Drying oil-in-water Pickering emulsions to make redispersible powders

We report on the formation of powder by drying oil-in-water emulsions stabilized by silanised silica nanoparticles. Drying was achieved by spraying fine droplets (up to a hundred micrometres in diameter) of the emulsions into a chamber of hot, flowing air. We show that the surfaces of droplets of the emulsions become enriched with nanoparticles as the water evaporates in the drying chamber. Controlling the relative amounts of oil and particles in the droplets being dried is the key to encapsulating the oil drops within the powder. Dried Pickering emulsions containing up to 40 wt% encapsulated oil that could be dispersed in water as drops of the same size as in the original emulsion were produced.     

Internal-Image Formation and Related Photographic Effects

In accordance with generally accepted views, it is shown that variations in degree of Clayden and Villard effects and in Solarizability can be broadly correlated with the surface/internal speed ratio. In particular it is shown that increase of surface/internal speed ratio by increase of digestion time, or simply by increase of exposure time, leads to a decrease in the Villard effect, and that solarizability can be greatly enhanced by kinking which increases internal sensitivity without much effect on surface response. However, among collections of commercial emulsions, correlations between surface/internal speed ratio and latent-image effects involving rehalogenation processes are masked by differences in the halogen-accepting properties of the emulsions. Observations on the Villard effect support the view that the grains which do not form surface image readily are the more sensitive ones for internal-image formation, and this should be recognised in attempting to deduce ratios of surface to internal speed.     

不同油相对负载茶多酚的多重乳液稳定性的影响

采用高压均质和高速剪切的方法,观察其制备的初乳对多重乳液稳定性的影响,并研究了大豆油、芥花油、油茶籽油和葵花籽油四种不同的植物油作为油相对多重乳液稳定性的影响,实验结果表明,用高压均质方法制备的初乳能够获得稳定的、外观细腻的多重乳液。四种不同的油相制备的多重乳液在4000r/min,15min的离心条件下不分层;大豆油作为油相制备的多重乳液在室温下放置两个月分层,芥花油、油茶籽油和葵花籽油,在室温下放置三个月不分层。对四种不同油相制备的多重乳液的粒径进行测量,实验结果表明,油茶籽油的D0.1,D0.5和D0.9三个数据的粒径的稳定性比较好。     

Response of standard silver halide emulsions to mid-infrared radiation

It is shown, to our knowledge for the first time, that commercially available silver halide film emulsions may be used to record infrared radiation (10.6 μm) without the use of visible light as the coactivator. We present a film characterization study.     

Study on high performance ice slurry formed by cooling emulsion in ice storage (discussion on adaptability of emulsion to thermal storage material)

This study focuses on an emulsion as a new thermal storage material for ice storage. Two types of emulsions were formed using an oil–water mixture with a small amount of additive. A silicone, light and lump oils were used. The water contents of the emulsions were 70, 80 and 90%. The additive was an amino group modified silicone oil. No depression of freezing point was observed for the emulsions because of their hydrophobic properties. In order to determine the structure of the emulsions, their electrical resistances were measured. Moreover, components of the liquids separating from the emulsions were analyzed. The results indicated that one emulsion was a W/O type emulsion, while the other was an O/W type. Finally, adaptability of the two emulsions to ice storage was discussed, it was concluded that a high performance ice slurry could be formed by the W/O type emulsion.     

Topical delivery of fluconazole: in vitro skin penetration and permeation using emulsions as dosage forms

We investigated in vitro skin penetration and permeation of fluconazole from emulsions containing different penetration enhancers. Fluconazole permeation was high (15-65% of the applied dose) across hairless mouse skin and low (8-9%) across pig ear skin. Permeation across mice skin from a formulation containing propyleneglycol and isopropyl myristate was significantly higher than that observed with the paraffin oil and propyleneglycol or Transcutol® emulsions. With pig skin, the paraffin oil or isopropyl myristate and propyleneglycol emulsions showed similar skin permeation and penetration. However, these emulsions provided epidermal concentrations higher than the minimal inhibitory concentrations for most dermatophytes.     

