界面光化学反应研究进展

本文介绍了在气液界面上和LB 膜中的光化学反应特点及不同的类型, 从界面光聚合、界面光致变色、界面光致电子转移、光电转化等几个方面对最近几年来在界面光化学领域内的重要成果及最新进展进行了综述, 并对这一领域的发展和应用前景进行了展望。     

氯仿,乙醇,苯有关二元体系加压相平衡研究

氯仿、乙醇、苯有关二元体系加压相平衡研究马忠明，陈庚华，王琦，严新焕，韩世钧，余淑娴（浙江大学化学系，杭州，３１００２７）（江西大学化学系）关键词加压汽液平衡，醇烃体系，氯仿，乙醇，苯醇是极性分子，烃是非极性或弱极性分子，醇与醇、烃与烃分子及醇与烃分...     

两种不同光谱类型的R-藻红蛋白的荧光性质研究

红藻中的R-藻红蛋白(R-PE)依照其吸收光谱可分为两种不同的光谱类型,即“双峰型”和“三峰型”。本文通过对不同pH条件下的R-PE的荧光光谱及荧光寿命的研究,发现“三峰型”R-PE的pH稳定范围较“双峰型”R-PE大。在R-PE浓度对荧光光谱的影响实验中,随着蛋白浓度的增加,荧光峰位置逐渐红移。荧光寿命逐渐增大,荧光强度先行增加而后减弱。用碘离子对其荧光进行猝灭,随着碘离子浓度的增大,荧光强度逐渐降低,荧光寿命逐渐缩短,并服从Stem-Volmer规则。     

Dynamic Visualization of Free Radicals at Single Oxygen Bubbles using Chemiluminescence

The generation of free radicals is a key process in the formation and the collapse of the bubbles in water, however, the direct and dynamic observation of the radicals in this process at single bubbles has never been achieved. Here, the hydroxyl (OH^.) and oxygen (O₂^.−) radicals at single oxygen bubbles are continuously traced using chemiluminescence (CL), in which these radicals at the bubble react with the surrounding luminol in the solution emitting the light. Varied increase trends of luminescence are observed in the generation of a bubble, floating, short parking at the water/air interface and the final explosion, revealing the complexity in the distribution of radicals at the bubble unprecedentedly. Despite more radicals are observed at the bubble generated at a deep position under the water for the stabilization, almost the same amount of radicals are included in the bubbles that is independent on the water pressure during the production of the bubble. This rich information collected from the dynamic study of bubbles illustrates the complicated generation and distribution process of radicals at the bubbles, and will facilitate the understanding of the function about the bubbles.     

Rheology of hydrophobically modified polyacrylamide-co-poly(acrylic acid) on addition of surfactant and variation of solution pH

Constant shear and shear dependent viscosity measurements are reported in aqueous systems of co- and terpolymers of acrylamide (AM), N-n-alkylacrylamide (C10, C12, and C14 alkyl groups), and acrylic acid (AA) with added anionic surfactant sodium dodecyl sulfate (SDS). The results are presented as three-dimensional plots of viscosity vs surfactant concentration and pH at constant shear rate or viscosity vs shear rate and surfactant concentration at constant pH. For terpolymers incorporating AA, a strong viscosity maximum is observed at intermediate pH values (pH 4-6) where the AA groups are partially ionized and at SDS concentrations close to the critical micelle concentration. At high pH, all AA incorporating terpolymer solutions with SDS are strongly shear thinning, but at pH 3-4 the systems of terpolymers with SDS are strongly shear thickening at low shear, followed by a shear-thinning region at high shear. These results are explained in terms of surfactant-mediated network formation with polymer coil expansion and hydrogen bonding between partially ionized AA groups as additional factors.     

4H-Thiopyran-1-oxides. Conformational analysis and photochemical isomerization

The stereochemical aspects and photochemistry of a series of 2,4,4,6-tetrasubstituted-4H-thiopyran-1-oxides are described. Substitution-induced changes to the sulfinyl group stereomutation and the ring conformation are investigated. The sulfoxides were configurationally stable at a wide thermal range, but underwent photocatalysed stereomutation at sulfur without concomitant isomerization at C-4. In almost all cases the trans isomer predominated at equilibrium. The theoretical studies are in close agreement with experimental results.     

