磁场中电解质内胶态粒子的电荷分布

为了探求磁处理技术防垢的机理，应用电学与统计力学的理论和数学分析的方法。对电解质内胶态粒子周围的电荷分布进行了研究，计算了磁场对这种电荷分布的影响，给出了在温度较高及稀溶液情况下磁场对胶态粒子周围电荷分布影响的公式。认为电解质内的胶态粒子周围带有一层离子电荷，其厚度取决于温度与离子的浓度。当离子浓度离子大时，离子层变薄，促使胶粒之间发生凝聚；当温度增高时，离子层变厚，阻碍胶粒之间发生凝聚。当电解质     

Field-Induced Layering of Colloidal Crystals

An electrohydrodynamic methodology has been developed that makes possible the precise assembly of two- and three-dimensional colloidal crystals on electrode surfaces. Electrophoretically deposited colloidal particles were observed to move toward one another over very large distances (greater than five particle diameters) to form two-dimensional colloidal crystals for both micrometer- and nanometer-size particles. This coalescence of particles with the same charge is opposite to what is expected from electrostatic considerations and appears to result from electrohydrodynamic fluid flow arising from an ionic current flowing through the solution. The ability to modulate this "lateral attraction" between particles, by adjusting field strength or frequency, facilitates the reversible formation of two-dimensional fluid and crystalline colloidal states on the electrode surface. Further manipulation allows controlled structures to be assembled.     

Aldrin: removal from lake water by flocculent bacteria

Floc-forming bacteria isolated from Lake Erie adsorb and concentrate aldrin from colloidal dispersion so that the settling of the bacterial flocs removes aldrin from the water phase. Contemporary sediments forming in Lake Erie contain aldrin and could adsorb more. The sediments consist of a conglomerate floc of bacteria, diatoms, and inorganic and detrital particles. Flocculent bacteria also adsorb microparticulates, and this adsorption capacity represents a mechanism for sediment formation and for the removal of suspended particles including aldrin from the water column.     

Surfactant-mediated two-dimensional crystallization of colloidal crystals

Colloidal particles can form unexpected two-dimensional ordered colloidal crystals when they interact with surfactants of the opposite charge. Coulomb interactions lead to self-limited adsorption of the particles on the surface of vesicles formed by the surfactants. The adsorbed particles form ordered but fluid rafts on the vesicle surfaces, and these ultimately form robust two-dimensional crystals. This use of attractive Coulomb interaction between colloidal particles and surfactant structures offers a potential new route to self-assembly of ordered colloidal structures.     

猪瘟胶体金快速诊断试纸条的研制

采用柠檬酸钠还原法制备胶体颗粒,用猪瘟(CSF)抗体标记纯化,并包被在玻璃纤维膜上,另外将纯化的CSF抗体和羊抗鼠抗体包被在硝酸纤维膜上,组装成CSF快速检测条,对猪瘟病毒进行检测.结果表明:使用所研制的CSF快速检测条检测收集的70份待检样品,共检出猪瘟阳性病例26例,而经病毒分离鉴定阳性病例有28例,阳性符合率达92.8%;将5份阳性猪瘟病毒稀释后用试纸条和ELISA方法进行敏感性实验,结果表明,诊断试纸条的敏感性较高,用试纸条对鸽新城疫病毒、鸡减蛋综合症病毒、猪传染性胃肠炎病毒、猪繁殖与呼吸障碍综合症病毒进行检测,无交叉反应.     

A class of microstructured particles through colloidal crystallization

Microstructured particles were synthesized by growing colloidal crystals in aqueous droplets suspended on fluorinated oil. The droplets template highly ordered and smooth particle assemblies, which diffract light and have remarkable structural stability. The method allows control of particle size and shape from spheres through ellipsoids to toroids by varying the droplet composition. Cocrystallization in colloidal mixtures yields anisotropic particles of organic and inorganic materials that can, for example, be oriented and turned over by magnetic fields. The results open the way to controllable formation of a wide variety of microstructures.     

