Mutual interactions between nonionic surfactants and gelatin — investigations in cubic liquid crystalline systems and micellar systems

The mutual interactions between nonionic surfactants such as polyoxyethylene cetyl ethers (C₁₆EO _n ,n=15, 20) especially their cubic lyotropic liquid crystalline phases of typeI ₁ and polymer gelatin were investigated. The colloidal microstructure of such anI ₁-phase consisting of close-packed globular surfactant aggregates was shown by transmission electron microscopy (TEM). The diameter of the globules found by TEM correlated well with the periodic distance of about 7.5 nm obtained by small angle x-ray diffraction (SAXD). In ternary systems consisting of surfactant, gelatin, and water cubic liquid crystalline structures were also proved by polarized light microscopy, TEM, and SAXD. The polymer did not participate in the cubic structure but formed, at least in part, anisotropic spherulites. In diluted surfactant systems however, interactions between polymer and surfactants were clearly found by polarimetry. The nonionic surfactants caused an accelerated coil-helix transition of the polypeptid gelatin.     

无表面活性剂微乳液体系：N,N－二甲基甲酰胺/呋喃甲醛/水

通常微乳液一般由四个组分构成：水相、油相、表面活性剂和助表面活性剂。本文报道了一种不含表面活性剂的微乳液体系(简称SFME),由呋喃甲醛(油相),水和N,N－二甲基甲酰胺(DMF)三组分构成,不含传统的表面活性剂。对其相行为进行了研究,发现存在一个单相微乳液区和一个两相平衡区。采用电导率法和冷冻蚀刻电镜(FF-TEM)考察了单相区域中微乳液的微结构,结果表明可分为油包水(O/W)、双连续(BC)和水包油(W/O)三个区域。液滴直径介于40-70nm。     

Quantitative Characterization of Clay Dispersion in Polymer-Clay Nanocomposites

Summary: A novel methodology has been developed to describe the microstructure of polymer-clay nanocomposites quantitatively. It builds on the image analyses of transmission electron microscopy and optical microscopy micrographs, and two parameters, degree of dispersion and mean interparticle distance per unit volume of clay, are proposed to characterize the level of clay dispersion. It provides insights into the ‘real’ clay dispersion using a combination of both microscopical and macroscopical aspects.     

Use of reactive surfactants in basalt fiber reinforced polypropylene composites

Basalt fibers, similarly to other silicate fibers, can be introduced into both thermoplastic and thermosetting polymer matrices. In this work some basalt fiber reinforced polypropylene composites were investigated. The fiber-matrix adhesion was improved by commercial and non-commercial maleic anhydride derivatives. The latter types, called reactive surfactants, were prepared in laboratory scale and the progress of the syntheses was determined by Raman microscopy. The additives allowed performing reactive interface modification during the compounding process. Due to the interface modification with the additives in low concentration the mechanical properties improved. The boundary layers on the surface of the reinforcing fibers were observed using scanning electron microscopy (SEM).     

Preparation of micelle-encapsulated single-wall and multi-wall carbon nanotubes with amphiphilic hyperbranched polymer

The hyperbranched polyester (Boltorn^TM H20) was modified by maleic anhydride and then polystyrene (H20-MAh-PSt) to form amphiphilic micelles in water. The single-wall and multi-wall carbon nanotubes (SWCNTs and MWCNTs, respectively) were encapsulated in the formed micelles through non-covalent interactions. The formed structures were confirmed by FTIR, NMR, GPC, and XPS analysis. The dispersion and aggregation behaviors were observed by TEM and UV-vis and Raman spectroscopic analysis. The results showed that the dispersion performance of the obtained micelle-encapsulated carbon nanotubes in water was greatly improved compared to the pure carbon nanotubes. From the TEM observation, the individual SWCNT structure and the uniform polymer coating around the surface of SWCNT were seen after crosslinking. The Raman spectroscopic measurements also demonstrated that for the crosslinked samples, no effect occurred associated with concentration-dependent carbon nanotube aggregation.     

