四苯硼钠-甲苯胺蓝缔合物纳米微粒体系减色效应研究

在PH4.0醋酸-醋酸钠介质中，甲苯胺蓝在600nm处有一个吸收峰，随着四苯硼钠浓度的增大甲苯胺蓝在600nm处吸收峰降低，颜色减弱，这是由于甲苯胺蓝-四苯硼钠缔合物分子间存在较强的疏水作用及分子间作用力，聚集形成纳米微粒所致，甲苯胺蓝-四苯硼钠纳米微粒体系亦在600mm处有1个吸收峰，在400mm、470mm和580mm处产生3共振散射峰，其中400mm和580mm为甲苯胺蓝-四苯硼钠复合纳米微粒产生的特征共振散射峰，这也表明有纳米微粒存在，丙酮浓度的影响实验结果等表明，纳米微粒的形成是产生其减色效应的原因。     

Studies on the Distribution of Phenoxyacetic Acid in Two-Phase Systems: <Emphasis Type="Italic">n</Emphasis>-Aliphatic Hydrocarbon – Water

Summary. Phenoxyacetic acid distribution in two-phase systems n-aliphatic hydrocarbon (C₅–C₈) – water and its dimerization in organic phase were investigated. The values of distribution coefficient (D _HR), distribution constant (K _D), and dimerization constant (K _dim) of acid were obtained. The empirical correlations of these quantities with Hildebrand solubility parameter of organic solvents were established. The influence of pH of the aqueous phase as well as the polarity of the applied organic solvents on phenoxyacetic acid physical chemistry in the two-phase systems was described.     

Insoluble polystyrene-bound quaternary onium salt catalysts for the synthesis of cyclic carbonates by the reaction of oxiranes with carbon dioxide

The addition reaction of oxiranes ( 26a—e ) with carbon dioxide (CO₂) was performed using insoluble polystyrene beads containing pendant quaternary ammonium or phosphonium salts as catalysts under atmospheric pressure. The reaction of 26a—e with CO₂ proceeded smoothly catalyzed by 1–2 mol % of the polymer-supported quaternary onium salts to give the corresponding cyclic carbonates ( 27a—e ) in high yields at 80–90°C. In this reaction system, the catalytic activity of the polymer-supported quaternary onium salts was strongly affected by the following factors: degree of ring substitution (DRS) of the onium salt residues to the polymer, degree of crosslinking (DC) of the polystyrene beads, chain length of the alkylene spacer between the polymer back-bone and the onium salt, hydrophobicity of the alkyl group on the onium salts, and kind of onium salts. That is, the polymer-supported quaternary phosphonium salts with low DRS and DC and with long alkylene spacer chain were found to have higher catalytic activity than low molecualr weight quaternary onium salts. The above polymer-supported catalysts can easily be separated at the end of a reaction by filtration and can be reused for at least seven runs. It was also found that the rate of reaction was proportional to the products of catalyst concentration and oxirane concentration. © 1993 John Wiley & Sons, Inc.     

Nanowire‐Based Electrochemical Biosensors

We review recent advances in biosensors based on one‐dimensional (1‐D) nanostructure field‐effect transistors (FET). Specifically, we address the fabrication, functionalization, assembly/alignment and sensing applications of FET based on carbon nanotubes, silicon nanowires and conducting polymer nanowires. The advantages and disadvantages of various fabrication, functionalization, and assembling procedures of these nanosensors are reviewed and discussed. We evaluate how they have been used for detection of various biological molecules and how such devices have enabled the achievement of high sensitivity and selectivity with low detection limits. Finally, we conclude by highlighting some of the challenges researchers face in the 1‐D nanostructures research arena and also predict the direction toward which future research in this area might be directed.     

The “Facilitated Transition” hypothesis as an explanation for the gemdialkyl effect

A new technique of searching the conformational space of transition states was used to explore the cause of the rate acceleration in the gem-dialkyl effect in intramolecular cyclization reactions. Several previous hypotheses were discarded and a new hypothesis was advanced based on this new data. This hypothesis, the “Facilitated Transition” hypothesis, states that increased steric hindrance reduces the overall activation energy by facilitating rotation through the transition state. The older “Reactive Rotamer” hypothesis was eliminated by generating all conformations of the starting materials using the and computer programs and demonstrating that no relationship is found between rate increase and a change in the concentration of “reactive rotamers”.     

