表面活性剂有序聚集体在纳米材料制备中的应用

介绍了表面活性剂在溶液中形成的各种有序聚集体－胶团（反胶团），微乳液，液晶及囊泡等，综述了它们作为微反应器或作为模板在纳米材料制备中的应用。     

Molecular recognition by wall-assembling-type nanocavity in aqueous media

Steroid cyclophanes, each having a macrocyclic ring attached to four bile acid moieties via chiral lysine connectors, were synthesized, and the binding of the 2-naphthylphenylketone (guest) to the steroid cyclophanes in water was investigated. The circular dichroism spectra of the steroid cyclophane with cholic acid and L-lysine were significantly affected by the binding of the guest, and the induced circular dichroism based on the absorption of the achiral guest was also observed. The binding of the guest to the steroid cyclophane with cholic acids and D-lysines induced changes in the circular dichroism spectra with the opposite sign of the molecular ellipticities. An induced circular dichroism spectral change was not observed upon binding of the guest to the analogous host without OH sites. These results strongly suggest that the guest is conformationally fixed through hydrogen bonding between the carbonyl group of the guest and the steroidal hydroxyl group of the host. The assembly of only four steroid residues on the macrocyclic ring probably provided a hydrophobic nanocavity for hydrogen bonding.     

Assemblies of biomaterials in mesoporous media

Assemblies of biomaterials onto mechanically stable inorganic structure are advantageous for the practical applications because of the potential to improve the stability and performance of biomaterials in the biocatalytic processes. Among many kinds of inorganic materials, mesoporous materials such as mesoporous silica and mesoporous carbon have attracted special attention owing to their well-defined structures and perfectly controlled pore geometries, which would lead to unique functions such as size selective adsorption of biomaterials. In the first part of this review, adsorption behaviors of proteins, enzymes, vitamins, and amino acids in aqueous solutions onto mesoporous media are systematically explained. Pore geometries (pore diameter and volume) of mesoporous materials are the crucial factors for the size selective adsorption of biomaterials, especially proteins, which often have a size comparable to pore dimension. The studies on the adsorption of biomaterials on the mesoporous carbon reveal that hydrophobic interaction between guest molecules and surface of the mesoporous materials is an important parameter which controls the amount of biomaterials adsorption. Enhanced adsorption of biomaterials was commonly observed at their isoelectric point, where electrostatic repulsion is minimized between the biomaterials. In addition, several functions such as biomolecular separation, reactor function, controlled drug release, and photochemical properties are discussed in the latter sections. Studies on assemblies of biomaterials in mesoporous media are still in initial stage, but the development of appropriately designed mesoporous materials would powerfully promote researches in these fascinating unexplored fields.     

Solvation structure,hydrogen bonding,and ion pairing in dilute supercritical aqueous NaCl mixtures

We review molecular dynamics simulations of infinitely dilute supercritical aqueous NaCl solutions to determine the solvation structure and the soluteinduced effect on water water hydrogen bonding and report new simulation results On the extent of the ion pairing. Our simulation studies indicate that Na⁺ and Cl ions as a pair or its isolated infinitely dilute ions form strong solvation structures in SCW. even though the water eater hydrogen bonding is not affected Within the context of the models we are using. there is strong indication of a high degree of Na⁺ CI ion pairing.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado. U.S.A.     

Chemical Information Exchange in Organized Protocells and Natural Cell Assemblies with Controllable Spatial Positions

An ultrasound‐based platform is established to prepare homogenous arrays of giant unilamellar vesicles (GUVs) or red blood cell (RBCs), or hybrid assemblies of GUV/RBCs. Due to different responses to the modulation of the acoustic standing wave pressure field between the GUVs and RBCs, various types of protocell/natural cell hybrid assemblies are prepared with the ability to undergo reversible dynamic reconfigurations from vertical to horizontal alignments, or from 1D to 2D arrangements. A two‐step enzymatic cascade reaction between transmitter glucose oxidase‐containing GUVs and peroxidase‐active receiver RBCs is used to implement chemical signal transduction in the different hybrid micro‐arrays. Taken together, the obtained results suggest that the ultrasound‐based micro‐array technology can be used as an alternative platform to explore chemical communication pathways between protocells and natural cells, providing new opportunities for bottom‐up synthetic biology.     