渣油加氢处理前后沥青质的微观结构研究

采用元素分析、扫描电镜和透射电镜等分析方法对渣油原料中的沥青质、加氢处理后的沥青质及添加高芳香性轻循环油(LCO)反应后的沥青质进行对比研究。结果发现,渣油加氢处理前后沥青质的表面呈现出光滑表面和多孔的球形颗粒表面两种完全不同的形貌。渣油加氢前后沥青质的芳核堆砌表现出明显的长程无序局部有序的特征;加氢处理后的沥青质芳核片层易于堆砌,出现了多层堆砌、长程有序的类石墨结构。渣油中高芳香性LCO的添加有利于促进沥青质的加氢反应、改善沥青质芳核系统在渣油加氢处理过程中的聚集行为。     

Effect of Processing Temperature on Gelation and Physical Properties of Low Density TEOS Based Silica Aerogels

In the present paper the experimental results of the effect of sol-gel processing temperature on the physical properties of the TEOS based silica aerogels are reported and discussed. The aerogels were produced by the two step sol-gel process at various temperatures in the range of 26–70^∘;C followed by supercritical drying using methanol solvent extraction. A remarkable reduction in the gelation time was observed from three and a half days at room temperature to a mere 18 hours at 50^∘;C. The best quality aerogels in terms of low density and high optical transmission were obtained for 6 hours hydrolysis time. The aerogels were characterized by the measurements of bulk density, volume shrinkage, porosity, refractive index and optical transmission. Monolithic aerogels with ultra low density (∼0.018 g/cm³), extremely high porosity (∼99%) and optimum optical transmission at 700 nm (∼75%) were obtained for the molar ratio of TEOS:MeOH:acidic water:basic water at 1:99:10.42:14.58 respectively.     

Comparative studies on molecular induced aggregation of hepta-imidazoliumyl-β-cyclodextrin towards anionic surfactants

A β-cyclodextrin derivative bearing seven cationic arms and its singly charged analogue, i.e., per-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin(3) and mono-6-deoxy-6-(1-methylimidazol-3-ium-3-yl)-β-cyclodextrin(4) were synthesized and fully characterized. Their induced aggregation behaviours towards two anionic surfactant, that is, sodium dodecyl sulfonate(SDS) and dioctyl sodium sulfosuccinate(Aerosol OT, AOT), were investigated by UV–vis, NMR, Zeta-potential, dynamic light scattering(DLS), and transmission electron microscopy. The results revealed that host 3 can induce the molecular aggregation of anionic surfactant at concentration far lower than its original CAC, leading to the larger diameter, the narrower size distribution and the higher thermal stability of the induced aggregate towards the anionic surfactant possessing more hydrophobic tails.     

Particle size measurements of heterogeneous film-forming latexes

Two-phase latex particles consisting of mainly polystyrene (PS) and polyisoprene (PI) in ratios varying from 7030 to 2080 were prepared using different polymerization techniques. Methacrylic acid (MAA) was used in small amounts as a comonomer. The latexes had narrow size distributions, and showed different particle morphologies depending on the monomer composition and the polymerization conditions used. In most cases the latexes were filmforming at room temperature. Particle size distributions and average particle sizes of the latexes have been determined using different particle sizing methods.Size determination by TEM was performed after staining with osmium tetroxide (OsO₄) or uranyl acetate (UAc). The staining methods showed no significant differences in particle size averages and particle size distributions when the ratio between the PI and PS phase did not exceed 5050. At higher phase ratios OsO₄ staining was preferred. The glass transition temperature of the PI phase increased after OsO₄ staining, which prevented deformation of the latex particles. Particle morphologies for the heterogeneous latex particles were also determined after OsO₄ staining.Particle sizes measured by TEM were generally smaller than the corresponding sizes measured by quasielastic light scattering (QELS). The difference in the measured diameters increased with increasing PI and PMAA content in the latex particles. The larger sizes observed by QELS are results of the presence of an immobilized water layer surrounding the particles in the aqueous environment, water absorption and swelling due to the presence of carboxylic acid groups, and adsorption of soluble carboxylated polymers forming a hydrophilic corona around the particles. By TEM the hard sphere diameters of dehydrated particles are measured.     

