Eu1—xTbxBa2Cu3O7—δ中Tb离子价态的研究

研究了BaTbO_3、Tb_4O_7、TbFeO_3的Tb_(4d)XPS谱,找到了表征Tb~(3+)、Tb~(4+)的特征峰,得出的高、低结合能峰强之比与Tb~(4+)/Tb含量间的依赖关系,可用于确定Eu_(1-x)Tb_xBa_2Cu_3O_(7-δ)中“123”相的Tb离子混合价态,用常压高温烧结法,未能获得纯“123”单相,也不易获得纯利Tb~(3+)价态样品.在Eu_(1-x)Tb_xBa_2Cu_3O_(7-δ)中的Tb以Tb~(3+)、Tb~(4+)混合价态存在;当x=0.3时,Tb~(4+)/Tb=0.61.引入Tb~(4+)后“123”主相Cu(2)-O(2)平面上的O_(2p)空穴数降低,这是Tb~(4+)破坏超导电性的一种可能原因。     

聚丙烯熔体的零切变粘度与粘均分子量的关系

<正> 零切变粘度η_0是聚丙烯熔体流变性能的一个基本物理量,零切变粘度-分子量关系不仅具有理论上的兴趣,而且也有较大的实用意义。在文献中零切变粘度通常都是用毛细管粘度计数据外推求得的,但是由于聚丙烯熔体有较强的非牛顿性,即使在毛细管粘度计测量下限测得的粘度仍表现出明显的切变速率依赖性。因此,难于用外推的方法     

粘度法研究高分子溶液行为的实验改进(Ⅱ)

高分子在粘度计毛细管管壁上的吸附不仅会导致毛细管有效管径减小，而且可以导致毛细管界面性质发生显著改变，具体表现为测定高分子溶液流过时间t之前和之后纯溶剂的流过时间t0和t0′与高分子溶液流过时间t对浓度作图外推到浓度为零时的值t0^*并不一致。不同温度时聚乙烯吡咯烷酮（PVP）水溶液粘度测定结果表明，当吸附讷发子显著改变了毛细管界面性质时，需要将高分子溶液粘度测定方法由t/t0′改为t/t0^*。经过改进的粘度测定方法不仅更加普适合理，而且更加简单有效。     

邻苯二胺合钴氧合反应的研究Ⅰ 水溶液中配合物及其氧合配合物稳定常数的测定

自１９３８年Tsumaki报道犤１犦氧载体以来，这方面的研究已有很大进展犤２犦，只是理论研究居多。氧载体的氧合常数是氧载体研究中的一个重要参数，它的测定是氧载体研究中的一项重要内容，用pH电位法测定氧载体的氧合常数已有研究报道犤２～４犦，作者在研究中发现，邻苯二胺合钴（o－Phdn－Co）配合物在固相和水溶液中与O２反应时表现出很大差异，其反应产物的组成比分别为液相配合物Co∶O２＝２∶１，而固相配合物Co∶O２＝１∶２，为究其成因和进行理论探讨，有必要先测定其氧合常数。由于o－Phdn－Co配合物的配位常数也未见文献…     

Reduction of 4-nitrophenol catalyzed by nitroreductase

The reduction of 4-nitrophenol catalyzed by nitroreductase in the presence of NADH was investigated in this paper.4-Amino- phenol and 4-bydroxylamino-phenol were found in the reductive products.The relationship between reaction time and the reductive ratio were studied.The similar reducing ratios of 4-nitrophenol were obtained under aerobic and anaerobic conditions.The results indicated that an oxygen-insensitive reaction was proceeded in the reduction of 4-nitrophenol and nitroreductase was an oxygen- insensitive enzyme.The reductive products of 4-nitrophenol were determined by HPLC and MS.     