Three-dimensional direct imaging of structural relaxation near the colloidal glass transition

Confocal microscopy was used to directly observe three-dimensional dynamics of particles in colloidal supercooled fluids and colloidal glasses. The fastest particles moved cooperatively; connected clusters of these mobile particles could be identified; and the cluster size distribution, structure, and dynamics were investigated. The characteristic cluster size grew markedly in the supercooled fluid as the glass transition was approached, in agreement with computer simulations; at the glass transition, however, there was a sudden drop in their size. The clusters of fast-moving particles were largest near the alpha-relaxation time scale for supercooled colloidal fluids, but were also present, albeit with a markedly different nature, at shorter beta-relaxation time scales, in both supercooled fluid and glass colloidal phases.     

Novel Colloidal Interactions in Anisotropic Fluids

Small water droplets dispersed in a nematic liquid crystal exhibit a novel class of colloidal interactions, arising from the orientational elastic energy of the anisotropic host fluid. These interactions include a short-range repulsion and a long-range dipolar attraction, and they lead to the formation of anisotropic chainlike structures by the colloidal particles. The repulsive interaction can lead to novel mechanisms for colloid stabilization.     

Colloid formation during waste form reaction: implications for nuclear waste disposal

Insoluble plutonium- and americium-bearing colloidal particles formed during simulated weathering of a high-level nuclear waste glass. Nearly 100 percent of the total plutonium and americium in test ground water was concentrated in these submicrometer particles. These results indicate that models of actinide mobility and repository integrity, which assume complete solubility of actinides in ground water, underestimate the potential for radionuclide release into the environment. A colloid-trapping mechanism may be necessary for a waste repository to meet long-term performance specifications.     

Structure of solidified colloidal array laser filters studied by cryogenic transmission electron microscopy

Ordered arrays of charged uniform colloidal polystyrene particles in solution form a single-wavelength laser filter that is transparent to other wavelengths. A usable filter was prepared by solidification within an acrylamide-methylene-bisacrylamide gel. The rejection wavelength of the colloidal array filter changes with gel composition. Cryogenic transmission electron microscopy of two gel formulations shows that the colloidal array filter is composed of AAA stacking of close-packed planes. Excellent agreement is found between the layer spacings measured and those predicted from the rejection wavelengths.     

Colloidal jamming at interfaces: a route to fluid-bicontinuous gels

Colloidal particles or nanoparticles, with equal affinity for two fluids, are known to adsorb irreversibly to the fluid-fluid interface. We present large-scale computer simulations of the demixing of a binary solvent containing such particles. The newly formed interface sequesters the colloidal particles; as the interface coarsens, the particles are forced into close contact by interfacial tension. Coarsening is markedly curtailed, and the jammed colloidal layer seemingly enters a glassy state, creating a multiply connected, solidlike film in three dimensions. The resulting gel contains percolating domains of both fluids, with possible uses as, for example, a microreaction medium.     

Two-dimensional nematic colloidal crystals self-assembled by topological defects

The ability to generate regular spatial arrangements of particles is an important technological and fundamental aspect of colloidal science. We showed that colloidal particles confined to a few-micrometer-thick layer of a nematic liquid crystal form two-dimensional crystal structures that are bound by topological defects. Two basic crystalline structures were observed, depending on the ordering of the liquid crystal around the particle. Colloids inducing quadrupolar order crystallize into weakly bound two-dimensional ordered structure, where the particle interaction is mediated by the sharing of localized topological defects. Colloids inducing dipolar order are strongly bound into antiferroelectric-like two-dimensional crystallites of dipolar colloidal chains. Self-assembly by topological defects could be applied to other systems with similar symmetry.     

A lost-wax approach to monodisperse colloids and their crystals

We report a nanoscale "lost-wax" method for forming colloids with size distributions around 5% and their corresponding colloidal crystals. Macroporous polymer templates are first prepared from a silica colloidal crystal. We then use the uniform and interconnected voids of the porous polymer to generate a wide variety of highly monodisperse inorganic, polymeric, and metallic solid and core-shell colloids, as well as hollow colloids with controllable shell thickness, as colloidal crystals. We can also uniformly deform the polymer template to alter colloidal shape and demonstrate the formation of elliptical particles with precisely controlled aspect ratios.     

