Study on the morphology, crystalline structure and thermal properties of yellow ginger starch acetates with different degrees of substitution

Yellow ginger starch acetates with different degrees of substitution (DS) were prepared by reacting native starch with glacial acetic acid/acetic anhydride using sulfuric acid as catalyst. X-ray diffraction (XRD) of acetylated starch revealed that the crystal structure of native starch was disappeared and new crystalline regions were formed. Their formation was confirmed by the presence of the carbonyl signal around 1750 cm⁻¹, as well as the reduced hydroxyl groups, in the Fourier transform infrared spectroscopy (FT-IR). The scanning electron microscopy (SEM) suggested most of the starch granules disintegrated with many visible fragments along with the increasing DS. The thermal behavior of the native starch and starch acetate were investigated using thermogravimetric analysis (TGA) and differential thermal analysis (DTA), it was observed that the thermal stability of acetylated starch depends on the degree of substitution. Thermal stability of high DS acetylated starch is much better than that of the original starch when DS reached to 2.67.     

Synthesis and Structure of a Hybrid Metal Phthalate Compound and Its Magnetic Property

The hybrid transition metal – alkali metal compound, [Ni(H₂O)₆·(μ‐H₂O)₂·K₂(phth)₄(H₂O)], (phth = phthalate) ( 1 ), was synthesized from nickel(II) nitrate, KOH and potassium hydrogen phthalate, and was isolated by crystallization. Single‐crystal X‐ray analysis revealed that 1 belongs to the monoclinic system, space group P2₁/c with a = 10.455(2) Å, b = 6.8670(14) Å, c = 29.704(6) Å, γ = 98.14(3)°, R₁ = 0.0585, wR₂ = 0.1503. In the title compound, [K₂(phth)₄]²⁺ units are bonded to water‐bridged Ni chains forming 2D lamellar‐like compounds.     

Thermal degradation of star-shaped poly(?-caprolactone)

Thermal degradation of a serials of star-shaped poly(?-caprolactone) (PCL) with well-defined arm numbers and arm length was investigated. The weight loss of star-shaped PCL during heating process showed a two-stage character, and its dependence on molecular weight and multi-armed structure was well discussed. It was found that the thermal stability could be improved not only by increasing molecular weight but also by increasing arm numbers when the molecular weight is in a certain range. Based on the analyses of pyrolytic products by ¹H NMR and TGA-FTIR, two mechanisms of thermal degradation for the random cleavage of ester bonds of PCL chains were proposed. Ester bonds were pyrolyzed into alkene and carboxyl functional groups in mechanism I while they were pyrolyzed into ketene and hydroxyl functional groups in mechanism II. The effects of multi-armed structure of star-shaped PCL on the cleavage of ester bonds of PCL chains were discussed in terms of the limitation of central “core” on mobility of each PCL arm. Combined the results of viscosity analysis with thermal analysis, it could be concluded that both thermal stability and processability of PCL materials can be improved by controlling the multi-armed structures.     

N2O in small para‐hydrogen clusters: Structures and energetics

We present the minimum‐energy structures and energetics of clusters of the linear N₂O molecule with small numbers of para‐hydrogen molecules with pairwise additive potentials. Interaction energies of (p‐H₂)–N₂O and (p‐H₂)–(p‐H₂) complexes were calculated by averaging the corresponding full‐dimensional potentials over the H₂ angular coordinates. The averaged (p‐H₂)–N₂O potential has three minima corresponding to the T‐shaped and the linear (p‐H₂)–ONN and (p‐H₂)–NNO structures. Optimization of the minimum‐energy structures was performed using a Genetic Algorithm. It was found that p‐H₂ molecules fill three solvation rings around the N₂O axis, each of them containing up to five p‐H₂ molecules, followed by accumulation of two p‐H₂ molecules at the oxygen and nitrogen ends. The first solvation shell is completed at N = 17. The calculated chemical potential oscillates with cluster size up to the completed first solvation shell. These results are consistent with the available experimental measurements. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

含吡啶环的芳香醚-噁二唑类化合物的合成及其光谱研究

为开发新的高强度的有机电致发光材料, 用含烷氧基的取代苯甲酸(2)与2,6-吡啶二甲酰肼(3)在POCl3作用下, “一锅煮”法合成6个结构对称的含吡啶环的芳香醚-噁二唑4a～4f. 通过MS, IR, 1H NMR, 元素分析等手段对其结构进行了表征. 化合物的荧光性能测定结果显示此类化合物具有良好的荧光性, 其荧光发射波长均在347～507 nm范围内, 最大荧光发射波长在384 nm附近处, 且荧光强度较强. 在芳环上引入5-Br基团(4e, 4f), 化合物的荧光发射波长发生红移, 荧光强度有所减弱. 以硫酸奎宁作参比, 测定6个目标产物的荧光量子产率, 5-Br基团的引入对荧光量子产率没有明显影响. 同时讨论了代表性产物4a在不同溶剂中最大荧光激发波长处的荧光量子产率, 发现溶剂极性对该类化合物的荧光量子产率基本没有影响.     

