微波法制备聚(苯乙烯-N-异丙基丙烯酰胺)热敏性微球

聚(N-异丙基丙烯酰胺)(PNIPAM),由于其大分子链上同时具有亲水性的酰氨基和疏水性的异丙基,使得PNIPAM的水溶液,在32℃附近具有最低临界溶液温度(LCST)．PNIPAM及其共聚物表现出相转变,产生热敏性质．利用PNIPAM的热敏性质,可以制备多种智能高分子材料．这些高分子材料在生物医学、免疫分析、     

Alginate-enfolded copper hexacyanoferrate graphene oxide granules for adsorption of low-concentration cesium ions from aquatic environment

Alginate-enfolded copper hexacyanoferrate (CuHCF) graphene oxide granules (CGAGs) were prepared and showed excellent mechanical strength and water-swelling resistance. The maximum adsorption capacity was 50.5 mg/g. The distribution coefficient reached the maximum at pH 5.0, and was almost unaffected by the coexisted metal ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, less than 20 mg/L). With the flow rate of 1.2 mL/min and the feed concentration of 20 mg/L, the efficiency of the fixed-bed column was calculated as 60.6%. These results suggested that CGAGs could be an alternative adsorbent for removing low-concentration cesium from the contaminated potable water and surface water so on.

     

Synthesis of novel 5-O-(6′-O-modified)-desosamine 14-membered ketolides

A new and facile procedure was developed to synthesize novel 5-0- (6′-O-modified)-desosamine 14-membered ketolides by adopting different protective strategies and comparing various glycosylation conditions. Two trichloroacetimidate donors, with Lev or Ac substituent groups at the C-6 position, were synthesized to couple with the erythronolide. Several novel 5-0- (6′-O-modified)-desosamine 14-membered ketolides were obtained to verify the utility of the method.     

面心立方双层铁磁薄膜中低能量体模的波形演化

利用二次量子化方法研究了由相同面心立方结构(100)材料构成的铁磁性双层薄膜中的自旋波,重点讨论了低能量体模的波形演化情况.结果表明,面心立方晶格能量较低的体模在薄膜A-A型铁磁材料传播过程中波形完全相同,传播行为也完全相同;并且随着能量的增加,体模波长在两层铁磁薄膜材料中逐渐缩短,波速逐渐减小.     

Preparation and electrochemical properties of Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript>/Ti<Subscript>4</Subscript>O<Subscript>7</Subscript> composite for lithium-ion batteries

In order to improve the rate capability of Li₄Ti₅O₁₂, Ti₄O₇ powder was successfully fabricated by improved hydrogen reduction method, then a dual-phase composite Li₄Ti₅O₁₂/Ti₄O₇ has been synthesized as anode material for lithium-ion batteries. It is found that the Li₄Ti₅O₁₂/Ti₄O₇ composite shows higher reversible capacity and better rate capability compared to Li₄Ti₅O₁₂. According to the charge-discharge tests, the Li₄Ti₅O₁₂/Ti₄O₇ composite exhibits excellent rate capability of 172.3 mAh g^?1 at 0.2 C, which is close to the theoretical value of the spinel Li₄Ti₅O₁₂. More impressively, the reversible capacity of Li₄Ti₅O₁₂/Ti₄O₇ composite is 103.1 mAh g^?1 at the current density of 20 C after 100th cycles, and it maintains 84.8% of the initial discharge capacity, whereas that of the bare spinel Li₄Ti₅O₁₂ is only 22.3 mAh g^?1 with a capacity retention of 31.1%. The results indicate that Li₄Ti₅O₁₂/Ti₄O₇ composite could be a promising anode material with relative high capacity and good rate capability for lithium-ion batteries.     