O型口蹄疫单克隆抗体6H4株金标试纸条的制备

以制备的O型口蹄疫单克隆抗体为基础,结合免疫金技术,采用柠檬酸三钠还原法制备胶体金颗粒,对6H4单克隆抗体进行标记,制备了该单克隆抗体的金标试纸条.研究结果表明,6H4单克隆抗体在pH 8.64下的稳定点为12 mg/L,可制备成金标记抗体及其反应膜.     

改性含蜡原油剪切效应机理研究的思考

在长距离管道输送过程中,剪切作用会恶化因加剂处理而得到改善的原油流变性.要解决加剂原油的剪切稳定性问题,就必须在有关机理研究上取得突破.在总结国内外研究现状的基础上,从分子问作用力、胶粒间作用力和原油流变学研究三个方面,分析了目前研究中普遍存在的基础研究薄弱、试验影响因素多、条件性试验方法不统一等问题,提出了加强基础理论研究、不局限于当前的研究结论、运用多种方法开展综合研究的建议.     

Hematite nanospheres of possible colloidal origin from a precambrian banded iron formation

Exceptionally small spheres (nanospheres) of hematite (diameters between 120 and 200 nanometers) occur in the Marra Mamba Iron Formation of the Hamersley Basin, Australia. The nanospheres are clustered into small aggregates and may have formed by structural ordering and dehydration of colloidal iron hydroxide particles. Individual spheres consist of numerous thin, curved hematite platelets surrounding a central void that is approximately half the diamter of the sphere; this texture suggests that they formed by a volume reduction of the original colloidal particles by approximately 12.5%. The occurrence of hematite nanospheres supports the hypothesis that some ofthe iron was deposited colloidally during the development ofbanded iron formations, approximately 2.5 billion years ago.     

Layer-by-layer growth of binary colloidal crystals

We report the growth of binary colloidal crystals with control over the crystal orientation through a simple layer-by-layer process. Well-ordered single binary colloidal crystals with a stoichiometry of large (L) and small (S) particles of LS2 and LS were generated. In addition, we observed the formation of an LS3 superstructure. The structures formed as a result of the templating effect of the first layer and the forces exerted by the surface tension of the drying liquid. By using spheres of different composition, one component can be selectively removed, as is demonstrated in the growth of a hexagonal non-close-packed colloidal crystal.     

Imaging the sublimation dynamics of colloidal crystallites

We studied the kinetics of sublimating crystals with single-particle resolution by experiments with colloidal spheres and by computer simulations. A short-range attraction between spheres led to crystallites one to three layers thick. The spheres were tracked with optical microscopy while the attraction was reduced and the crystals sublimated. Large crystallites sublimated by escape of particles from the perimeter. The rate of shrinkage was greatly enhanced, however, when the size decreased to less than 20 to 50 particles, depending on the location in the phase diagram. At this size, the crystallites transformed into a dense amorphous structure, which rapidly vaporized. The enhancement of kinetics by metastable or unstable phases may play a major role in the melting, freezing, and annealing of crystals.     

A self-quenched defect glass in a colloid-nematic liquid crystal composite

Colloidal particles immersed in liquid crystals frustrate orientational order. This generates defect lines known as disclinations. At the core of these defects, the orientational order drops sharply. We have discovered a class of soft solids, with shear moduli up to 10(4) pascals, containing high concentrations of colloidal particles (volume fraction φ ? 20%) directly dispersed into a nematic liquid crystal. Confocal microscopy and computer simulations show that the mechanical strength derives from a percolated network of defect lines entangled with the particles in three dimensions. Such a "self-quenched glass" of defect lines and particles can be considered a self-organized analog of the "vortex glass" state in type II superconductors.     

Luminescent colloidal silicon suspensions from porous silicon

A procedure for generating colloidal suspensions of Si that exhibit luminescence, attributed to quantum confinement effects, is described. Samples of n- or p-type Si that have been electrochemically etched to form porous Si can be ultrasonically dispersed into methylene chloride, acetonitrile, methanol, toluene, or water solvents, forming a suspension of fine Si particles that luminesce. Transmission electron microscopy analyses show that the Si particles have irregular shapes, with diameters ranging from many micrometers to nanometers. Luminescent, composite polystyrene/Si films can be made by the addition of polystyrene to a toluene suspension of the Si nanoparticles and casting of the resulting solution onto a glass slide.