Nature of hydrogen bonding of water molecules in aqueous solutions of glycerol by attenuated total reflection (ATR) infrared spectroscopy

Attenuated total reflection infrared (ATR-IR) spectroscopy was performed on glycerol/water solutions in order to gain a better understanding of the strong hydrogen bonding of glycerol as a humectant. The OH stretching band after eliminating the contribution of glycerol OH in the glycerol/water solutions was decomposed using three Gaussian components. With increasing glycerol concentrations up to 50 volume %, the decrease of the 3428 cm(-1) component (middle H-bond component) and the increase of the 3562 cm(-1) component (longer H-bond component) suggested the breaking of H bonds among water molecules. On the other hand, the 3242 cm(-1) component (shorter H-bond component) remained unchanged. It was expected that water molecules surrounding glycerol molecules are retained by strong H bonding between H atoms of water and O atoms in C-O of glycerol when aqueous solutions containing glycerol are introduced in human skin.     

Application of polyaniline/manganese dioxide composites for degradation of acid blue 25 by hydrogen peroxide in aqueous media

The kinetics of catalytic degradation of acid blue 25 dye (AB-25) by hydrogen peroxide using polyaniline/manganese dioxide (PANI/MnO₂) composites was investigated. To optimize the degradation kinetics of the dye, several parameters have been varied: (i) parameters varied during the preparation of PANI/MnO₂ composites include: aniline concentration, acid concentration, acid type, amount of ??-MnO₂, stirring time and polymerization temperature and (ii) kinetic variables include: [H₂O₂], dye concentration, amount of composite, pH, addition of salt, and UV-light irradiation. The catalytic activity of the composite is obtained when it has (i) high % PANI content, (ii) high degree of crystallinity, and (iii) high doping ratio. The reaction obeyed second-order kinetics with respect to [H₂O₂], attains a maximum, and decreases thereafter. The degradation decreased when the dye concentration increased. Additionally, the effect of salts on the degradation rate was also studied. The rate of reaction decreases with increasing pH of the medium due to (i) the conversion of ES form of PANI into EB form and (ii) protonated form of the dye is more facial to be oxidized than the deprotonated form. Degradation rate was increased in the presence of UV/H₂O₂ compared to H₂O₂ alone. Mechanism was proposed for the catalytic degradation reaction which is in agreement with the experimental data.     

From liquid to solid bonding in cohesive granular media

We study the transition of a granular packing from liquid to solid bonding in the course of drying. The particles are initially wetted by a liquid brine and the cohesion of the packing is ensured by capillary forces, but the crystallization of the solute transforms the liquid bonds into partially cemented bonds. This transition is evidenced experimentally by measuring the compressive strength of the samples at regular intervals of times. Our experimental data reveal three regimes: (1) Up to a critical degree of saturation, no solid bonds are formed and the cohesion remains practically constant; (2) The onset of cementation occurs at the surface and a front spreads towards the center of the sample with a nonlinear increase of the cohesion; (3) All bonds are partially cemented when the cementation front reaches the center of the sample, but the cohesion increases rapidly due to the strengthening of cemented bonds. We introduce a model based on a parametric cohesion law at the bonds and a bond crystallization parameter. This model predicts correctly the phase transition and the relation between microscopic and macroscopic cohesion.     

有序分子薄膜结构的X射线光电子能谱表征

有序分子薄膜由于其特殊的结构而表现出优异的性能。为此,人们对微结构与宏观性能之间的关系极为重视。本文重点讨论了近年来X射线光电子能谱在有序分子薄膜位结构分析中取得的结果及其应用情况。其中包括薄膜厚度的确定、薄膜-基底界面结构、分子之间的相互作用情况及其有序分子结构对薄膜电学、气体敏感特性等宏观性能的影响。研究结果说明,X射线光电子能谱由于其对薄膜的损伤小、表面探测灵敏度高和较高的能量分辨能力,因此是确定有序分子薄膜微结构的重要手段之一。     