5%Al-Zn-0.1%RE合金非晶带的研究

用急冷法制取５％Ａｌ－Ｚｎ－０．１％ＲＥ合金薄带,通过Ｘ射线衍射,差式量热扫描和高分辨透射电子显微镜观察表明,这种合金薄带为纳米晶粒弥散的非晶合金。对不同冷却速度得到的合金薄带进行观察比较,发现冷却速度越快得到的合金晶粒越差,在低冷却速度下反而容易获得室温下稳定的纳米晶粒弥散的非晶合金,而且晶粒细化。     

用磷酸盐预处理制备PAN基活性中空炭纤维

用不同浓度的(NH4)2HPO4溶液和不同浸渍时间处理过的聚丙烯腈(PAN)基中空纤维在空气中270℃预氧化，并在N2气氛下于700℃炭化，随后用CO2气体在800℃活化，测定了PAN基活性中空炭纤维对肌酐、VB12和胆红素的吸附量．考察了(NH4)2HPO4的浓度和浸渍时间对PAN基活性中空炭纤维性能的影响．通过（NH4)2HPO4的预处理可以有效地提高PAN基活性中空炭纤维的活化收率，改善PAN基活性中空炭纤维的吸附性能．     

Radiolysis of poly(vinyl chloride)

Allyl free-radical intermediates are detected by ultraviolet absorption at 255 mu in poly(vinyl chloride) irradiated at ?196°C and stored at 25°C. In vacuum at 25°C, allyl radicals are converted into polyenyl free radicals and polyenes. From the nature of allyl radical decay in vacuum, radical chain transfer between polyenyl radicals and poly(vinyl chloride) is inferred. Allyl and polyenyl free radicals are scavenged by oxygen on post-irradiation storage in air.     

Solvent dynamics following charge transfer at the liquid-liquid interface

The dynamics of solvent reorganization following charge transfer at the interface between two immiscible liquids, one polar and the other non-polar are investigated by molecular dynamics. Both charge separation and charge recombination processes in two different orientations at the surface are considered and are compared with the same processes in the bulk polar solvent. The relaxation at the surface is significantly slower than in the bulk, in contrast to predictions of continuum models. The linear response approximation works reasonably well in the bulk but fails at the interface. The Langevin model is in poor agreement with the exact equilibrium correlations, especially at short time, but can qualitatively account for the overall rate.     

Vibrational spectroscopy of ferruginous smectite and nontronite

A comparison is made between the Raman and infrared spectra of ferruginous smectite and a nontronite using both absorption and emission techniques. Raman spectra show hydroxyl stretching bands at 3572, 3434, 3362, 3220 and 3102 cm(-1). The infrared emission spectra of the hydroxyl stretching region are significantly different to the absorption spectrum. These differences are attributed to the loss of water, absent in the emission spectrum, the reduction of the samples in the spectrometer and possible phase changes. Dehydroxylation of the two minerals may be followed by the loss of intensity of the hydroxyl stretching and hydroxyl deformation frequencies. Hydroxyl deformation modes are observed at 873 and 801 cm(-1) for the ferruginous smectite, and at 776 and 792 cm(-1) for the nontronite. Raman hydroxyl deformation vibrations are found at 879 cm(-1). Other Raman bands are observed at 1092 and 1032 cm(-1), assigned to the SiO stretching vibrations, at 675 and 587 cm(-1), assigned to the hydroxyl translation vibrations, at 487 and 450 cm(-1), attributed to OSiO bending type vibrations, and at 363, 287 and 239 cm(-1). The differences in the molecular structure of the two minerals are attributed to the Al/Fe ratio in the minerals.     

A Raman spectroscopic study of synthetic giniite

The mineral giniite has been synthesised and characterised by XRD, SEM and Raman and infrared spectroscopy. SEM images of the olive-green giniite display a very unusual image of pseudo-spheres with roughened surfaces of around 1-10microm in size. The face to face contact of the spheres suggests that the spheres are colloidal and carry a surface charge. Raman spectroscopy proves the (PO4)3- units are reduced in symmetry and in all probability more than one type of phosphate unit is found in the structure. Raman bands at 77K are observed at 3380 and 3186cm-1 with an additional sharp band at 3100cm-1. The first two bands are assigned to water stretching vibrations and the latter to an OH stretching band. Intense Raman bands observed at 396, 346 and 234cm-1are attributed to the FeO stretching vibrations. The giniite phosphate units are characterised by two Raman bands at 1023 and 948cm-1 assigned to symmetric stretching mode of the (PO4)3- units. A complex band is observed at 460.5cm-1 with additional components at 486.8 and 445.7cm-1 attributed to the nu(2) bending modes suggesting a reduction of symmetry of the (PO4)3- units.     

The isomerization of cycloheptatriene at high temperatures

The isomerization of cycloheptatriene at high temperatures (800–1250°K) has been studied experimentally using a shock tube at high pressures and by very low-pressure pyrolysis in the intermediate-pressure region (the first direct use of the latter technique for an isomerization). Rate coefficients obtained are in accord with previous results at lower temperatures. The results are examined theoretically to account for weak-collision nonequilibrium effects. These corrections are found to be appreciable at the temperatures studied.     

