependency of the phase transition reveals that this form I to from III phase transition occurs first in those lamellae with their normal along the stretching direction which have not experienced stress induced melting and recrystallization.     

Deformation temperature and lamellar thickness dependency of Form I to Form III phase transition in syndiotactic polypropylene during tensile stretching

Phase transition from form Ⅰ to form Ⅲ in syndiotactic polypropylene crystallized at different conditions during tensile deformation at different temperatures was investigated by using in situ synchrotron wide angle X-ray diffraction technique. In all cases, the occurrence of this phase transition was observed. The onset strain of this transition was found to be crystalline thickness decided by crystallization temperature and drawing temperature dependent. The effect of drawing temperature on this phase transition is understood by the changes in mechanical properties with temperature. Moreover, crystalline thickness dependency of the phase transition reveals that this form Ⅰ to from Ⅲ phase transition occurs first in those lamellae with their normal along the stretching direction which have not experienced stress induced melting and recrystallization.     

纳米粒子相变的分子动力学研究：Cu453的性质、结构与结晶成核

Molecular dynamics （MD） computer simulations have been carried out to study the structures, properties and crystal nucleation of nanoparticles with 453 Cu atoms. Structure information was analyzed from the MD simulations, while properties of nanoparticles of Cu453, such as melting point, freezing temperature, heat capacity and mo- lar volumes, have been estimated. The face center cubic （FCC） phase and icosahedron （Ih） phase were observed during the quenching process, and nucleation rates of crystallization to FCC crystal of Cu453 at temperatures of 650, 700, 750, and 800 K were analyzed. Both classical nucleation theory （CNT） and diffuse interface theory （DIT） were used to interpret our observed nucleation rates. The free energy and diffuse interface thickness between the liquid and the FCC crystal phases were estimated by the CNT and DIT respectively, and the results show that the DIT does not work properly to the system.     

FOURIER TRANSFORM INFRARED STUDY OF FRACTIONATED AROMATIC POLYESTERS

Infrared spectra at different temperatures have been studied for fractions ofa liquid crystal tormmg aromatic polyester. The molecular interactions in different phases and their changes duringthe transitions were discussed. Abrupt frequency shift was found for bands of groups both in mesogens and flexible spacers during fusion and isotropization transitions. It may imply that both the mesogens and the flexible spacers are included in the same crystalline phase and give their contributions to the formation of the mesophase. The splitting into doublet of the C—O stretching vibrations was observed for both the aromatic and aliphatic esters and was attributed to the existence of local regions for ester groups different in ordering. The more ordered regions do not disappear completely even in the isotropic liquid phase.     

SYNTHESIS AND CHARACTERIZATION OF AMPHOTERIC HYDROGELS BASED ON N-CARBOXYETHYLCHITOSAN

New amphoteric hydrogels based on carboxyethylchitosans(CECH)with various degrees of substitution(DS) were prepared using different amounts of epichlorohydrin(ECH)as the crosslinking agent.The equilibrium swelling ratio (SW)was determined as functions of pH and salt concentration.The hydrogels show typical amphoteric character responding to pH change of the external medium.At isoelectric point(IEP),the hydrogels shrink.The DS value has important effect on the swelling properties of the hydrogels.When the...     

Preparation and Characterization of High-quality α-Al2O3/Al4.59Si1.41O9.7/Al2TiO5 Multiphase Material

The α-Al2O3/Al4.59Si1.41O9.7/Al2TiO5 multiphase material with high performance was prepared by reaction sintering. The influence of different formulas on the structures and properties of multiphase material was investigated to determine the optimal formula. Crystalline structure and cell parameters of sintered samples were characterized by XRD. Microstructure of all samples was observed by SEM. The properties of sintered samples were investigated. The results show that corundum phase (α-Al2O3 ), mullite solid solution phase (Al4.59Si1.41O9.7 ) and aluminium titanate phase (Al2TiO5 ) were formed in the sintered samples. Different formulas would not change the symmetry of each crystalline phase, but caused slight change in their cell parameters. The optimal formula was determined to be coarse corundum of 36%, fine corundum of 21%, total amount of three kinds of clay of 33%, and TiO2 of 12%, which possessed a comparatively ideal microstructure and optimal properties.     

