Effective synthesis of novel O-acetylated compounds over ZrO2-Al2O3 solid acid

The solid acids such as ZrO₂, Al₂O₃ and ZrO₂-Al₂O₃ containing different ZrO₂ loadings (10–80 mol%) were prepared by solution combustion method (SCM) and characterized for their total surface acidity by NH₃-TPD/n-butylamine back titration method and crystallinity by powder X-ray diffraction (PXRD) technique. These solid acids were evaluated for their catalytic activity in the synthesis of novel O-acetylated products from substituted phenols, pyridine alcohols and aryl alcohols with acetic anhydride (AA) as an acetylating agent. The reaction conditions were optimized by varying the catalyst, molar ratio of the reactants, reaction temperature and amount of the catalyst. All the solid acids used in this study exhibited good catalytic activity in the reaction. In particular, ZrO₂-Al₂O₃ containing 80 mol% of ZrO₂ was found to be highly active in the acetylation reaction with high yield of acetylated products. Triangular correlation between the surface acidity, crystallinity and catalytic activity of solid acids was observed. These solid acids were found to be reactivable and reusable.     

Single precursor-based luminescent nitrogen-doped carbon dots and their application for iron (III) sensing

Iron III (Fe³⁺) sensing is of great importance for monitoring its levels in different environmental and biological systems since its levels are tightly associated with many environmental concerns and serious diseases. Compared to the ordinary Fe³⁺ detection methods involving the sophisticated and expensive instruments, the use of fluorescent materials with short response time and low cost attracts much attention. Amongst a variety of fluorescent materials, a nitrogen-doped carbon dot (N-CD) is emerging as promising luminescent materials for biosensing due to their superior photoluminescent properties, good water solubility, and biocompatibility. Herein, N-CD prepared via a green and cost-effective one-pot hydrothermal method using a new single precursor N-(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA) as both the carbon and nitrogen sources is reported. The blue fluorescent emission of N-CDs is quenched by the addition of Fe³⁺, and the quenching intensity is concentration dependent in the wide range (0.76–400 μM) with a detection limit of 0.16 μM. The quantum yield for the as prepared N-CDs is 14.17%. The N-CDs also show a high selectivity for Fe³⁺ chelation amongst a range of biological metal ions. The fluorescent quenching is attributed to the formation of the coordinate covalent bonds between the Fe³⁺ and N-CDs, and the mechanism is proved to be a static type on the basis of the photoluminescence lifetime and the temperature-dependent fluorescent intensity change. Our eco-friendly and simple strategy will benefit the application of CDs in various fields.     

Complexes of Al(III) with d-gluconic acid

The complexation of Al(III) with d-gluconic acid was studied in solution by means of pH-potentiometry, ESI mass spectrometry and one- and two-dimensional NMR spectroscopy. Six complexes were found to form in solution from pH 2 to 10: [AlL]²⁺, [AlLH₋₁]⁺, [AlLH₋₂], [AlLH₋₃]⁻, [AlL₂H₋₁] and [AlL₂H₋₂]⁻. NMR spectroscopy indicated very complicated chemical exchange processes between the free ligand and gluconic acid molecules bound in the metal complexes, with different coordination modes resulting in changes both of the chemical shift and of the line shape of the signals. A solid complex [AlL₂H₋₁] · 2H₂O was isolated as a microcrystalline powder and characterized. The structures of the complexes are discussed on the basis of the spectroscopic results and MM force field calculations.     

Crystal structures and physico-chemical properties of Zn(II) and Co(II) tetraaqua(3-nitro-4-hydroxybenzoato) complexes: Their anticonvulsant activities as well as related (5-nitrosalicylato)–metal complexes

Purposes of these studies were to synthesize Zn(II) and Co(II) complexes of 3-nitro-4-hydroxybenzoic acid, determine their structures through X-ray crystallography, and obtain their anticonvulsant activities. Thermogravimetric, differential scanning calorimetry, impedance of aqueous solutions and magnetic properties analyses were also determined. Anticonvulsant and related activities of these complexes as well as Zn(II), Co(II), Ni(II) and Mg(II) (5-nitrosalicylato) complexes were determined by the National Institutes of Health, Antiepileptic Development Program. Results of these analyses are presented to document unique bonding features and physical properties of these compounds and their anticonvulsant activities. It is concluded that these compounds have chemical and physical properties that can be used to account for their anticonvulsant activities.     