盐水介质中分散聚合法制备两性聚电解质的研究

利用聚丙烯酰氧乙基三甲基氯化铵(PDAC)作为分散稳定剂,阴离子单体丙烯酸(从)、阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)和非离子单体丙烯酰胺(AM)在硫酸铵水溶液中通过分散共聚合,制备了稳定分散在盐水中的聚合物微球.考察了无机盐浓度、分散剂用量对分散共聚合的影响.研究结果表明:体系内无机盐浓度的增加导致聚合物分子量降低;而随分散剂浓度的增加,微球粒径先减小后增加.制备的两性聚电解质溶液在等电点附近时,聚合物的特性黏度随盐浓度的增加而增加,显示明显的反聚电解质效应.     

Influence of hydrogen bonding on properties of BIS-GMA analogues

The influence of chemical structure on the important properties of composite matrix resins is being systematically investigated. This study addresses the relationships between pendent side chain structures, viscosity and curing shrinkage. In particular, viscosity is known to be greatly influenced by intermolecular interactions, such as hydrogen bonding, and free volume effects. In order to establish the relative importance of these factors, analogues of BIS-GMA were synthesized in which the pendent hydroxyl groups were replaced by trimethyl siloxyl, and by dimethyl, isopropyl siloxyl groups. The viscosities were determined with a cone and plate viscometer and curing shrinkages were determined gravimetrically. They were compared to previously determined values for BIS-GMA and its methyl and hydrogen substituted analogues. The high viscosity of BIS-GMA is drastically reduced by replacement of the hydroxyl group, or its substitution by silylation. The relatively smaller effects produced by varying the bulk of the substituted side chains indicates that the main effect on viscosity is due to the presence or absence of hydrogen bonding. Conversely, increasing the bulk of the side chain substituent has less effect on viscosity, but significantly reduces the curing shrinkage. Changes in curing shrinkages were explained in terms of effects of free volumes associated with the monomers.     

Examination of processes of hydrogen absorption in corrosion of steels in hydrogen sulfide-containing media

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 3, pp. 44–50, May–June, 1992.     

CZTS synthesis in aqueous media by microwave irradiation

Copper zinc tin sulfide (Cu₂ZnSnS₄, CZTS), a p-type semiconductor composed of non-toxic earth abundant elements, is a promising material for absorber layer application in thin film solar photovoltaics. The present work describes a relatively faster and reliable microwave irradiation technique to prepare CZTS powder in aqueous media. The CZTS phase of the as-synthesized powder was confirmed by X-ray diffraction and Raman spectroscopy. Optical properties i.e. band gap determined from Tauc plot of the optical absorption spectrum measured by UV–Vis spectroscopy was 1.27 eV, which is suitable for absorbing the solar radiation. The particle morphology studied under SEM and TEM analysis was found to be a 3D flower-like nanostructure formed from 2D layers of CZTS crystals. Further, the most probable mechanism for the formation of CZTS phase is explained.     

Investigation of aqueous stability of taxol in different release media

In the present study, the aqueous stability of taxol in different aqueous media and immiscible aqueous/organic systems at 37?°C was investigated. The aqueous media included phosphate buffered saline (PBS) and PBS containing 10% methanol, 10% ethanol, 10% hydroxypropyl β-cyclodextrin (HP-βCD), 1% sodium citrate and 1% Tween 80. The immiscible systems consisted of PBS/octanol, PBS/dichloromethane, PBS/chloroform and PBS/ethyl acetate. The concentrations of taxol and related derivatives in each of the media were determined through the high-performance liquid chromatography assay. Results showed that hydrolysis and epimerization were two major types of degradation for taxol in the aqueous media starting from the initial hours of contact (6 hours). Addition of Tween 80 to PBS moderately increased the aqueous stability of taxol. As well, using PBS containing 10% HP-βCD inhibited the taxol hydrolysis, while epimerization still in process. In the case of immiscible systems, except for PBS/ethyl acetate system, no evidences of taxol hydrolysis were observed. Meanwhile, epimerization of taxol in PBS/dichloromethane and PBS/chloroform systems underwent due to the ability of C–Cl bonds to form hydrogen bonding with the hydroxyl group of C7 of taxol.