Synthesis and Single-Crystal X-ray Structure of a Highly Symmetrical C60 Derivative, C60Br24

C(60) and liquid bromine react to form C(60)Br(24), a crystalline compound isolated as a bromine solvate, C(60)Br(24)(Br(2))(x), The x-ray crystal structure defines a new pattern of addition to the carbon skeleton that imparts a rare high symmetry. The parent C(60) framework is recognizable in C(60)Br(24), but sp(3) carbons at sites of bromination distort the surface, affecting conformations of all of the hexagonal and pentagonal rings. Twenty-four bromine atoms envelop the carbon core, shielding the 18 remaining double bonds from addition. At 150 degrees to 200 degrees C there is effectively quantitative reversion of C(60)Br(24) to C(60) and Br(2).     

Homogeneous catalysis in supercritical fluids

Supercritical fluids (SCFs), compounds heated and pressurized beyond the critical point, have many unusual properties. Homogeneous molecular catalysts, which have far greater control over selectivity than heterogeneous solid catalysts, are now being tested in SCFs, and early results show that high rates, improved selectivity, and elimination of masstransfer problems can be achieved. As industry moves away from toxic or environmentally damaging solvents, supercritical carbon dioxide may be an ideal replacement medium for nonpolar or weakly polar chemical processes. More than simply substitutes for nonpolar solvents, SCFs can radically change the observed chemistry. Supercritical carbon dioxide is also an excellent medium for its own fixation, as demonstrated by studies of its hydrogenation.     

植物精油的提取技术及在食品工业中的应用研究

植物精油具有抗菌消炎、防腐作用,在肉制品、果蔬制品、乳制品、水产品、焙烤制品等食品行业中得到了广泛的应用。综述了植物精油的提取技术,主要包括水萃取法、有机溶剂浸提法、超临界二氧化碳萃取法（SC-CO2）和无溶剂萃取法（压榨法、微波萃取和超声波萃取）等,并阐述了每一种技术的优缺点。     

正交试验法优化超临界CO_2萃取紫苏籽油的工艺及GC-MS成分分析(英文)

[目的]优化超临界CO_2法萃取紫苏籽油的条件,并分析紫苏籽油的化学成分。[方法]采用单因素和正交试验法优化萃取时间、萃取温度和萃取压强,用GC-MS分析紫苏籽油的化学成分组成。[结果]通过单因素和正交试验结果分析得到,最优紫苏籽油萃取条件为:萃取时间4h,萃取温度40℃,萃取压强23 MPa,在此条件下的得油率为12.43%。用GC-MS分析紫苏籽油化学成分,结果表明α-亚麻酸的含量达到76.183%。[结论]在试验所得条件下,可获得高质量和高纯度的紫苏籽油。     

超临界CO2萃取精馏技术在林蛙卵油脱腥中的应用研究

利用超临界CO2萃取-精馏技术,以林蛙卵油为原料,萃取获得林蛙卵油,以实现降低腥味目的。研究结果表明:在本实验采用的萃取精馏条件下,林蛙卵油得率受到的影响最小,腥味基本消除。     

Synthesis of fluoropolymers in supercritical carbon dioxide

Fluoropolymers are used in many technologically demanding applications because of their balance of high-performance properties. A significant impediment to the synthesis of variants of commercially available amorphous fluoropolymers is their general insolubility in most solvents except chlorofluorocarbons (CFCs). The environmental concerns about CFCs can be circumvented by preparing these technologically important materials in supercritical fluids. The homogeneous solution polymerization of highly fluorinated acrylic monomers can be achieved in supercritical carbon dioxide by using free radical methods. In addition, detailed decomposition rates and efficiency factors were measured for azobisisobutyronitrile in supercritical carbon dioxide and were compared to those obtained with conventional liquid solvents.     

Single crystal metals encapsulated in carbon nanoparticles

Single-domain microcrystals of LaC(2) encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La and C are the only elements present. Characteristic interatomic distances of 3.39 and 2.78 angstroms identify the compound inside the nanoparticle cavities as alpha-LaC(2), the phase of LaC(2) that is stable at room temperature. Bulk alpha-LaC(2) is metallic and hydrolytic. Observation of crystals of pure encapsulated alpha-LaC(2) that were exposed to air for several days before analysis indicates that the LaC(2) is protected from degradation bythe carbon polyhedral shells of the nanoparticles. A high percentage of the carbon nanoparticles have encapsulated LaC(2) single crystals. These carbon-coated metal crystals form a new class of materials that can be protected in their pure or carbide forms and may have interesting and useful properties.     