TEMPERATURE DEPENDENCE OF THE PHOSPHORESCENCE LIFETIMES OF HETEROGENEOUS TRYPTOPHAN RESIDUES IN GLOBULAR PROTEINS BETWEEN 293 AND 77 K

Abstract— The phosphorescence of five globular proteins containing tryptophan residues was observed in deoxygenated neutral ethylene glycol-phosphate buffer (1:1 by volume) at 293 and 77 K. Their spectral features at 293 K are closely identical to those at 77 K apart from a lack of tyrosine phosphorescence at 293 K. and are independent of the excitation wavelength between 250 and 310 nm. From the present results. it can be concluded that the buried tryptophan residues are the only phosphorescing centers at room temperature. Their phosphorescence lifetimes were measured as a function of temperature in the range from 77 to 293 K. At room temperature, their phosphorescence lifetimes are between about 1 and 500 ms. On the basis of their temperature dependence, the heterogeneous tryptophan environments are discussed in terms of a temperature-activated nonradiative rate. We suggest that the observation of the phosphorescence characteristics of globular proteins containing tryptophan residues buried in the interior of the protein molecule at room temperature is likely to prove useful in probing the protein structure in solution.     

Unexpected shielding of methyl group protons in some piperidines

High resolution 1H and 13C NMR spectra of four 3-ethyl-4-hydroxy- 4-phenylpiperidines 1-4 have been recorded in CDCl3 and analysed. The conformations of phenyl and hydroxyl groups at C(4) and ethyl group at C(3) were analysed in detail. The chemical shift of the methyl protons in the ethyl group are quite surprising; they are close to TMS in CDCl(3) and even negative in DMSO-d6. These results are interpreted in terms of the magnetic anisotropy of the phenyl rings at C(2) and C(4) which, in turn, depend on the conformations of the ethyl group at C(3) and the hydroxyl group at C(4). Favoured conformations of ethyl group at C(3) and hydroxyl group at C(4) were calculated by AM1 methods.     

Inorganic complexation of nickel and cobalt in natural waters

The distribution of nickel and cobalt species has been computed, based on the pH-dependent model of Zirino and Yamamoto. The media used in the pH range of 7 to 9 are natural waters like fresh water, sea water and a mixture of them at different compositions, at 25°C temperature and 1 atm pressure. In fresh water, both nickel and cobalt dominate as free cations at lower pH, and as carbonato complexes at higher pH. In sea water, chloro complexes are significant. In mixtures of the two kinds of water, as might be found in a totally mixed estuary, chloro complexes are important, varying slowly with pH. Sea water plays an important role in complexation. The present results are in excellent agreement with experimental data obtained by the resin exchange method.     

Microwave enhanced electroanalysis of formulations: processes in micellar media at glassy carbon and at platinum electrodes

The direct electroanalysis of complex formulations containing alpha-tocopherol (vitamin E) is possible in micellar solution and employing microwave-enhanced voltammetry. In the presence of microwave radiation substantial heating and current enhancement effects have been observed at 330 microm diameter glassy carbon electrodes placed into a micellar aqueous solution and both hydrophilic and highly hydrophobic redox systems are detected. For the water soluble Fe(CN)(6)(3-/4-) redox system in micellar aqueous solutions of 0.1 M NaCl and 0.1 M sodium dodecylsulfate (SDS) at low to intermediate microwave power, thermal effects and convection effects are observed. At higher microwave power, thermal cavitation is induced and dominates the mass transport at the electrode surface. For the micelle-soluble redox systems tert-butylferrocene and 2,5-di-tert-butyl-1,4-benzoquinone, strong and concentration dependent current responses are observed only in the presence of microwave radiation. For the oxidation of micelle-soluble alpha-tocopherol current responses at glassy carbon electrodes are affected by adsorption and desorption processes whereas at platinum electrodes, analytical limiting currents are obtained over a wide range of alpha-tocopherol concentrations. However, for the determination of alpha-tocopherol in a commercial formulation interference from proteins is observed at platinum electrodes and direct measurements are possible only over a limited concentration range and at glassy carbon electrodes.     

Spatial desynchronization of glycolytic waves as revealed by Karhunen-Loeve analysis

The dynamics of glycolytic waves in a yeast extract have been investigated in an open spatial reactor. At low protein contents in the extract, we find a transition from inwardly moving target patterns at the beginning of the experiment to outwardly moving spiral- or circular-shaped waves at later stages. These two phases are separated by a transition phase of more complex spatiotemporal dynamics. We have analyzed the pattern dynamics in these three intervals at different spatial scales by means of a Karhunen-Loeve (KL) decomposition. During the initial phase of the experiment, the observed patterns are sufficiently described by the two dominant KL modes independently of the spatial scale. However, during the last stage of the experiment, at least 6 KL modes are needed to account for the observed patterns at spatial scales larger than 3 mm, while for smaller scales, 2 KL modes are still sufficient. This indicates that in the course of the experiment, the local glycolytic oscillators become desynchronized at spatial scales larger than 3 mm. Possible reasons for the desynchronization of the glycolytic waves are discussed.