Electrochemical Characteristics of Mediated Laccase‐Catalysis and Electrochemical Detection of Environmental Pollutants

Laccase has been immobilized on the carbon nanotubes modified glassy carbon electrode surface by adsorption. As‐prepared laccase retains good electrocatalytic activity to oxygen reduction by using 2,2′‐azino‐bis‐(3‐ethylbenzthiazoline‐6‐sulfonic acid) as the mediator. It can be used as a biosensor for the determination of catechol with broad linear range. Especially, azide, one of inhibitors of laccase, shows sensitive inhibition to catalytic activity of the laccase modified electrode. In addition, the inhibition by fluoride ions has also been studied. These demonstrate that the as‐prepared electrode can be used to detect halide and some the toxic pollutants, e.g., catechol and azide based on catalytic or inhibition reaction of laccase. The simple preparation procedure makes the system can be developed as non‐inhibition or inhibition biosensor.     

The Effects of the Modified Starches on the Melting Flow and Biodegradation of the Starch/Glycerol Blend

Summary: The purpose of this study was to improve the melting flow of starch/glycerol(GA) blends by modified starches. A variety of modified starches, which was treated by hydrolysis and acid hydrolysis, with and without ultrasonic treatment were used. The MFI (melt flow index) of blends increased from 0.5g/10min to 300g/10min when the addition of acid hydrolysis starch (0.3M CA-starch) was 70wt%. Their crystalline behaviors were analyzed by XRD results. The ultrasonic treatment has been proved to have the effect of hydrolysis without acids and synergistic effect on recrystalline. The SEM micrographs of the blend with the ultrasonic treatment starch gave the cleaving surface with comparison to the other blends. The weight loss of the blends with acid hydrolysis starches reached to 60∼80% after one week biodegradation as the ultrasonic treatment was used.     

聚乳酸纳米复合材料的研究进展

聚乳酸是一种重要的可生物降解/吸收高分子材料,广泛地用作可降解塑料、纤维和生物材料,市场前景广阔.它具有与聚烯烃相当的力学强度和加工性能,但耐热性和抗冲性较差.为满足各种应用的需要,其热性能、力学性能和气体阻隔性等尚需进一步提高.通过与无机纳米材料复合的方法,可以明显地提高聚乳酸的性能.本文介绍了近年来聚乳酸有机-无机纳米复合材料的制备、结构与性能等方面的研究进展,对三者的相互关系进行了评述,并对今后的研究方向进行了展望.     

A New Ent‐Trachylobane Diterpenoid from the Roots of Sapium Sebiferum

A new ent‐trachylobane diterpenoid, saposebifeic acid, together with thirteen known compounds, were isolated from the roots of Sapium sebiferum. Compounds, 5,7,8‐trimethoxycoumarin, baccatin, n‐alkyl trans‐ferulate and 2,6‐dimethoxyquinone, were reported for the first time from this plant. The structures of the new and known compounds were established on the basis of extensive 1D and 2D NMR spectral data.     

Adsorption Equilibrium and Kinetics of Egg-White Proteins on Immobilized Metal Ion Affinity Gels for Designing Fractionation

Designing an Immobilized Metal ion Affinity (IMA) chromatographic process on large scale demands a thorough understanding to be developed regarding the adsorption behaviour of proteins on metal loaded IMA (IMA-M(II)) gels and the characteristic adsorption parameters to be evaluated. This research investigation illustrates the significance of these aspects for the proposed fractionation of chicken egg-white proteins on these gels. Consequently, a systematic investigation of the adsorption characteristics of three chicken egg-white proteins viz., ovalbumin, conalbumin and lysozyme on Cu(II) and Ni(II) loaded IMA gels, iminodiacetate (IDA) and tris(2-aminoethyl)amine (TREN), has been undertaken. These gels differ in their selectivity towards the proteins of interest under the identical sets of experimental conditions. While TREN-Ni(II) was selective only for lysozyme, IDA-Cu(II), IDA-Ni(II) and TREN-Cu(II) showed varying affinities for all the three proteins. The equilibrium and kinetic data were analysed using various theoretical models and adsorption parameters were quantified. On the basis of these investigations, various strategies have been proposed for the efficient large-scale fractionation of chicken egg-white proteins on these gels.     

The use of thermal analysis in determination of some urinary calculi of calcium oxalate

The human urinary calculi are mainly constituted by calcium oxalate, magnesium ammonium phosphate hexahydrate, and uric acid. The ions or molecules are easily characterized by wet chemical methods. The difficulties appear in the differentiation of the hydrates of calcium oxalate (monohydrate COM or Whewellite, and dihydrate COD or Weddelite). A high level of COD in the urinary stones leads, often, inflammation, sharp pain and blood in urine. In the worse cases, they must be extracted by surgical way. The identification of the main components of urinary calculi, the knowledge of the true number of water molecules bounded to the calcium oxalate, and the determination of each hydrate in the mixture, are the interests of this memory. The thermal analysis (simultaneous DTA-TG) was applied on thirty-three urinary calculi. The determination of the calcium oxalate hydrates was confirmed by calorimetry (DSC). This revised version was published online in July 2006 with corrections to the Cover Date.