A gel partition model for organic desorption from a pond sediment

Adsorption at the water-sediment interface has been correlated with the organic carbon content of natural sediment samples and with water-octanol partitioning equilibria. In deriving a new model for sorption in sediment, it is assumed that adsorption is due to humin-kerogen polymers associated with the clay component in the sediment. The model includes solubility parameter theory applied to solute-gel-liquid interactions and a theory of the liquid-polymer interactions that control gel swelling. Partially swollen gels are expected to exhibit impeded diffusion. These concepts are able to explain observations of limited desorption of certain organic compounds from natural sediments and soil minerals. Experiments were performed in which extractive solvents flowed through a liquid chromatographic column packed with dried estuarine and pond sediment samples and the effluent was analyzed for a test lipophilic compound, di(2-ethylhexyl) phthalate. The model predicts that the maximum desorption rate and the maximum extent of gel swelling should coincide and, conversely, that the desorption rate should be diffusion-limited if the polymer gel is only partially swollen. The conditions for maximum desorption and for diffusion-limited desorption were both observed experimentally.     

Two-dimensional nanosheets produced by liquid exfoliation of layered materials

If they could be easily exfoliated, layered materials would become a diverse source of two-dimensional crystals whose properties would be useful in applications ranging from electronics to energy storage. We show that layered compounds such as MoS(2), WS(2), MoSe(2), MoTe(2), TaSe(2), NbSe(2), NiTe(2), BN, and Bi(2)Te(3) can be efficiently dispersed in common solvents and can be deposited as individual flakes or formed into films. Electron microscopy strongly suggests that the material is exfoliated into individual layers. By blending this material with suspensions of other nanomaterials or polymer solutions, we can prepare hybrid dispersions or composites, which can be cast into films. We show that WS(2) and MoS(2) effectively reinforce polymers, whereas WS(2)/carbon nanotube hybrid films have high conductivity, leading to promising thermoelectric properties.     

菹草红色类胡萝卜素结构的初步鉴定

 研究了从菹草中分离纯化的3个红色素组分r1、r2和r3的紫外可见吸收光谱、红外光谱、化学测试反应及质谱特性。结果表明,r1、r2和r3在丙酮、甲醇、乙醇、氯仿、二硫化碳中的可见吸收光谱均为平滑的、较对称的单峰(对应的峰波长为λmax),与角黄素、虾青素的相似,在正己烷中则呈现不对称"三指状"谱峰趋势,而β-胡萝卜素在正己烷等几种溶剂中可见吸收光谱则呈典型的"三指状"谱峰;与正己烷相比,随溶剂极性增强,λmax增大,溶剂对r1、r2和r3吸收光谱的形状、精细结构和λmax影响显著, r1、r2和r3的λmax平均值均比虾青素、角黄素和β-胡萝卜素的λmax平均值大。 不同溶剂中,r1、r2和r3的红外光谱显示出含羰基多烯化合物的特征峰（1 660～1 750 cm-1区域存在差异）。r1、r2和r3的化学测试反应也证明其分子中含羰基,而不含5,6 或 5,8-环氧基团。结合低分辨和高分辨电子轰击质谱 （EIMS）的测定分析,证明菹草红色素r1、r2和r3是分子式均为C40H50O2、分子量均为562且都含有羰基的类胡萝卜素,其结构不同于虾青素、角黄素和β-胡萝卜素,与紫杉红素(rhodoxanthin)的基本结构相同,是紫杉红素的同分异构体。     

Ultrafast viscous permeation of organic solvents through diamond-like carbon nanosheets

Chemical, petrochemical, energy, and environment-related industries strongly require high-performance nanofiltration membranes applicable to organic solvents. To achieve high solvent permeability, filtration membranes must be as thin as possible, while retaining mechanical strength and solvent resistance. Here, we report on the preparation of ultrathin free-standing amorphous carbon membranes with Young's moduli of 90 to 170 gigapascals. The membranes can separate organic dyes at a rate three orders of magnitude greater than that of commercially available membranes. Permeation experiments revealed that the hard carbon layer has hydrophobic pores of ~1 nanometer, which allow the ultrafast viscous permeation of organic solvents through the membrane.     

Perfluorocarbons having a short dwell time in the liver

Perfluorinated organic liquids are useful as high capacity oxygen and carbon dioxide solvents. After intravenous infusion most of these perfluorinated emulsions are deposited in the liver and spleen in a matter of days, where they remain for the lifetime of the animal. Hence, while they may be useful as isolated organ perfusion media their value as artificial blood is limited. A family of perfluorocarbons has now been discovered, which, although deposited in the liver after circulation in the blood, leave the liver to be excreted via the lungs and skin in a matter of days without apparent harmn to the animal.     

Cavitation-induced reactions in high-pressure carbon dioxide

The feasibility of ultrasound-induced in situ radical formation in liquid carbon dioxide was demonstrated. The required threshold pressure for cavitation could be exceeded at a relatively low acoustic intensity, as the high vapor pressure of CO2 counteracts the hydrostatic pressure. With the use of a dynamic bubble model, the formation of hot spots upon bubble collapse was predicted. Cavitation-induced radical formation was used for the polymerization of methyl methacrylate in CO2, yielding high-molecular-weight polymers. These results show that sonochemical reactions can be performed in dense-phase fluids, which allows the environmentally benign CO2 to replace conventional organic solvents in many reaction systems.     

