Effects of Microcrystalline Cellulose on Suspension Stability of Cocoa Beverage

The rheological properties and particle size distributions of cocoa beverage as well as aggregate structures of solid particles were studied to elucidate the effects of microcrystalline cellulose (MCC) on suspension stability of solid particles in cocoa beverage. Fluidity curve, dynamic viscoelasticity, particle size distribution, and SEM observation were made for beverage samples containing 0.1–0.5 wt% MCC and 11 model samples with various combinations of six ingredients. This revealed that cocoa and MCC particles are highly cohered into an aggregate and the aggregated particles further interact weakly with the milk component, leading to stabilization of the whole system of cocoa beverage.     

Optical and electrical properties of inverted emulsions based on sodium bis(2-ethylhexyl) sulfosuccinate containing cadmium sulfide particles

The optical and electrical properties of inverted emulsions based on sodium bis(2-ethylhexyl) sulfosuccinate (AOT) containing nanoparticles of cadmium sulfide are studied. The particle size of the synthesized samples is determined from UV spectroscopy data. The state of solubilized water in invert emulsions is found to change in the presence of cadmium sulfide due to the formation of aqua complexes. The shape of AOT micelles and the structures formed by drying the invert AOT emulsions are shown to be affected by the degree of hydration and the solubilization of CdS particles.     

Electrophoresis and electric conduction in a salt-free suspension of charged particles

The electrophoresis and electric conduction of a suspension of charged spherical particles in a salt-free solution are analyzed by using a unit cell model. The linearized Poisson-Boltzmann equation (valid for the cases of relatively low surface charge density or high volume fraction of the particles) and Laplace equation are solved for the equilibrium electric potential profile and its perturbation caused by the imposed electric field, respectively, in the fluid containing the counterions only around the particle, and the ionic continuity equation and modified Stokes equations are solved for the electrochemical potential energy and fluid flow fields, respectively. Explicit analytical formulas for the electrophoretic mobility of the particles and effective electric conductivity of the suspension are obtained, and the particle interaction effects on these transport properties are significant and interesting. The scaled zeta potential, electrophoretic mobility, and effective electric conductivity increase monotonically with an increase in the scaled surface charge density of the particles and in general decrease with an increase in the particle volume fraction, keeping each other parameter unchanged. Under the Debye-Hückel approximation, the dependence of the electrophoretic mobility normalized with the surface charge density on the ratio of the particle radius to the Debye screening length and particle volume fraction in a salt-free suspension is same as that in a salt-containing suspension, but the variation of the effective electric conductivity with the particle volume fraction in a salt-free suspension is found to be quite different from that in a suspension containing added electrolyte.     

Influence of physical properties and chemical composition of sample on formation of aerosol particles generated by nanosecond laser ablation at 213 nm

The influence of sample properties and composition on the size and concentration of aerosol particles generated by nanosecond Nd:YAG laser ablation at 213 nm was investigated for three sets of different materials, each containing five specimens with a similar matrix (Co-cemented carbides with a variable content of W and Co, steel samples with minor differences in elemental content and silica glasses with various colors). The concentration of ablated particles (particle number concentration, PNC) was measured in two size ranges (10–250 nm and 0.25–17 µm) using an optical aerosol spectrometer. The shapes and volumes of the ablation craters were obtained by Scanning Electron Microscopy (SEM) and by an optical profilometer, respectively. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using SEM.     

粒径及加热速率对烟煤膨胀特性的影响

将不同粒径烟煤在实验室沉降炉中进行了不同加热速率下的热解实验，研究了煤粉粒径及其加热速率对煤粒膨胀特性的影响。实验结果表明，煤粒在热解过程中发生了明显的膨胀，形成了具有中空结构的煤胞型焦炭，这是煤中较高镜质组体积分数造成的。在相同加热速率下，随粒径减小煤粉颗粒膨胀越剧烈，随粒径增大煤粒膨胀程度之间的差异有减小的趋势。煤样不同膨胀特性是镜质组体积分数不同的结果。镜质组体积分数越高，在热解过程中更容易软化、变形，发生剧烈膨胀。当加热速率从0.5×104K/s升高到4×104K/s时，煤样膨胀程度先增加后减小，表明在0.5×104K/s～4×104K/s，存在一个最佳的加热速率，此时煤粒膨胀程度最高。     