Effect of L64 on the Phase Behavior of 1-Dodecyl-3-methylimidazolium Chloride/Water System

Phase behavior of ternary system involving surfactant‐like ionic liquid 1‐dodecyl‐3‐methylimidazolium chloride ([C₁₂mim]Cl), water, and nonionic surfactant PEO‐PPO‐PEO block copolymer (Pluronic L64) is investigated at 25°C. Hexagonal (H₁) and lamellar liquid crystal phase (Lα) are found in [C₁₂mim]Cl/H₂O/L64 system by using polarized optical microscopy (POM), small‐angle X‐ray scattering (SAXS) techniques and ²H NMR spectra. The phase structure (H₁ phase), which is formed in [C₁₂mim]Cl/H₂O binary system, is not changed when L64 with a low concentration is added. However, phase transitions will occur from hexagonal to multiphases of H₁ and cubic phases (C), then to Lα+C phases with constant [C₁₂mim]Cl/H₂O ratio and increasing L64 concentration. Moreover, at given L64 (5%, 20%) concentration, the lattice parameter of H₁ or Lα phase decreases with increasing [C₁₂mim]Cl/H₂O ratio. Fourier transform infrared (FTIR) spectra indicate that the H‐bonded network comprising an imidazolium ring, chloride ion and water formed in [C₁₂mim]Cl/H₂O binary system is disrupted upon addition of L64. This is helpful to the phase transition, due to the decreasing of interfacial curvature induced by dehydration of hydrated layer after the addition of PEO block of L64.     

Investigation of AOT reverse microemulsions in supercritical carbon dioxide

Bis(2-ethylhexyl) sodium sulphosuccinate (AOT) was successfully solubilised in supercritical carbon dioxide (scCO₂), with ethanol or pentanol as co-solvent. Three molecular spectroscopic probes: methyl orange (MO), 8-hydroxy-1,3,6-pyrenetrisulphonic acid trisodium salt (HPTS), and riboflavin (RF) were used to examine the solubilisation characteristics of the water/scCO₂ microemulsions formed with AOT. MO was extracted at various operating conditions, although the wavelength of its solvatochromic absorption maximum was not indicative of bulk water properties. Instead, the spectral results imply that MO may be located at the surfactant/water interface. The highly water-soluble dye HPTS was unable to be extracted into scCO₂/AOT/water systems, suggesting that the water in the reverse micelle core was not as polar under supercritical conditions as those at ambient conditions. Finally, RF was extracted into the supercritical phase (40°C, 175 bar) with pentanol co-solvent, with an apparent enhanced uptake compared with the value at 40°C and ambient pressure in bulk water. This appears to be due to the presence of microcrystals dispersed in the supercritical phase.     

Low-pH-induced transformation of bilayer membrane into bicontinuous cubic phase in dioleoylphosphatidylserine/monoolein membranes

Cubic biomembranes, nonbilayer membranes with connections in three-dimensional space that have a cubic symmetry, have been observed in various cells. Interconversion between the bilayer liquid-crystalline (L(alpha)) phase and cubic phases attracted much attention in terms of both biological and physicochemical aspects. Herein we report the pH effect on the phase and structure of dioleoylphosphatidylserine (DOPS)/monoolein (MO) membranes under a physiological ion concentration condition, which was revealed by small-angle X-ray scattering (SAXS) measurement. At neutral pH, DOPS/MO membranes containing high concentrations of DOPS were in the L(alpha) phase. First, the pH effect on the phase and structure of the multilamellar vesicles (MLVs) of the DOPS/MO membranes preformed at neutral pH was investigated by adding various low-pH buffers into the MLV suspension. For 20%-DOPS/80%-MO MLVs, at and below pH 2.9, a transition from the L(alpha) to cubic (Q(224)) phase occurred within 1 h. This phase transition was reversible; a subsequent increase in pH to a neutral one in the membrane suspension transformed the cubic phase into the original L(alpha) phase. Second, we found that a decrease in pH transformed large unilamellar vesicles of DOPS/MO membranes into the cubic phase under similar conditions. We have proposed the mechanism of the low-pH-induced phase transition and also made a quantitative analysis on the critical pH of the phase transition. This finding is the first demonstration that a change in pH can induce a reversible phase transition between the L(alpha) and cubic phases of lipid membranes within 1 h.     

