活性氮与溴分子反应的实验研究

在流动反应管中, 利用高纯N₂空心阴极放电制备活性氮, 研究了活性氮与溴分子碰撞反应得到的发射光谱. 在540～800 nm波段观察到了较强的NBr(b¹Σ^＋→X³Σ^－)跃迁发射谱, 在292 nm处观察到了Br₂(D'→A')辐射跃迁. 实验结果表明, 得到的NBr(b¹Σ^＋)显示出了非弛豫的发射特征, 最高振动能级为ν'＝9. 激发态的NBr(b¹Σ^＋)是由活性氮中的N(²P)原子与Br₂直接反应生成的.     

La1—xMxFeyCo1—yO3型复合氧化物（M=Sr,Ba）的合成,结构及电性能

钙钛矿型的稀土与过渡金属复合氧化物(ABO_3)及部分稀土为碱土金属置换的A_(1-x)M_xBO_3型复合物在最近20年来研究较多,并在催化气敏,超导等方面取得了良好进展。但对A_(1-x)M_xB_(1-y)N_yO_3型复合物却研究甚少。本文合成了一系列的La_(1-x)M_xFe_yCo_(1-y)O_3(M=Sr或Ba)钙钛矿型复合氧化物,研究了它们组成与电性的变化规律。     

Chemical Reactivities of Magnesium Nanopowders

The chemical reactivities of two forms of superfine magnesium powders differing in particle size are compared with commercial magnesium powder for nitridation, hydrogenation and Grignard reactions. The chemical reactivities of these magnesium powders are approximately proportional to their specific surface areas or their reciprocal particle diameters. Since the magnesium nanopowders give a specific surface area around three orders of magnitude larger than that of the commercial ones, they can undergo reactions under mild conditions at which the extent of reaction of the commercial magnesium powder is too small to be measured.     

稀土氯化物催化作用下纳米氢化钠对芳基卤化物的还原脱卤

稀土氯化物催化作用下纳米氢化钠对芳基卤化物的还原脱卤＊张源魁廖世健＊＊徐筠余道容（中国科学院大连化学物理研究所，大连１１６０２３）沈琪（苏州大学化学化工学院，苏州２１５００６）关键词催化还原脱卤，稀土氯化物，氢化钠，双金属协同效应有机卤化物的还原脱卤...     

An albumin-based gold nanocomposites as potential dual mode CT/MRI contrast agent

In pursuit of the biological detection applications, recent years have witnessed the prosperity of novel multi-modal nanoprobes. In this study, biocompatible bovine serum albumin (BSA)-coated gold nanoparticles (Au NPs) containing Gd (III) as the contrast agent for both X-ray CT and T₁-weighted MR imaging is reported. Firstly, the Au NPs with BSA coating (Au@BSA) was prepared through a moderate one-pot reduction route in the presence of hydrazine hydrate as reducer. Sequentially, the BSA coating enables modification of diethylenetriaminepentaacetic acid (DTPA) as well as targeting reagent hyaluronic acid (HA), and further chelation of Gd (III) ions led to the formation of biomimetic nanoagent HA-targeted Gd-Au NPs (HA-targeted Au@BSA-Gd-DTPA). Several techniques were used to thoroughly characterize the formed HA-targeted Gd-Au NPs. As expected, the as-prepared nanoagent with mean diameter of 13.82 nm exhibits not only good colloid stablility and water dispersibility, but also satisfying low cytotoxicity and hemocompatibility in the tested concentration range. Additionally, for the CT phantoms, the obtained nanocomplex shows an improved contrast in CT scanning than that of Au@BSA as well as small molecule iodine-based CT contrast agents such as iopromide. Meanwhile, for the T₁-weighted MRI images, there is a linear increase of contrast with concentration of Gd for the two cases of HA-targeted Gd-Au NPs and Magnevist. Strikingly, the nanoagent we explored displays a relatively higher r₁ relaxivity than that of commercial MR contrast agents. Therefore, this newly constructed nanoagent could be used as contrast agents for synergistically enhanced X-ray CT and MR phantoms, holding promising potential for future biomedical applications.     

Extremely bulky triarylphosphines incorporating 2,6-diisopropylphenyl substituents; consideration of steric shielding and steric pressure

The geometry of 15 triarylphosphines which differ in the nature of the substituents at the 2 and 6 positions of one or more phenyl rings are compared. The sum of angles around phosphorus, ∑{∠CPC}, is used as the primary measure of steric bulk. The roles of substituents, which act as steric shields surrounding the phosphine lone pair and of those which generate steric pressure and cause flattening of the C₃P pyramid are identified. Both crystallographic and computational (HF 6-31G(d)) structures are used to assess ∑{∠CPC}, the pyramidalization angle α, the average C-P distance, and the helical twist angle of the aryl rings β. All of these parameters confirm that ortho-2,6-diisopropyl substituted aryl groups generate the most sterically congested triarylphosphines. Comparison to Tolman cone angles are made where these are available.