Topical Delivery of Fluconazole: In Vitro Skin Penetration and Permeation Using Emulsions as Dosage Forms

ABSTRACT

We investigated in vitro skin penetration and permeation of fluconazole from emulsions containing different penetration enhancers. Fluconazole permeation was high (15–65% of the applied dose) across hairless mouse skin and low (8–9%) across pig ear skin. Permeation across mice skin from a formulation containing propyleneglycol and isopropyl myristate was significantly higher than that observed with the paraffin oil and propyleneglycol or Transcutol® emulsions. With pig skin, the paraffin oil or isopropyl myristate and propyleneglycol emulsions showed similar skin permeation and penetration. However, these emulsions provided epidermal concentrations higher than the minimal inhibitory concentrations for most dermatophytes.     

Microstructure evolution of water-oil emulsions in high-frequency and microwave electromagnetic fields

We investigate the impact by high-frequency (HF) and microwave electromagnetic (EM) fields on the microstructure of oil-water emulsions. The laboratory stand for those studies is described. We present the investigation results showing the patterns of the evolution of the water-oil emulsions depending on the EM field parameters and the dielectric properties of the emulsions.     

Investigation of AGFA-8E56HD photographic emulsion and relief hologram structures by atomic force microscopy

Relief holograms are obtained on Agfa 8E56HD holographic emulsions by a Russian chemical-processing technique that is developed for their PE-2 holographic emulsion. We have shown that the three-dimensional surface profiles can easily be visualized by applying atomic force microscopy to measurement of the relief depth and relief spacing on holographic emulsions. The relief depth and thus diffraction efficiency decreases with increasing exposure time.     

Design and development of multiple emulsion for enhancement of oral bioavailability of acyclovir

The objective of this investigation was to design and develop water-in-oil-in-water type multiple emulsions (w/o/w emulsions) entrapping acyclovir for improving its oral bioavailability. Multiple emulsions (MEs) were prepared and optimized using Span-80 and Span-83 as lipophilic surfactant and Brij-35 as hydrophilic surfactant. The physio-chemical properties of the w/o/w emulsions - particle size, viscosity, phase separation (centrifugation test) and entrapment efficiency were measured and evaluated along with macroscopic and microscopic observations to confirm multiple nature, homogeneity and globule size. Stability study, in vitro and ex vivo release studies were performed followed by in vivo studies in rats. Stable w/o/w emulsions with a particle size of 33.098 ± 2.985 µm and 85.25 ± 4.865% entrapment efficiency were obtained. Stability studies showed that the concentration of lipophilic surfactant was very important for stability of MEs. Drug release from the prepared formulations showed initial rapid release followed by a much slower release. In vivo studies in rats indicated prolonged release and better oral bioavailability as compared to drug solution. The overall results of this study show the potential of the w/o/w emulsions as promising drug delivery systems for acyclovir.     

Non-equilibrium simulation of optically trapped colloidal particles at liquid interfaces

A theoretical study of the non-equilibrium behaviour of colloidal particle monolayers under the influence of the displacement of a single, optically trapped colloidal particle is presented. Two different types of monolayer (i.e., one relatively rigid and the other relatively soft) confined to a liquid–liquid interface are investigated using the Stokesian dynamics simulation technique. An effective dipole–dipole interaction is assumed to act between the colloidal particles and viscous drag forces acting on the particles are taken into account. The calculations reveal periodic oscillations of the net force on the trapped particle for the soft monolayer and highly non-linear, non-monotonic variations for the rigid monolayer. The highly non-linear variations of the net force for the rigid monolayer are concomitant with rapid, cooperative particle rearrangements and large oscillations in the global orientational order parameter of the monolayer. These findings, combined with the results of optical-tweezer experiments, should be useful for the rheology of liquid interfaces and the investigation of Pickering emulsions.     

