使用助磨剂解决金矿样品制样的均匀性

文章提出对含有明金而脉石硬度低的岩石样品采用加入高硬度的石英砂作为助磨剂,将明金充分粉碎,使制成的金矿样品的均匀性和代表性符合地质样品加工规范要求。通过对部分天然样品及人工合成样品制样测试验证,效果良好。     

基于Si基沉积拉曼增强活性Au膜的制备与表征

研究了一种新的表面增强拉曼活性Au基底的制备方法,采用无电镀沉积方法,通过HF和HAuCl4的混合溶液对Si片进行处理获得具有不同形貌的Si基Au膜,利用扫描电子显微镜(SEM)分析了基底的表面形态和结构,测定结晶紫分子在基底表面的拉曼光谱。结果表明,Si基Au膜表面的表面增强拉曼散射(SERS)增强随制备时间的增加呈现先增强后减弱的趋势,增强效果优于常用的Au胶体系,是一种非常高效的拉曼活性增强基底。     

A Three‐Dimensional Gold‐Decorated Nanoporous Copper Core–Shell Composite for Electrocatalysis and Nonenzymatic Biosensing

Bimetallic core–shell nanostructures have attracted increasing attention due to their low material costs along with enhanced chemico‐physical properties in comparison with their monometallic counterparts. Here, a novel gold‐decorated nanoporous copper (Au@NPC) core–shell composite fabricated by a facile in situ hydrometallurgy approach is reported. Thin gold shells with a controllable thickness are homogeneously deposited onto the internal surfaces of 3D nanoporous copper via a spontaneous displacement reaction while nanoporous copper is utilized as a reduction agent as well as 3D template and substrate. The resulting inexpensive core–shell nanostructure exhibits significant electrocatalytic activity for the oxidation of methanol and high non‐enzymatic sensitivity in detecting glucose.     

Organocatalyzed Conjugate Addition of Carbonyl Compounds to Nitrodienes/Nitroenynes and Synthetic Applications

The purpose of this study is to point out the synthetic utility of a new class of Michael acceptors (nitrodienes and nitroenynes). The highly enantioselective organocatalytic Michael addition of carbonyl compounds to these functionalized nitroolefins has been carried out in the presence of (S)‐diphenylprolinol silyl ether to achieve some interesting building blocks in high selectivities. The adducts thus obtained can be easily converted by taking advantage of the corresponding unsaturated carbon‐carbon bond. In presence of the double bond, metathesis or electrophilic activation could be carried out whereas in the presence of the triple bond electrophilic activation could be conducted. We thus focused on a gold‐catalyzed cyclization of the bis‐homopropargylic alcohol to afford the corresponding substituted tetrahydrofuran. Then, we also demonstrated that organic and gold catalysts were compatible in a one‐pot process. Indeed, we developed a one‐pot enantioselective organocatalytic Michael addition to a nitroenyne followed by a gold‐catalyzed acetalization/cyclization to achieve tetrahydrofuranyl ethers in high diastereo‐ and enantioselectivities with excellent yields.     

Scope and Limitations of Palladium‐Catalyzed Cross‐Coupling Reactions with Organogold Compounds

Five different alkenylgold(I) phosphane complexes were prepared and then investigated in [1,1′‐bis(diphenylphosphino)ferrocene]palladium(II) dichloride‐catalyzed cross‐coupling reactions with different aryl halides, heterocyclic halides, an alkenyl halide, an alkynyl halide, allylic substrates, benzyl bromide and an acid chloride. With regard to the halides, the iodides were highly reactive, bromides or chlorides gave significantly reduced yields or failed, allylic acetates failed, too. The cross‐coupling partners contained a number of different functional groups, while free carboxylic acids did not deliver cross‐coupling products and o,o‐disubstituted arenes failed as well, a broad range of other functional groups like nitro groups, nitrile groups, ester groups, α,β‐unsaturated ester groups and lactones, aldehydes, alkoxy groups, pyridyl groups, thienyl groups, unprotected phenols and anilines, even aryl azides were tolerated. The structures of one alkenylgold(I) species and of four of the cross‐coupling products were proved by crystal structure analyses.     

Size charge fractionation of metals in municipal solid waste landfill leachate

Municipal solid waste landfill leachates from 9 Norwegian sites were size charge fractionated in the field, to obtain three fractions: particulate and colloidal matter >0.45microm, free anions/non-labile complexes <0.45microm and free cations/labile complexes <0.45microm. The fractionation showed that Cd and Zn, and especially Cu and Pb, were present to a large degree (63-98%) as particulate and colloidal matter >0.45microm. Cr, Co and Ni were on the contrary present mostly as non-labile complexes (69-79%) <0.45microm. The major cations Ca, Mg, K, and Mn were present mainly as free cations/labile complexes <0.45microm, while As and Mo were present to a large degree (70-90%) as free anions/non-labile complexes <0.45microm. Aluminium was present mainly as particulate and colloidal matter >0.45microm. The particulate and colloidal matter >0.45microm was mainly inorganic; indicating that the metals present in this fraction were bound as inorganic compounds. The fractionation gives important information on the mobility and potential bioavailability of the metals investigated, in contrast to the total metal concentrations usually reported. To study possible changes in respective metal species in leachate in aerated sedimentation tanks, freshly sampled leachate was stored for 48h, and subsequently fractionated. This showed that the free heavy metals are partly immobilized during storage of leachate with oxygen available. The largest effects were found for Cd and Zn. The proportion of As and Cr present as particulate matter or colloids >0.45microm also increased.     

Differences in content and composition of free lipids and carotenoids in flour of spring and winter wheat cultivated in Poland

The work presents the content and composition of free lipids and carotenoids in spring and winter classes of wheat flour. It discusses genetical and physiological aspects of their synthesis and accumulation in wheat kernels and also indicates how methodological differences explain differences in results presented in the literature. It has been reported that spring wheat flours are richer in free lipids, especially in the non-polar fraction. The content of glycolipids ranged from 134 to 215 mg/100 g flour and was more stable within the winter wheat class. The percentages of the two main fractions, namely DGDG and MGDG, were similar in both wheat classes and reached ca. 77%. Phospholipids constituted the smallest fraction of the flour free lipids in both wheat classes; however, spring wheat flours were richer in these compounds, which is likely associated with a greater content of spherosomes in the endosperm of this wheat class. The free lipids of spring wheat flour contained more oleic and slightly less linoleic and linolenic acids. Spring wheat flour was also richer in carotenoids, although there were varieties in both classes that deviated from this. The main carotenoid was lutein, whose total percentage in the form of different isomers ranged from 71.3% to 83.3% and was slightly lower for spring wheat flour. Lutein, in the form of a trans-isomer, constituted about 62% and 70% of all carotenoids in spring and winter wheat flours, respectively.