硫化物半导体超微粒量子尺寸效应的光谱研究

用胶体化学方法在水溶液中制备了纳米硫尺寸硫化物半导体超微粒(CdS、ZnS、PbS、及Bi₂S₃),并用TEM测得超微粒颗粒尺寸小于10nm.本文详细研究了这些硫化物半导体超微粒的量子尺寸效应和光学性质以及制备过程中颗粒形成的化学环境与条件参数的影响。可以观察到它们收光谱及喇曼光谱(CdS)的明显变化。采用合适的表面修饰剂和稳定剂、将溶液的pH控制在适当的范围以及金属离子的过量等,都可使超微粒的吸收光谱明显蓝移并出现结构峰。对于CdS超微粒,其特征共振喇曼峰逐渐减弱直至最后消失。这些都表明了硫化物半导体超微粒尺寸逐渐减小而呈现出明显的量子尺寸效应。     

Colloidal Semiconductor Q-Particles: Chemistry in the Transition Region Between Solid State and Molecules

In semiconductor particles of nanometer size, a gradual transition from solid-state to molecular structure occurs as the particle size decreases. Consequently, a splitting of the energy bands into discrete, quantized levels occurs. Particles that exhibit these quantization effects are often called “Q-particles” or, generally, quantized material. The optical, electronic and catalytic properties of Q-particles drastically differ from those of the corresponding macrocrystalline substance. The band gap, a substance-specific quantity in macrocrystalline materials, increases by several electron volts in Q-particles with decreasing particle size. In Q-particles there are approximately as many molecules on the surface as in the interior of the particle. Therefore, the nature of the surface as well as the particle size is also largely responsible for the physico-chemical properties of the particle. Q-particles of many materials can be prepared in the form of colloidal solutions or embedded in porous matrices and are stable over a long period of time. In sandwich colloids, in which Q-particles of different materials are coupled, as well as in porous semiconductor electrodes containing Q-particles in the pores, very efficient primary charge separation is observed. As a result, sandwich colloids have greatly enhanced photocatalytic activity relative to the individual particles, while electrodes modified with Q-particles show high photocurrents. This article deals with the size quantization effect, the synthesis and characterization of Q-particles, as well as with the spectroscopic, electrochemical, and electron-microscopic investigation of these particles.     

Scattering properties of core–shell particles in plastic matrices

Blending submicron rubber particles with plastics can enhance the mechanical strength of the composite material. However, the difference in refractive index between the particle and matrix scatters light, making the material more opaque. We consider the possibility of reducing a particle's scattering cross section by adding coatings. We find that adding coatings can reduce the amount of scattering by changing the effective dielectric contrast between the particle and the matrix. We also found that, when the refractive index of the particle is very close to that of the matrix the order of the layers can have significant effects on the transmitted light. Such effects may be useful for engineering the optical properties of particle‐doped plastics. Resonant effects akin to those found in antireflection coatings on planar surfaces are difficult to obtain and rarely provide a significant reduction in scattering. We discuss theoretical models that can qualitatively explain some of our results. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3534–3548, 2005     

Determination of the effective charge of individual colloidal particles

An optical method is presented that allows simultaneous determination of the diffusion constant and electrophoretic mobility of individual charged particles with radius down to 0.2 mum. By this method the size dependency of the effective charges and zeta potentials of individual particles can be investigated, as well as interparticle interactions and Brownian motion in confined geometries. The diffusion constant and mobility are determined from the power spectrum of the particle speed in a sinusoidal electrical field. The accuracy of the method was tested on PMMA spheres of known size in water. Experiments have been carried out on charged pigment particles with low concentration in a nonaqueous medium containing a charging agent. The mobility is found to be independent of the particle size.     