Effect of Dextrose in the Internal Aqueous Phase on Formation and Stabiblity of W/O/W Multiple Emulsions

The osmolarity of the internal aqueous phase of W/O/W multiple emulsions was varied by using different concentrations of dextrose in the internal phase. Evaluation of the stability of the emulsions was done by microscopic, viscometric and conductometric methods. Microscopic study indicated that as the dextrose concentration in the internal phase increased (0 - 2.50% W/V), the stability, in terms of coalescence of the internal droplets and rupture of the interfacial oily layer, increased from 12 hrs to 7-8 weeks. Viscometric evaluation showed the emulsions to exhibit Non-Newtonian flow and the apparent viscosities of freshly prepared emulsions increased from 8000 to 56,000 cps as the dextrose concentration was increased; the viscosity decreased as the emulsion aged. The amount of drug released as determined by the conductometric method, correlated with the viscosity and stability of the emulsions. The reduction of globule size of the primary (W/O) phase by use of a colloid mill increased the apparent viscosity significantly and thus improved the stability of the formulations.     

Graphitic Carbon Nitride Stabilizers Meet Microfluidics: From Stable Emulsions to Photoinduced Synthesis of Hollow Polymer Spheres

Graphitic carbon nitride (g‐CN) has been utilized as a heterogeneous catalyst, but is usually not very well dispersible. The amphiphilic character of g‐CN can be altered by surface modifications of g‐CN nanopowders. Introducing hydrophilicity or hydrophobicity is a promising avenue for producing advanced emulsion systems. In this study, a special surface‐modified g‐CN is used to form stable Pickering emulsions. Using a PDMS‐based microfluidic device designed for stable production of both single and double emulsions, it is shown that surface‐modified g‐CNs allow the manufacture of unconventionally stable and precise Pickering emulsions. Shell thickness of the double emulsions is varied to emphasize the robustness of the device and also to demonstrate the extraordinary stabilization brought by the surface‐modified carbon nitride used in this study. Due to the electrostatic stabilization also in the oil phase, double emulsions are centered. Finally, when produced from polymerizable styrene, hollow polymer microparticles are formed with precise and tunable sizes, where g‐CN is utilized as the only stabilizer and photoinitiator.     

Effect of Dextrose in the Internal Aqueous Phase on Formation and Stabiblity of W/O/W Multiple Emulsions

Abstract

The osmolarity of the internal aqueous phase of W/O/W multiple emulsions was varied by using different concentrations of dextrose in the internal phase. Evaluation of the stability of the emulsions was done by microscopic, viscometric and conductometric methods. Microscopic study indicated that as the dextrose concentration in the internal phase increased (0 – 2.50% W/V), the stability, in terms of coalescence of the internal droplets and rupture of the interfacial oily layer, increased from 12 hrs to 7-8 weeks. Viscometric evaluation showed the emulsions to exhibit Non-Newtonian flow and the apparent viscosities of freshly prepared emulsions increased from 8000 to 56,000 cps as the dextrose concentration was increased; the viscosity decreased as the emulsion aged. The amount of drug released as determined by the conductometric method, correlated with the viscosity and stability of the emulsions. The reduction of globule size of the primary (W/O) phase by use of a colloid mill increased the apparent viscosity significantly and thus improved the stability of the formulations.     