Synthesis of highly fluorescent LaF3:Ln/LaF3 core/shell nanocrystals by a surfactant-free aqueous solution route

A surfactant-free aqueous solution route has been established for the synthesis of LaF₃:Ln³⁺/LaF₃ core/shell nanocrystals (Ln=Ce, Tb, Nd) heated at 75 °C at ambient pressure. All the as-prepared nanocrystals with spherical shape have an average size around 20 nm, and consist of well crystallized hexagonal phases. The X-ray photoelectron spectra was used to confirm that the LaF₃ shells have coated the LaF₃:Ce³⁺, Tb³⁺ cores. Compared with that of the original cores under the same conditions, the emission intensity of the LaF₃:Ce³⁺, Tb³⁺/LaF₃ and LaF₃:Nd³⁺/LaF₃ core/shell nanocrystals increased significantly of 120% and 60%, respectively. The quantum yield of the LaF₃:Ce³⁺, Tb³⁺/LaF₃ core/shell nanocrystals reached about 27% in aqueous solution. These results indicate that a significant reduction of the quenching from the surface of the core nanocrystals can be obtained by the synthesis of the core/shell structures, and this method can provide more desirable lanthanide-doped nanocrystals for potential biological applications.     

Electrophoretic separation with 2-mm inner diameter fused-silica microcolumn packed with quartz microncrystals and its application

The feasibility of a microcolumn electrophoresis technique was investigated with a 100 mm length, 2 mm I.D. fused-silica microcolumn packed with uniform quartz microncrystals prepared by hydrothermal synthesis. To evaluate the separation technique, tryptophan, phenylalanine and tyrosine were primarily separated by the microcolumn electrophoresis and detected at 216 nm without derivatization by an ordinary spectrophotometer. The separation conditions of the amino acids were optimized. With 1.5 mmol/L disodium phosphate buffer solution (pH 11.5) containing 25% (v/v) methanol and 10% (v/v) acetonitrile, the three amino acids were separated and the separation efficiency of tryptophan was 4.5 × 10⁴ plates/m. The limits of detection were 0.035, 0.22 and 0.20 μmol/L, respectively. The sample capacity of the electrophoretic microcolumn achieved 35 μL. The proposed method was used to determine these amino acids in compound amino acid injection samples without derivatization. For the simplicity and portability of the microcolumn electrophoresis, it is studied as one of the high-performance separation techniques for an in situ and real-time electrokinetic flow analysis system. For its high detection sensitivity and large sample capacity, it can be developed for preparative electrophoresis.     

Application of ortho-chloro-β-aroylthioamides in synthesis(II): an efficient one-pot, three-component synthesis of tricyclic thiochromeno[2,3-b]pyridine derivatives

Tricyclic thiochromeno[2,3-b]pyridine derivatives have been successfully synthesized in an unusual one-pot multicomponent cascade reaction from ortho-halo-β-aroylthioamides, Meldrum's acid, and aromatic aldehydes. The reaction presumably proceeds via Knoevenagel condensation-Michael addition-cyclocondensation-decarboxylation-rearrangement-intramolecular S_NAr reaction sequence. High bond forming efficiency of this reaction makes it attractive for the synthesis of thiochromeno[2,3-b]pyridine derivatives in a single step operation.     

Simultaneous Quantification of Seven Main Triterpenoid Saponins in Radix et Rhizoma Clematidis by LC–ELSD

Chinese clematis is a Chinese medicine with anti-inflammatory and anti-rheumatoid properties. Studies showed the triterpenoid saponins of this herb represent the major active components with therapeutic activities for the treatment of inflammatory diseases. The LC–ELSD method was developed to quantitatively analyze seven major triterpenoid saponins in 22 samples from different habitats. The linearity, sensitivity, precision, and accuracy were investigated. It showed the great variation of the contents of each saponin. We concluded clematichinenoside AR is the major saponin in all the samples. This method can be used to effectively evaluate and monitor the quality of Chinese clematis in clinical use.     

Development and validation of an immunochromatographic assay for rapid multi-residues detection of cephems in milk

A one-step immunochromatographic assay (ICA) was developed for the detection of seven kinds of cephems in milk. Polyclonal antibodies (PcAb) with group-specific to cephems were raised in rabbits after immunization with cephalexin-keyhole limpet hemocyanin (KLH) conjugate. The specificity of anti-sera was determined by indirect competitive enzyme-linked immunosorbent assay (icELISA), and the 50% inhibitions (IC₅₀) of cephalexin and cefadroxil were obtained at 1.5 ng mL⁻¹; IC₅₀ of cefatiofur, cefapirin, cefazolin, cefalothin and cefotaxine were 4, 3.7, 3.2, 4.5 and 5 ng mL⁻¹, respectively. The PcAb against cephems were conjugated to colloidal gold particles as the detection reagent for ICA strips to test for cephems. This method achieved semi-quantitative detection of cephems in <5 min, with high sensitivity to cephalexin and cefadroxil (both 0.5 ng mL⁻¹). At the same time, cefatiofur, cefapirin, cefazolin, cefalothin and cefotaxine were detected at <100 ng mL⁻¹ in spiked processed-milk samples. This method was compared with an enzyme-linked immunosorbent assay by testing 40 milk samples, and the positive samples were validated by a high-performance liquid chromatographic method, with an agreement rate of 100% for both comparisons. In conclusion, the method was rapid and accurate for the multi-residue detection of cephems in milk.