超声辐射下某些含官能团化合物与二氯卡宾的反应

超声辐射在有机反应中的应用日趋广泛。我们曾报道了超声辐射与相转移催化相结合产生二氯卡宾和二溴卡宾的方法及其与烯烃加成反应的结果。该法比单纯使用相转移催化剂或超声辐射更为可取。本文进一步将它用于二氯卡宾与某些含官能团化合物的反应,考察超声辐射的影响。反应是在固-液两相条件下进行的,即以粉末状氢氧化钠为碱,氯仿过量兼作溶剂。结果表明,超声辐射对各类化合物反应的影响有相当明显的差异。     

Efficient photochemical oxetane formation from 1-methyl-2,4,5-triphenylimidazole and benzophenones

In contrast to simple imidazoles, 1-methy1–2,4,5-triphenylimidazole ($\text{1}$) produced stable oxetane photoadducts $\text{3b}$ - $\text{e}$ with good efficiency upon irradiation in the presence of benzophenone derivatives $\text{2b}$ - $\text{e}$ in acetonitrile solution. Irradiation in the solid-phase was also studied. The oxetanes $\text{3b}$ - $\text{e}$ readily underwent cycloreversion by acid catalysis or by heating.     

Photochemistry of nonconjugated bichromophoric systems III. Synthesis and photoreaction of poly(ethylene glycol) biscoumarinyloxyacetates

A series of poly(ethylene glycol) biscoumarinyloxyacetatea have been synthesized and their intramolecular photochemical cyclodimerizations have been studied. It was found that only syn-HT configuration products were obtained when these bisesters were directly irradiated in chloroform, and the yields of the products decreased with the increase of the chain length. This photocyclization reaction is a convenient and effective method to synthesize macrocyclic compounds.     

Surface-enhanced Raman scattering (SERS) from different azobenzene self-assembled monolayers and sandwiches

Self-assembled monolayers (SAMs) of functionalized azobenzene thiols (RAzoCnSH, n=3-6 for R=H, abbreviated as AzoCnSH; and n=4 for R=CH(3)CONH, abbreviated as aaAzoC4SH) on different substrates RAzoCnSz.sbnd;z.sfnc;S (S represents substrates of vacuum-deposited gold (Au), silver foil (Ag), HNO(3) etched silver foil (EAg), and silver mirror (mAg)) have been studied by SERS in the near-infrared region. SERS of the SAMs on EAg and/or mAg exhibit SERS effects that vary with etching time and/or deposition time. The most appropriate time is 5 s for etching in 1:1 HNO(3) and 40 s for deposition in 0.1 M Ag(NH(3))(2)NO(3). Further, a layer of Ag mirror was conveniently deposited on the top of the SAMs on different substrates, yielding a more efficient SERS-active system possessing a "sandwiched" structure of mAgz.sfnc;RAzoCnS-z.sfnc;S. An appropriate surface roughness is required for the strongest SERS effect. Scanning electron microscopy (SEM) indicates that there exist a large number of projects around 100 nm on the surface showing the strongest SERS effect. When the surface roughness is decreased or increased, the SERS effect decreases sharply. The relationship between the SERS effect and the structural nature was investigated and showed that the enhancement factor decays exponentially with increasing in distances of the azobenzene group from the underlying substrate or the overlying silver mirror. This result reveals that the SERS effect may be the result of the electromagnetic coupling effect between two metal layers.     

螺［异苯并呋喃－1（3H），9＇－（9H）－2＇－N，N－二苄胺基－6＇－二乙胺基占吨］－酮－3的合成及晶体结构研究

合成了螺［异苯并呋喃－１（３Ｈ），９＇－（９Ｈ）－２＇－Ｎ，Ｎ－二苄胺基－６＇－二乙胺基占吨］－酮－３，Ｃ＿（３７）Ｈ＿（３４）Ｎ＿２Ｏ＿３，单斜晶系，空间群Ｃｃ，晶体学参数为ａ＝１６．８２６（４），ｂ＝１０．６４８（４），ｃ＝１７．６１８（７），β＝９２．２５（２）°，Ｖ＝３１５４（２），Ｚ＝４，Ｍ＿ｒ＝５６６．７，Ｄ＿ｘ＝１．１９ｇ／ｃｍ３，Ｆ（０００）＝１２００。结构由直接法解出，偏离因子Ｒ＝０．０８０。分子由占吨和异苯并呋喃两部分组成Ｙ形结构，占吨部分相连的苄基的两个苯环位于占吨部分的两侧。