分子诱导效应指数与链烷烃的沸点

利用基团的诱导效应指数，首次提出了分子的诱导效应指数的概念，并定义了 链烷烃的有效碳链长度NC＝（MIs,N/MIb,N)·N，式中MIs,N,MIb,N分别为直链和支 链异构体的分子诱导效应指数。研究结果表明，链烷烃的沸点Tb(℃）与NC关系是 ：1n(806.5-Tb)=6.9824-0.11431NC^2/3     

Photo-initiated base-formation in a polymer matrix

It was found that amines were formed efficiently by the photolysis of O-acyloximes followed by hydrolysis in polystyrene films and the relationship between structures of O-acyloximes and yields of amines were investigated. O-phenylacetyl acetophenone oxime (PaApO), O-pivaloyl acetophenone oxime (PApO), and O-benzoyl acetophenone oxime (BApO) as monofunctional O-acyloximes and O,O′-succinyl diacetophenone oxime (SDApO) and O,O′-glutaryl diacetophenone oxime (GDApO) as bifunctional O-acyloximes were examined. The yields of amines for PaApO and SDApO under N₂ were ca. 70%, which was the highest among O-acyloximes examined in this experiment. On the other hand, the yields for PApO, BApO, and GDApO were less than 15% and it was verified that the hydrogen abstraction by imino radicals via 6-membered cyclic intermediates resulted in the lowering of yields. Although the effect of oxygen under photolysis on the yields of amine for PaApO was negligible under 50% conversion of PaApO, the yield decreased with further increase in the conversion and was 50% at 90% conversion. © 1994 John Wiley & Sons, Inc.     

微生物法分析天然抗氧化剂性能

建立了微生物抑菌活性纸片试验法，对葛根黄酮、诃子提取物、丹皮酚、竹叶黄酮等4种天然抗氧化剂的抗氧化性能进行了研究。竹叶黄酮、诃子、葛根具有较强的抗单线态氧能力，而丹皮酚抗单线态氧的能力较差。在不同的氧化还原微环境下，天然抗氧化剂可能表现出抗氧化能力，亦可能表现出促氧化能力，二者有着不同的反应机理。微生物抑菌活性纸片法可作为研究较复杂生物环境中抗氧化剂性能的一种简便方法。     

高活性的茂基钛配合物／正丁基锂加氢催化体系的研究

考察了茂环上不同取代基及钛上阴离子配体对茂基钛配合物／正丁基锂催化体系加氢活性和稳定性的影响。在充分发挥该体系催化活性的条件下，由配合物Ｃｐ２ＴｉＣｌ２、Ｃｐ２ＴｉＦ２和Ｃｐ２Ｔｉ［ＯＣ６Ｈ３（ＣＨ３－２）Ｃｌ－４］２组成的催化体系对辛烯－１加氢的最高活性（或初活性）达到４６￣５８ｓ＾－１。     

Electrochemical studies of Tl(I) crown-ether complexes in nonaqueous media

Summary Complexation equilibria of the Tl(I) ion with 18-crown-6 and dibenzo-18-crown-6 were studied polarographically in 10 nonaqueous solvents. The stability of the complexes is strongly influenced by the nature of solvents and varies with their Lewis basicities. It has been found that the logK _s value (K _s is the stability constant of the complex) can be well described by empirical relation logK _s=a DN+b, whereDN stands for the Gutmann donor number anda andb mark the regression coefficient. Addition of the second explanatory parameter, the acceptor number, is not statistically significant. This result is in agreement with the predominant role of Tl(I) ion solvation.

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Elektrochemische Untersuchungen von Tl(I)-Kronenetherkomplexen in nichtwäßrigen Medien

Zusammenfassung Es wurden die Komplexierungsgleichgewichte des Tl(I)-Ions mit 18-Krone-6 und Dibenzo-18-krone-6 polarographisch in 10 nichtwäßrigen Lösungsmitteln untersucht. Die Stabilität der Komplexe wird sehr stark vom Solvens beeinflußt, wobei eine starke Abhängigkeit von der Lewis-Basizität beobachtet wird. Es wurde festgestellt, daß die logK _s-Werte (K _s ist die Komplexstabilitätskonstante) gut mit der empirischen Beziehung logK _s=a DN+b beschrieben werden können, wobeiDN die Gutmann'sche Donorzahl unda undb die Regressionskonstanten bedeuten. Hinzunahme der Akzeptorzahl als zweiten Parameter bleibt statistisch insignifikant. Dieses Ergebnis stimmt mit dem dominierenden Einfluß der Tl(I)-Ionensolvatation überein.