Molecular rectification in a metal-insulator-metal junction based on self-assembled monolayers

An electrical junction formed by mechanical contact between two self-assembled monolayers (SAMs)--a SAM formed from an dialkyl disulfide with a covalently linked tetracyanoquinodimethane group that is supported by silver (or gold) and a SAM formed from an alkanethiolate SAM that is supported by mercury-rectifies current. The precursor to the SAM on silver (or gold) was bis(20-(2-((2,5-cyclohexadiene-1,4-diylidene)dimalonitrile))decyl)) disulfide and that for the SAM on mercury was HS(CH(2))(n-1)CH(3) (n = 14, 16, 18). The electrical properties of the junctions were characterized by current-voltage measurements. The ratio of the conductivity of the junction in the forward bias (Hg cathodic) to that in the reverse bias (Hg anodic), at a potential of 1 V, was 9 +/- 2 when the SAM on mercury was derived from HS(CH(2))(15)CH(3). The ratio of the conductivity in the forward bias to that in the reverse bias increased with decreasing chain length of the alkanethiol used to form the SAM on mercury. These results demonstrate that a single redox center asymmetrically placed in a metal-insulator-metal junction can cause the rectification of current and indicate that a fixed dipole in the insulating region of a metal-insulator-metal junction is not required for rectification.     

医药中间体阿糖腺苷的制备方法研究进展

阿糖腺苷是一种广谱的DNA病毒抑制剂,在临床上可用于治疗单纯疱疹病毒性脑炎。其衍生物如单磷酸阿糖腺苷、氟达拉滨也在相关疾病治疗方面疗效显著。阿糖腺苷的制备方法包括化学合成法和生物合成法,化学合成法原料多变、合成方法多样;生物合成法的研究集中在酶法,关键工艺在于酶的制备。本文综述了阿糖腺苷制备方法最新研究进展,并展望了其应用前景。     

二维分子筛的制备及其催化应用研究进展

沸石分子筛是一种具有独特孔道结构的硅铝酸盐晶体,因其具有较大的比表面积、优异的孔道择形性、良好的热稳定性以及适宜的酸性质等特点,被广泛应用于催化、吸附、分离等领域。与常规三维沸石分子筛相比,二维分子筛由于其独特的形貌结构带来的可调变的多级孔结构、适宜的表面酸性以及良好的扩散传质性能等优点,已在吸附和催化领域显示出巨大的应用潜力。本文系统总结了二维MFI、SAPO-34、MCM-n、Y型分子筛等的合成以及此类分子筛催化应用研究方面的最新进展。最后,对二维沸石分子筛材料的新合成方法及新应用领域进行了展望。     

One-pot synthesis of trans-β-lactams from ferrocenylketene generated by thermal Wolff rearrangement

A series of β-lactams containing the ferrocene moiety were synthesized through the Staudinger reaction between ferrocenylketene generated by the thermal Wolff rearrangement of the corresponding diazo ketone and various imines. The stereochemical outcome has been investigated and the trans-products were isolated as the main products, opposite to the reported results by Bonini and coworkers. The absolute configuration of (±)-trans-1,4-diphenyl-3-ferrocenylazetidin-2-one (3c) was determined by X-ray analysis. The stereoselectivity is discussed from the viewpoint of the reaction mechanism.     

σ‐Aromaticity in an Unsaturated Ring: Osmapentalene Derivatives Containing a Metallacyclopropene Unit

In general, aromaticity can be clarified as π‐ and σ‐aromaticity according to the type of electrons with major contributions. The traditional π‐aromaticity generally describes the π‐conjugation in fully unsaturated rings whereas σ‐aromaticity may stabilize fully saturated rings with delocalization caused by σ‐electron conjugation. Reported herein is an example of σ‐aromaticity in an unsaturated three‐membered ring (3 MR), which is supported by experimental observations and theoretical calculations. Specifically, when the 3 MR in cyclopropaosmapentalene is cleaved by ethane through two isodesmic reactions, both of them are highly endothermic (+29.7 and +35.0 kcal mol^?1). These positive values are in sharp contrast to the expected exothermicity, thus indicating aromaticity in the 3 MR. Further nucleus‐independent chemical shift and anisotropy of the current‐induced density calculations reveal the nature of σ‐aromaticity in the unsaturated 3 MR.