12-钼磷酸—聚乙烯醇的光电子转移反应

12-钼磷酸—聚乙烯醇体系具有不可逆光致变色的特性。根据X射线光电子能谱、电子自旋共振谱、紫外及可见光谱的测试结果,笔者认为:在PMo_(12)-PVA的光电子转移反应中,PMo_(12)既是氧化剂也是光敏剂。PMo_(12)分子中氧可分成O_p、O_b和O_t三种情况.其中O_t可成为光化学的活性位置,它和PVA羟基上的氧均较易被紫外光激活。激活的0_t边使周围的一个电荷向金属原子(Mo~(Ⅵ))转移,边与PVA羟基上被激活的氧作用,电子就由此羟基上的氧向O_t转移,致使体系中部分PMo_(12)与PVA发生二电子或四电子氧化还原反应,形成Mo(Ⅵ、Ⅴ)配合物而变色,同时,PVA分子的部分羟基及该羟基位的碳上脱氢形成羰基而具有酮结构。此外,从Mo(V)的ESR特征信号随时间变化而减弱,但其吸收光谱的吸光度未变,于是推断该光化学反应过程中尚有Mo(Ⅳ)生成,已由XPS谱证实。     

Totally selective ring-opening of amino epoxides with ketones: a general entry to enantiopure (2R,3S)- and (2S,3S)-3-aminoalkano-1,2-diols

[Reaction: see text] Transformation of enantiopure diastereoisomers (2R,1'S)- and (2S,1'S)-2-(1-aminoalkyl)epoxides into the corresponding 4-(1-aminoalkyl)-1,3-dioxolanes is achieved by reaction with different ketones in the presence of BF3.Et2O. The conversion takes place in very high yields, total selectivity, and without epimerization. A mechanism to explain this transformation is proposed. The obtained 1,3-dioxolanes can be deprotected, and (2R,3S)- and (2S,3S)-3-aminoalkano-1,2-diols were isolated.     

YPxV1—xO4（0≤x≤1）：Dy^3＋的合成及其光谱性质的研究

本文报道了不同组成的ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）：Ｄｙ＾３＋的合成和结构。ＹＰｘＶ１－ｘＯ４（０≤ｘ≤１）为四方晶系，晶胞参数随ｘ的增大呈线性减小。基质的Ｓｔｏｋｅｓ位移随ｘ的增大逐渐变大，而激发光谱峰值则向短波方向移动。在ＹＰｘＶ１－ｘＯ４：０．００６Ｄｙ＾３＋体系中，ｘ＞０．４时出现的基质发射是由ＰＯ＾３－４引起的。基质及Ｄｙ＾３＋的发光效率和Ｄｙ＾３＋的发光强度的黄蓝比均与ｘ有关。同时探     

The Studies of Lanthanide Shift Reagents in NMR Spectroscopy

The action of a series of lanthanide chelate complexes LnL₃, where Lu=La, Pr, Nd, Sm, Eu, Dy, Ho, Er and Yb; L= dbm (dibenzoylmethanato), dpm (dipivaloylmethanato), and acac acetylactonato), on nmr spectra of 2-butanol has been studied. The origin of shifting abilities and shifting sign of various lanthanide ions are explained by means of Bleaney's theory.     

Unique structural properties of the Mg-Al hydrotalcite solid base catalyst: an in situ study using Mg and Al K-edge XAFS during calcination and rehydration

The changes in the layered structure of Mg-Al hydrotalcite (Mg/ Al = 2) during heat treatment have been investigated by using in situ XAFS simultaneously at the Mg and Al K-edges. The development of unique in situ instrumentation allowed the coordination environments at both the Mg and Al centers to be monitored as a function of the temperature and heat treatment. The results of this study show that the hydrotalcite structure is highly flexible, and should lead to the further development of hydrotalcites as new solid basic catalysts. Moreover, the Mg and Al cations in the cation layers show different behavior as a function of temperature. The coordination of some octahedral Al ions decreases already at a temperature of 425 K, whereas the coordination about Mg does not show any modification at this temperature. However, hydrotalcite treated at 425 K, followed by cooling down to room temperature resulted in a complete reversal to the original octahedral Al coordination. It is proposed that Al-OH bond breakage occurs at 425 K, without the evolution of H2O. This bond is restored after cooling to room temperature. The actual dehydroxylation of hydrotalcite commences between 425 and 475 K, as indicated by a change in coordination of both the Mg and Al centers. This is accompanied by the evolution of H2O molecules and the changes are hence irreversible without the presence of excess water. Heat treatment at 725 K leads to the development of an MgO-like phase (octahedral Mg) and a mixed octahedral/tetrahedral Al phase. A subsequent rehydration at room temperature entirely restores the original coordination about the Al and Mg centers of hydrotalcite to a distance of 15 A, to which XAFS spectroscopy is sensitive.     