Ternary phase equilibria for the sodium chloride–sodium sulfate–water system at 200 and 250 bar up to 400°C

Phase equilibria in the NaCl–Na₂SO₄–H₂O system were investigated at 200 and 250 bar for total salt concentrations ranging from 5 to 20 wt.% total salt over temperatures ranging from 320 to 400°C. In addition to providing data for this ternary system, the experiments also added information on the phase behavior of the two binary systems: NaCl–H₂O and Na₂SO₄–H₂O. For salt mixture compositions which were rich in sodium sulfate, a solid phase was observed to nucleate from the homogeneous liquid phase. Salt mixture compositions which had a high fraction of sodium chloride exhibited a vapor separation from a homogeneous liquid phase. By fitting curves to the solid–liquid and vapor–liquid separation temperatures, the temperature and composition of a constrained invariant point where liquid, solid salt and vapor are in equilibrium were estimated. These estimates were performed at discrete compositions of 5, 10, 15 and 20 wt.% total salt at pressures of 200 and 250 bar. The temperature and composition of the invariant point increased with increasing pressure following a simple thermodynamic model for boiling point elevation in a nearly ideal solution.     

蔗糖对MO/水立方液晶体系流变性质的影响

主要研究了蔗糖对甘油单油酸脂(monoolein, MO)/水立方液晶体系的流变学性质及其相行为的影响. 根据体系流变性质的变化和偏光显微镜照片, 得出随着蔗糖含量的增加, MO/水体系发生了由反相立方液晶到反相六角状液晶的相转变. 蔗糖与MO分子通过氢键相互作用, 减弱了两亲分子间的静电斥力. 当蔗糖含量增加到一临界值时, 体系的立方结构被破坏, 继续增加蔗糖的含量, 体系就会形成新的反相六角状液晶.     

Application of reversed-phase high-performance liquid chromatography for the separation of deuterium and hydrogen analogs of aromatic hydrocarbons

Substitution of hydrogen by deuterium in aromatic hydrocarbons can alter various properties significantly. Benzene, toluene, naphthalene, anthracene, phenanthrene, biphenyl and durene are separated from their deuterium analogs by reversed-phase (C₁₈ liquid chromatography with acetonitrile/water mobile phases and ultraviolet detection. Deuterium compounds always elute before the hydrogen analog; possible explanations are given. The elution pattern and retention times of anthracene and phenanthrene were unchanged when D₂O replaced H₂O as the mobile phase component.     

Phase diagrams and physicochemical properties of Li<Superscript>+</Superscript>,K<Superscript>+</Superscript>(Rb<Superscript>+</Superscript>)//borate–H<Subscript>2</Subscript>O systems at 323 K