两亲性Janus粒子的合成及其在Pickering乳液中的应用

Janus粒子由于在光、电、力、磁及表面亲/疏水性等方面表现出各向异性,因此在稳定乳液、生物医药及功能涂层等方面展现出广阔的应用价值.两亲性Janus粒子是指一侧具有亲水性、另一侧具有疏水性的不对称材料,由于同时具有表面活性剂的性质和固体颗粒的效应,在稳定Pickenng乳液方面极具优势.基于此,本文对两亲性Janus...     

Influence of the morphology of barium sulfate nanofibers and nanospheres on the physical properties of polyurethane nanocomposites

Barium sulfate spherical agglomerates and fibers in the nanometric size range were used to prepare polyurethane (PU) nanocomposites (with 1 wt.% concentration) via melt extrusion. A detailed analysis on the effect of the morphology of the barium sulfate phase upon the mechanical, rheological and optical properties was carried out. Results show that the inclusion of the dispersed phase (with various morphologies and sizes) in the polymer matrix does not decrease the polymer mechanical properties, as is observed when particles in the micrometric size range are included. Rheological studies show that the nanocomposite containing spherical particles presents a slightly higher shear viscosity than that of the polymer matrix, in contrast to the nano-fibers viscosity which presents lower values. This is reflected in the effect of the particle morphology on the processability of the material; in contrast, the morphology has no effect on the radio-opacity of the samples. The structure and dispersion of the particles were analyzed using scanning and transmission electron microscopy. The sample with 1 wt.% nanofibers presents better processability than the system with spherical agglomerates maintaining the X-ray opacity properties.     

Optical properties of plasma polymer films with encapsulated silver particles

Plasma polymer thin films with encapsulated small metal particles were prepared by simultaneous plasma polymerization and metal evaporation. Based on transmission electron microscope (TEM) micrographs, particle size and shape were analysed on films with continuously varying filling factor. Thermal annealing causes dramatic changes of the particle size and shape. The optical (UV, VIS, NIR) properties of the films were determined by the UV-absorption of the plasma polymer and by the plasma resonance absorption of the metal particles. The changes in the transmission spectra during thermal annealing were simulated with different effective medium theories. The calculated transmission spectra were fitted to the experimental spectra.     

Optical properties of fractal clusters of small metallic particles

In this paper we describe a method to calculate the optical properties of deterministic fractal clusters. Our method takes advantage of the fact that deterministic fractals can be constructed by an iterative rule. We calculate first the optical properties of a small cluster that describes one stage in the iteration. The optical properties of this cluster are then assigned to an “effective particle”. A small number of these produce the next stage in the fractal construction. We performed the calculations for metallic particles with dielectric functions described by the hydrodynamic model. Results in the dipolar and quadrupolar approximations for a cluster at the second fractal stage shows the double extinction peak often seen in experimental studies.     

Biomolecule induced nanoparticle aggregation: effect of particle size on interparticle coupling

Gold nanoparticles of variable sizes have been prepared by reducing HAuCl(4) with trisodium citrate by Frens' method. It has been found that the gold particles under consideration produce well-ordered aggregates upon interaction with a biomolecule, glutathione in variable acidic pH condition and exhibit pronounced changes in their optical properties arising due to electromagnetic interaction in the close-packed assembly. The effect of nanoparticle size on the nature of aggregation as well as the variation in the optical response due to variable degree of interparticle coupling effects amongst the gold particles have been investigated. The optical properties of the gold aggregates have been accounted in the light of Maxwell-Garnett effective medium theory considering the changes in the filling factor in different aggregates produced by variable sizes of gold colloids. The aggregates have been characterized by UV-vis spectroscopy, FTIR, Raman, XRD and TEM studies. It has been observed that a new peak appearing at a longer wavelength intensifies and shifts further to the red from the original peak position depends on the particle size, concentration of glutathione and pH of the solution. On the basis of the first appearance of a clearly defined new peak at longer wavelength, a higher sensitivity of glutathione detection has been achieved with gold nanoparticles of larger dimension.     

Electronic excitations in many-particle systems: a quantitative analysis

Small particles, produced in usual experiments, commonly form many-particle systems. Interactions of various kinds among the particles influence the properties of such systems. We consider here the optical properties of noble metal particle systems with separated nearly spherical particles and with aggregates formed by induced coagulation of the single particles. In order to describe their optical extinction we apply electrodynamic interaction models on particles and aggregates. We perform a quantitative analysis of the extinction spectrum of one selected sample with the electrodynamic interaction model.     