Bromination of phenol red by the dogfish,Squalus acanthias

The uterus of the pregnant spiny dogfish, Squalus acanthias, can convert phenol red into a new purplish-blue dye. Evidence shows that the new dye is bromophenol blue. This is the first example of biological bromination that has been observed in a vertebrate.     

Arctic lakes and streams as gas conduits to the atmosphere: implications for tundra carbon budgets

Arctic tundra has large amounts of stored carbon and is thought to be a sink for atmospheric carbon dioxide (CO(2)) (0.1 to 0.3 petagram of carbon per year) (1 petagram = 10(15) grams). But this estimate of carbon balance is only for terrestrial ecosystems. Measurements of the partial pressure of CO(2) in 29 aquatic ecosystems across arctic Alaska showed that in most cases (27 of 29) CO(2) was released to the atmosphere. This CO(2) probably originates in terrestrial environments; erosion of particulate carbon plus ground-water transport of dissolved carbon from tundra contribute to the CO(2) flux from surface waters to the atmosphere. If this mechanism is typical of that of other tundra areas, then current estimates of the arctic terrestrial sink for atmospheric CO(2) may be 20 percent too high.     

Ionic liquid-mediated selective conversion of CO₂ to CO at low overpotentials

Electroreduction of carbon dioxide (CO(2))--a key component of artificial photosynthesis--has largely been stymied by the impractically high overpotentials necessary to drive the process. We report an electrocatalytic system that reduces CO(2) to carbon monoxide (CO) at overpotentials below 0.2 volt. The system relies on an ionic liquid electrolyte to lower the energy of the (CO(2))(-) intermediate, most likely by complexation, and thereby lower the initial reduction barrier. The silver cathode then catalyzes formation of the final products. Formation of gaseous CO is first observed at an applied voltage of 1.5 volts, just slightly above the minimum (i.e., equilibrium) voltage of 1.33 volts. The system continued producing CO for at least 7 hours at Faradaic efficiencies greater than 96%.     

由制浆黑液提取木质素制备活性炭

本试验采用酸析法提取草浆黑液中的木质素,以所提取的木质素为原料,添加ＺｎＣｌ２ 、ＣａＣｌ２为活化剂制备活性炭,所制备的活性炭得率高（ 达５０％ 以上） ,灰分低（ 仅为０１１３ ％ ） ,吸附性能与商品活性炭接近。从而减少了造纸黑液的排放     

液液萃取/气相色谱法测定废水中的三氯甲烷

建立了液液萃取/气相色谱法测定水中三氯甲烷的分析方法。选取石油醚、四氯化碳、环己烷、二硫化碳四种有机溶剂作为三氯甲烷萃取剂,确定了萃取方法和萃取次数,配制4种标准系列溶液,并对标准溶液和萃取溶液进行色谱分析。结果表明:4条标准曲线相关系数>0.9950,标准偏差<4%,加标回收率>75%。其中,石油醚的萃取效果最好为5.88 mg/ml,标准偏差为1.09%,加标回收率最高为99.21%,最低检出限为5.56×10-3mg/L。二硫化碳萃取效果最差为3.15 mg/ml,标准偏差为3.89%,加标回收率75.63%,最低检出限为9.58×10-2mg/L。环己烷和四氯化碳介于两者之间。该方法具有重现性好、准确度高、快速、简便的特点,为三氯甲烷的萃取研究提供一定的参考价值。     

Solvent dependence of the luminescence of N-arylaminonaphthalenesulfonates

N-Methyl,N-phenyl-2-aminonaphthalene-6-sulfonate, a fluorescence probe, adsorbs to cycloheptaamylose with a stoichiometry of 1 : 1. The fluorescence of the complex is similar to that observed when the dye is dissolved in organic solvents. Similar fluorescence is observed with the dye in ice. The results are interpreted in terms of "solvent" relaxation during the excited state lifetime of the dye.     

丁烯氟虫腈在油菜中残留分析方法的研究

在建立油菜中丁烯氟虫腈残留分析方法的实验中,在添加丁烯氟虫腈浓度为0.05、0.10、0.50μg/ml的油菜样品中分别加入60 ml不同提取溶剂,比较不同提取溶剂对丁烯氟虫腈残留添加回收率的影响。结果表明,乙腈提取效果最好。以乙腈为提取剂提取的丁烯氟虫腈残留液,通过柱层析(中性氧化铝与活性炭的混合物为柱填料)净化,气相色谱测定,得出氟虫腈的最小检测量为2×10-13g。油菜中丁烯氟虫腈(0.05~0.50 mg/kg)的添加回收率为91.12%~93.21%,变异系数是6.01%~13.20%。方法的准确性、灵敏度均达到农药残留分析的要求。