Determination of Sulfite in Botanical Medicine Using Headspace Thin-Film Microextraction and Surface Enhanced Raman Spectrometry

A facile method using headspace thin-film microextraction (HS-TFME) coupled with surface enhanced Raman spectrometry (SERS) has been developed for the determination of sulfite in traditional Chinese herbal medicine. The extraction substrate was synthesized by depositing urchin-like ZnO micron particles on glass sheets using chemical liquid phase deposition. Under the optimal conditions, the intensity of the SERS signal at 630–640?cm^?1 provided a good linear relationship with the concentration of sulfite from 25 to 400?mg/kg, and the linear correlation coefficient (R) was 0.996 with a detection limit of 6?mg/kg. The method was employed for the determination of sulfite in herbal medicines, and the results were confirmed by a traditional distillation-titration method. Therefore, this developed HS-TFME-SERS method may play an important role in the rapid, simple, and selective determination of sulfite residues in Chinese herbal medicine and become a potentially universal method for this analyte in various solid samples.     

吡啶-水体系中快速合成纳米Pt的新方法

在吡啶-水体系中用KBH4还原H2PtCl4首次制得了贵金属Pt纳米粒子且纳米Pt体系不受空气的影响可以较长时间的存在，并通过透射电镜(TEM)、低能电子衍射和紫外漫反射(UV-Vis)对其进行了表征．Pt纳米粒子的平均粒径在2．0～3．0nm，该体系同时也可以制备Ru、Pd等纳米粒子．     

Surface properties of fluorinated single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNTs) were fluorinated at several different temperatures. The change of atomic and electronic structures of fluorinated SWCNTs was investigated using X-ray photoelectron spectroscopy (XPS), electrical resistivity measurements and transmission electron microscopy (TEM). The amount of doped fluorine increases with increasing doping temperature, and the fluorine atoms are covalently attached to the side-wall of the SWCNTs. From Raman spectra and HRTEM study, the strong fluorination on the SWCNTs leads to the breaking of carbon–carbon bonds and the disintegration of tube structure. Several intermediate phases of fluorinated SWCNTs are observed during e-beam irradiation in HRTEM.     

Novel nonionic siloxane surfactants

A new method for ethoxylation without application of pressure is described. Butynediololigo(oxyethylene) [H(OCH₂CH₂)_n? OCH₂? C?C? CH₂O(CH₂CH₂O)_nH with n=1–16] has been prepared in the presence of an electrophilic catalyst in a specially developed reciruculating apparatus. The products have been characterized by NMR and IR spectroscopy. New nonionic silicone surfactants have been synthesized by hydrosilylation of these butynediololigo(oxyethylenes) with defined siloxanes and polysiloxanes. Protection of the hydroxyl group before hydrosilylation was not necessary. Hydrosilylation was carried out in the presence of a solvent. It has been possible to obtain surfactants with a surface tension of about 21-22 mN m^?1 and an interfacial tension of 2 mN m^?1.     

Imaging of Self‐Assembled Structures: Interpretation of TEM and Cryo‐TEM Images

The investigation of solution‐borne nanostructures by transmission electron microscopy (TEM) is a frequently used analytical method in materials chemistry. In many cases, the preparation of the TEM sample involves drying and staining steps, and the collection of images leads to the interaction of the specimen with the electron beam. Both aspects call for cautious interpretation of the resulting electron micrographs. Alternatively, a near‐native solvated state can be preserved by cryogenic vitrification and subsequent imaging by low‐dose cryogenic TEM. In this Minireview, we provide a critical analysis of sample preparation, and more importantly, of the acquisition and interpretation of electron micrographs. This overview should provide a framework for the application of (cryo)‐TEM as a powerful and reliable tool for the analysis of colloidal and self‐assembled structures with nanoscopic dimensions.     