Design and Synthesis of Transparent Poly （acrylonitrile-butadiene-styrene） and Relationship Between Its Phase Construction and Transparency

IntroductionABS resins have been widely applied to the field ofengineering materials because of their excellent me-chanical,electrical,physical,and chemical proper-ties.Typically,ABS resins comprise a rigid copolymermatrix-phase dispersed in a graft copol…     

Nanoparticle composition of a ferrofluid and its effects on the magnetic properties

Experiments were carried out on a water-based ferrofluid (gamma-Fe2O3 with carboxydextran shell) using photon correlation spectroscopy (PCS), atomic force microscopy, and magnetic nanoparticle relaxation measurements. The experiments were designed with the aim to relate the Néel signals that are in theory generated by large single core particles with nanoscopic properties, that is, particle size, particle size distribution, shell properties, and aggregation. For this purpose, the ferrofluid was fractionated by magnetic fractionation and size exclusion chromatography. Nanoparticles adsorbed onto positively charged substrates form a two-dimensional monolayer. Their mean core diameters are in the range of 6 to about 20 nm, and particles above 10 nm are mostly aggregates. The hydrodynamic particle diameters are between 13 and 80 nm. The core diameter of the smallest fraction is confirmed by X-ray reflectometry; the surface coverage is controlled by bulk diffusion. Comparison with the hydrodynamic radius yields a shell thickness of 3.8 nm. Considering the shell thickness to be constant for all particles, it was possible to calculate the apparent particle diameter in the original ferrofluid from the PCS signals of all fractions. As expected, the small cores yielded no Néel relaxation signals in freeze-dried samples; however, the fractions containing mostly aggregates yielded Néel relaxation signals.     

Nonlinear optical response of chloroaluminiumphthalocyanine encapsulated by silica core-shell particles

We report for the first time on the synthesis of core-shell particles containing chloroaluminiumphthalocyanine (ClAlPc) prepared using a sol-gel technique. These particles have the dye molecules at the core, encapsulated by silica shell. The mean size of the particle is determined from HRTEM studies and is found to be approximately 0.08 microm. The surface and bulk compositions of the core-shell particles are studied by XPS and EDAX measurements, respectively. Time-resolved fluorescent measurements indicate a decrease in fluorescence lifetime for the core-shell particles as compared to that of bare dye dissolved in ethanol. This is analyzed on the basis of available theoretical models. Third-order nonlinear optical effects are investigated by the Z-scan technique using 8 ns pulses at a wavelength of 532 nm from a frequency-doubled Nd:YAG laser. The analysis indicates that both singlet and triplet excited-state absorption contribute to nonlinear absorption.     

乳液聚合法制备纳米金/聚苯乙烯复合粒子

以氯金酸为前驱体,十二烷基硫醇和硼氢化钠分别作为稳定剂和还原剂,采用相转移法制备了单分散的金纳米粒子.将金纳米粒子通过乳液聚合的方法制备了纳米金/聚苯乙烯复合粒子.通过紫外-可见吸收光谱(UV-Vis)研究了纳米金和纳米金/聚苯乙烯复合粒子的光吸收特性,使用傅立叶变换红外光谱(FT-IR)、X射线衍射(XRD)、透射电子显微镜(TEM)和动态光散射(DLS)对产物的组成、晶体结构、形貌、以及粒径进行了表征.结果表明,复合粒子为粒径分布较窄的球形,其中的金纳米粒子为面心立方结构.热失重分析(TGA)说明制备的纳米金/聚苯乙烯复合粒子具有很好的热稳定性.     

Influence of Surface-Active Soap Dispersants on the Size of Calcium Soap Particles Formed in Hard Water

Average particle radii of dilute calcium oleate dispersions containing various efficient surfactants-dispersants of calcium soap are calculated from the data on optical density. The effect of the surfactant on the particle sizes and kinetics of their variations during two hours are studied. Dispersing efficiency does not always correlates with the turbidity and average radius of the particles formed in hard water.