The phase and physicochemical properties diagrams of Li⁺,K⁺(Rb⁺)//borate–H₂O systems at 323 K were constructed using the experimentally measured solubilities, densities, and refractive indices. The Schreinemakers’ wet residue method and the X-ray diffraction were used for the determination of the compositions of solid phase. Results show that these two systems belong to the hydrate I type, with no solid solution or double salt formation. The borate phases formed in our experiments are RbB₅O₆(OH)₄ · 2H₂O, Li₂B₄O₅(OH)₄ · H₂O, and K₂B₄O₅(OH)₄ · 2H₂O. Comparison between the stable phase diagrams of the studied system at 288, 323, and 348 K show that in this temperature range, the crystallization form of salts do not changed. With the increase in temperature, the crystallization field of Li₂B₄O₅(OH)₄ · H₂O salt at 348 K is obviously larger than that at 288 K. In the Li⁺,K⁺(Rb⁺)//borate–H₂O systems, the densities and refractive indices of the solutions (at equilibrium) increase along with the mass fraction of K₂B₄O₇ (Rb₂B₄O₇), and reach the maximum values at invariant point E.     

Hydrothermal synthesis and morphology variation of cadmium hydroxyapatite

Cadmium hydroxyapatite (Cd-Hap) crystals were synthesized by hydrothermal method at 200 °C using the solutions of Cd(NO₃)₂·4H₂O and (NH₄)₂HPO₄. Influences of pH values and reaction time on the crystalline phases and morphology of the products were investigated. In low pH reaction media, Cd₅H₂(PO₄)₄·4H₂O was formed and a relatively high pH reaction media was necessary to obtain Cd-Hap. Morphology of the Cd-Hap crystals changed from stubby hexagonal prismatic to rod-like in shape with the increase in the pH value. This morphological change was explained by the difference in growth mechanism through intermediate phases, Cd₅H₂(PO₄)₄·4H₂O in the low pH reaction media and Cd₂P₂O₇·5H₂O in the high pH reaction media.     

Facile synthesis of PbSe hollow nanostructure assemblies via a solid/liquid-phase chemical route and their electrogenerated chemiluminescence properties

Spherical PbSe hollow nanostructure assemblies (HNSAs) were synthesized by a simple one‐pot solid/liquid‐phase reaction in which solid KPbI₃ ? 2 H₂O and SeO₂ are heated in oleic acid/dodecylamine/1‐octadecene at 250 °C for 30 min. XRD analysis shows that the obtained product is cubic‐phase PbSe and well crystallized. FESEM and TEM images reveal that the obtained spherical PbSe assemblies are made up of small, irregular, and fused hollow nanostructure building blocks. On the basis of temperature‐ and time‐dependent investigations as well as control experiments, molten‐salt corrosion of solid PbSe nanocrystal aggregates formed in situ during the high‐temperature ripening stage is suggested to explain the formation of such novel assemblies. Moreover, when the reaction temperature is further increased to 280 or 320 °C with other conditions unchanged, cubic and orthorhombic mixed‐phase PbSe HNSAs is generated. The obtained PbSe HNSAs exhibit excellent electrogenerated chemiluminescence (ECL) performance. Two strong and stable emission peaks at about ?1.4 and +1.5 V (vs. Ag/AgCl) are observed. In particular, the ECL intensity is influenced by the crystal phase of PbSe.     

Rheology and microstructure studies of SDS/CTAB/H2O system

Phase behavior of mixed sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) aqueous solution was studied. The rheological properties and microstructure were investigated using a rheostat and freeze-fracture technique and are shown to be closely related to the phase behavior. Experimental investigations reveal two symmetrical aqueous two-phase systems (ATPS) in the ternary phase diagram of SDS/CTAB/H₂O system. In the surfactant rich phase of ATPS or in the adjacent stoichiometric state of ATPS, the system has high viscosity because of its long range ordered structure. Lamellar phase was found in the high viscosity samples in which the cationic and anionic surfactant are in 1: 3 or 3: 1 stoichiometry. In addition, the viscosity has a tendency to increase when salt was added to the solution. The viscosity increase is due to the salt can screen the repulsion between different charged headgroups and thus reduces the effective size of surfactants and facilitates the spherical or rod likes micelles to be transformed to worm-like micelles which can form hexagonal or liquid crystal phases. Large-size salt ions like sodium sulfate (especially organic salt ions) have more significant effect on the surfactant solution viscosity. The text was submitted by the authors in English.