Poly(methyl methacrylate)/silica/titania ternary nanocomposites with greatly improved thermal and ultraviolet-shielding properties

Poly(methyl methacrylate) (PMMA)/silica/titania ternary nanocomposites with covalent bonding interaction between polymer and inorganic phases have been prepared using a novel non-hydrolytic sol-gel method. Transmission electron microscope (TEM) image of silica/titania binary inorganic component indicates a core-shell-like structure. Scanning electron microscope (SEM) images suggest that the well dispersed silica/titania particles in the hybrid are on the nanometer-scale. The transparencies of nanocomposites are maintained in visible region while the absorption band in ultraviolet (UV) region is red shifted with increasing inorganic content. The thermogravimetric analysis (TGA) results show that the thermal stability of PMMA copolymer increases dramatically with the addition of silica/titania moieties both in nitrogen and in air.     

Characterization of nanomaterials in food by electron microscopy

Engineered nanomaterials (ENMs) are increasingly being used in the food industry. In order to assess the efficacy and the risks of these materials, it is essential to have access to methods that not only detect the nanomaterials, but also provide information on the characteristics of the materials (e.g., size and shape).This review presents an overview of electron microscopy (EM)-based methods that have been, or have the potential to be, applied to imaging ENMs in foodstuffs. We provide an overview of approaches to sample preparation, including drying, chemical treatment, fixation and cryogenic methods. We then describe standard and non-standard EM-based approaches that are available for imaging prepared samples. Finally, we present a strategy for selecting the most appropriate method for a particular foodstuff.     

Advanced TEM Characterization for Single-atom Catalysts: from Ex-situ Towards In-situ

Clean energy innovation has triggered the development of single-atom catalysts(SACs) due to their excellent catalytic activity, high tunability and low cost. The success of SACs for many catalytic reactions has opened a new field, where the fundamentals of catalytic property-structure relationship at atomic level await exploration, and thus raises challenges for structural characterization. Among the characterization techniques for SACs, aberration-corrected transmission electron microscopy(TEM) has become an essential tool for direct visualization of single atoms. In this review, we briefly summarize recent studies on SACs using advanced TEM. We first introduce TEM methods, which are particularly important for SACs characterization, and then discuss the applications of advanced TEM for SAC characterization, where not only atomic dispersion of single atoms can be studied, but also the distribution of elements and the valence state with local coordination can be resolved. We further extend our review towards in-situ TEM, which has increasing importance for the fundamental understanding of catalytic mechanism. Perspectives of TEM for SACs are finally discussed.     

Aggregation in dispersions of hematite and of hematite-akageneite composite containing anionic surfactants

The aggregation in dispersions of iron oxides was studied by dynamic light scattering and by TEM. In spite of high absolute value of zeta potential induced by specific adsorption of alkyl (C12–C16) sulfates, the particles showed substantial degree of aggregation. The particle size distributions observed in SDS-stabilized dispersions by dynamic light scattering were sensitive to the impurities contained in reagent-grade SDS. Namely, different specimens of reagent-grade SDS produced very different particle size distributions at otherwise identical experimental conditions.     

电子束敏感材料的原子尺度结构研究

分子筛和金属有机骨架(MOF)材料以其独特的孔道和骨架结构在催化、 储能、 干燥及净化和吸附分离等领域有着广泛应用, 对其结构的原子尺度表征对于深入理解其构效关系具有重要意义. 但其大孔道结构和有机骨架使得它们对电子束辐照极为敏感, 在常规透射电镜成像模式下结构会很快被破坏变为非晶, 从而无法获得孔道和骨架的原子排列信息. 最近发展起来的基于积分差分相位衬度扫描透射电子显微(iDPC-STEM)技术在电子敏感材料和轻元素组分成像方面展现出明显优势, 使得对多孔骨架材料及烃池物种的表征成为了可能. 本文综述了本课题组近期利用该技术对分子筛和MOF材料原子尺度结构方面的研究. 将iDPC-STEM技术应用到ZSM-5分子筛催化剂中, 实现了对该分子筛的原子级骨架结构的成像分析. 在MOF体系中, 利用该技术观察到MIL-101骨架内部有机连接体与金属节点的配位方式, 在此基础上解析了MIL-101结构中有机配体的连接和金属节点的苯环结构, 并观察了MOF的原子级表面、 界面和缺陷等局域结构特征. 最后对iDPC-STEM技术在原子尺度成像方面的应用潜力进行了总结与展望.