Current Trends in Pickering Emulsions: Particle Morphology and Applications

In recent years, Pickering emulsions and their applications have attracted a great deal of attention due to their special features, which include easy preparation and enhanced stability. In contrast to classical emulsions, in Pickering emulsions, solid microparticles or nanoparticles that localize at the interface between liquids are used as stabilizers, instead of surfactants, to enhance the droplet lifetime. Furthermore, Pickering emulsions show higher stability, lower toxicity, and stimuli-responsiveness, compared with emulsions that are stabilized by surfactants. Therefore, they can be considered attractive components for various uses, such as photocatalysis and the preparation of new materials. Moreover, the nanoparticle morphology strongly influences Pickering emulsion stability as well as the potential utilization of such emulsions. Here, we review recent findings concerning Pickering emulsions, with a particular focus on how the nanoparticles morphology (i.e., cube, ellipsoid, nanosheet, sphere, cylinder, rod, peanut) influences the type and stability of such emulsions, and their current applications in different fields such as antibacterial activity, protein recognition, catalysis, photocatalysis, and water purification.     

银二聚体掺杂与甲酸根掺杂立方体溴化银乳剂的协同增感研究

使用反馈式微机控制双注仪，在晶体生长过程中的某一时刻，一定pAg下，同时加入一定浓度的二甲基胺硼烷（DMAB）和一定浓度的甲酸盐，分别制得了甲酸根离子处于晶体次表面位置的立方溴化银微晶乳剂和Ag2与甲酸根同处于晶体次表面的立方溴化银微晶乳剂。对此两份乳剂感光性能的测试结果表明：（1）单独甲酸盐掺杂乳剂与Ag2、甲酸根协同掺杂乳剂相比，二者感光度相同；（2）单独甲酸盐掺杂乳剂与Ag2、甲酸根协同掺杂乳剂相比，二者经常规的硫加金化学增感和光谱增感后，前者增感明显优于后者；（3）卤化银颗粒内部的Ag2或甲酸根掺杂可同时与常规的表面硫加金增感和光谱增感进行协同增感；（4）所有的掺杂乳剂，包括原始、硫加金和光谱增感的掺杂乳剂，它们的灰雾均保持在低水平。     

Double-liquid micromanometer for measuring small pressure differences in rarefied gases

Conclusions The above model of a double-liquid micromanometer has been in use for the past six months. During this period no noticeable changes in the physicochemical properties of the liquid have been observed. The dividing line remained clearly visible. Vacuum sealing was not disturbed by displacing the instrument. The manometer legs were separated only during measurements. It was, therefore, possible to avoid sharp variations of pressure differences in the measuring legs of the micromanometers. Formation of emulsions was not observed under normal operating conditions of the instrument.     

Comparison of direct,rehalogenating, and solvent bleaching processes with BB-640 plates

Bleaching is one of the key processes in the production of phase holograms with fine grain silver halide emulsions. This step was widely studied for discontinued Kodak, Agfa, and Ilford emulsions, and most of those results have been optimized with small changes for presently available holographic emulsions. A study of the different bleaching techniques with BB-640 holographic emulsions is presented. Some interesting new features found are the high-diffraction efficiencies achieved with direct rehalogenating bleaching and with reversal bleaching, with higher values and better sensitivities than those of classical fixation-free rehalogenating bleaching. In particular, we have found that the highest diffraction efficiency and the lowest scattering is obtained with AAC developer and reversal bleach R-9, with diffraction efficiency values of 82%.     

快速彩纸氯化银立方晶体外延溴化银乳剂制备方法的研究

外延量在0—5个摩尔百分数范围研究其对氯化银立方晶体外延溴化银乳剂照相性能的影响,并探讨三种供快速彩纸用乳剂的制备途径。     

介质弹性对多重乳液分散度的影响

多重乳液的单分散性是与粒径相关的一些重要性质如乳液稳定性、乳化剂界面分配等研究工作的基础.在保证连续相与分散相的粘度比∈(0.1,1)条件下,分别以聚丙烯酰胺及甘油为连续相,以不同内相体积w1/o一级乳液为分散相,在相应流变性质研究的基础上,研究了介质的弹性对多重乳液分散度的影响,制备了分散度20%左右的拟单分散多重乳液体系.研究表明,连续相的弹性是制备拟单分散多重乳液的必要条件,分散相的弹性有利于单分散多重乳液的制备.完善了前人的相关研究结果.