A novel route for waste water treatment: photo-assisted Fenton degradation of dye pollutants accumulated in natural polyelectrolyte microshells

The efficient accumulation of dyes in constructed natural polyelectrolyte microshells under moderate conditions, combined with the photo-assisted Fenton reagent, opens a new route for the effective elimination of dye pollutants from waste water.     

Separation of 99Mo from a simulated fission product solution by precipitation with a-benzoinoxime

The formation property of Mo precipitate was investigated and improved the existing process was using H₂O₂ that acts as an interfering compound in a subsequent alumina adsorption process. The property of the Mo precipitate was investigated by using SEM, FTIR, TG-DTA, and XRD. The simulated solution consisted of 1M nitric acid containing seven elements (Mo, I, Ru, Zr, Ce, Nd, Sr) and their radioactive tracers. As a result, the precipitate was composed of the Mo precipitate and re-precipitated a-benzoinoxime which was added excessively for increasing the precipitation efficiency. It was confirmed that the Mo precipitate was formed by the reaction of two a-benzoinoxime molecules and one MoO₂ ²⁺. Molybdenum precipitate was dissolved in 0.4M NaOH solution within 5 minutes without H₂O₂. Hydrogen peroxide induced only the rapid dissolution of the a-benzoinoxime re-precipitate. Also, the dissolution method without H₂O₂ was favorable in the purification aspect because Zr and Ru were contained as a small fraction of 1.3% and 7.7%, respectively, in the dissolving solution.     

Poly(dimethylsiloxane) microchip for precolumn reaction and micellar electrokinetic chromatography of biogenic amines

We have demonstrated that precolumn derivatization and capillary electrophoresis separation on a poly(dimethylsiloxane) (PDMS) microchip can be realized as efficient as those on glass microchips. In an optimized condition of micellar electrokinetic chromatography (MEKC), using 25 mM sodium borate buffer (pH 10.0) with 25 mM sodium dodecyl sulfate (SDS) and 5% v/v methanol, the electroosmotic flow in an oxidized PDMS microchip is stabilized within 3% for days. By employing a fluorometric derivatization with o-phthaldialdehyde (OPA) in an optimally designed reaction chamber, four most important biogenic amines occurring in foods, histamine, tyramine, putrescine, and tryptamine, are quantitatively determined in less than 1 min at the levels applicable to real samples. The migration behaviors of anionic OPA-derivatized biogenic amines under the MEKC conditions are analyzed, and it has been found that under our separation conditions, the electrophoretic mobility of the SDS micelles is significantly greater than those of the anions in the aqueous phase. The channel manifold in a PDMS substrate is fabricated using replica molding against a thick photoresist, SU-8, pattern generated by photolithography. The plate with the microchannel pattern is strongly, irreversibly bonded to another PDMS plate by using a new bonding technique, which employs surface oxidation by corona discharge generated from a cheap, handy source, Tesla coil.     

Paired Electrolysis of Aldoses in a Divided Flow Cell

Simultaneous anodic oxidation and cathodic reduction of aldoses in a divided flow cell were studied. The stream of the anolyte was an aqueous solution containing D-glucose, sodium bromide, and sodium bicarbonate. The stream of the catholyte was also an aqueous solution containing xylose and sodium sulfite. The factors which affected both the anodic and cathodic reactions were studied. The results indicate that the flow rates and temperatures of the anolyte and the catholyte, concentrations of the aldoses, pH values and the material of electrodes significantly affect both anodic and cathodic yields. The selectivities of gluconic acid in the anode and xylitol in the cathode were very high. The power consumption of paired electrolysis in the flow system was less than paired electrolysis in a batch system.     

Feature based fuzzy matching of 2D gel electrophoresis images

Automatic alignment (matching) of two-dimensional gel electrophoresis images is of primary interest in the evolving field of proteomics. In the present study, feature-based matching techniques, in their classical and robust versions, are described, and an automatic method of fuzzy alignment (FA) is introduced. This method allows automatic matching of two gel images with different numbers of features with unknown correspondence. Performance of FA is tested on simulated and real data sets.