纳微米颗粒的表面改性及其在Pickering乳液中的应用进展

以固体粒子替代表面活性剂稳定的Pickering乳液,不仅可以赋予乳液许多特殊的性能(电磁和温度感应性能等),还可消除由添加表面活性剂所带来的副作用(过敏性和毒性等),这使得Pickering乳液可以应用到对表面活性物质具有很大限制的生物材料领域。系统综述了常见Pickering乳液用固体粒子,以及为了获得不同类型的乳液而对固体粒子进行表面改性的主要方法,着重归纳了表面改性前亲水性羟基磷灰石(HAp)和改性后疏水性HAp作为颗粒乳化剂稳定的Pickering乳液的类型及其进一步合成的产物。     

Control of Particle Adsorption for Stability of Pickering Emulsions in Microfluidics

Studying the stability of Pickering emulsion is of great interest for applications including catalysis, oil recovery, and cosmetics. Conventional methods emphasize the overall behavior of bulk emulsions and neglect the influence of particle adsorbing dynamics, leading to discrepancies in predicting the shelf‐life of Pickering emulsion–based products. By employing a microfluidic method, the particle adsorption is controlled and the stability of the Pickering emulsions is consequently examined. This approach enables us to elucidate the relationship between the particle adsorption dynamics and the stability of Pickering emulsions on droplet‐level quantitatively. Using oil/water emulsions stabilized by polystyrene nanoparticles as an example, the diffusion‐limited particle adsorption is demonstrated and investigated the stability criteria with respect to particle size, particle concentration, surface chemistry, and ionic strength. This approach offers important insights for application involving Pickering emulsions and provides guidelines to formulate and quantify the Pickering emulsion–based products.     

Formation and stabilization of Pickering emulsions using salt-sensitive core–shell cationic nanoparticles

Pickering emulsions known for their solid emulsifiers and brilliant stability characters have attracted many researchers’ attention. The controlled stability and demulsification of emulsion are necessary in some cases such as crude oil extraction and drug release. Stimuli-responsive Pickering emulsion could provide suitable controllability and emerged in the last decade. Among various controllable factors, salt ion is known as a critical parameter, but it is rarely investigated. Here, core–shell cationic nanoparticles with a poly-(2-aminoethyl methacrylate hydrochloride) shell and a polystyrene core were used in the preparation of Pickering emulsion. The size and morphology of nanoparticles were monitored by transmission electron microscopy and dynamic light scattering. The microstructure and stability of the formed Pickering emulsion were studied via dynamic light scattering and a polarizing optical microscope under various salt ion types and concentrations. The effect of salt types (Cl^?, ClO₄^?, and PO₄^3?) and salt concentrations on the Pickering emulsion was investigated. Cl^?, ClO₄^?, and PO₄^3? are in situ generated from NaCl, NaClO₄, and (NaPO₃)₆, respectively. It showed that PO₄^3? (100–1000 mM) was unable to form stable Pickering emulsion, while Cl^? and ClO₄^? could induce stable Pickering emulsions under optimized conditions. Furthermore, after increasing the salt concentration over a critical salt concentration, the Pickering emulsion underwent rapid demulsification. This work revealed the effects of salt on size, conformation, charge, wettability, interaction, and adsorption state of nanoparticles and proposed the stability mechanisms of the Pickering emulsion. This opened up more potential applications in the field of controlled demulsification, petroleum recovery, catalyst recovery, and so on triggered by salt ions.

Graphical abstract

Salt could affect the size, conformation, and interaction of core–shell cationic nanoparticles, which then affect the formation mechanism and stability properties of Pickering emulsions from them.

     

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.     

Interparticle photo-cross-linkable Pickering emulsions for rapid manufacturing of complex-structured porous ceramic materials

A new series of Pickering emulsions that can be photo-cured by interparticle photo-cross-linking reactions using small amounts of multifunctional acrylate (MA) monomers is proposed to rapidly manufacture complex-structured porous ceramic materials. In our new process, water in oil (w/o) Pickering emulsion was designed by vigorous mixing of water and polyethyleneimine partially complexed with oleic acid (PEI–OA)-stabilized SiO₂/toluene suspension containing small amounts of MA and a photo-radical initiator. Ultraviolet light irradiation to this w/o Pickering emulsion induced the formation of interparticle photo-crosslinks, which resulted in successful photocuring by photo-radical polymerization of MA and the Michael addition reaction between the polymerized MA and PEI–OA on the particles in the oil phase. We further applied the newly designed photo-curable Pickering emulsion and demonstrated that SiO₂ components with pores related to the dispersed aqueous phase and complexed outer structures could be shaped via silicone molding or a hybridized approach of photocuring and green machining. Because of the reduced amounts of MA used, the porous SiO₂ green components could be heat-treated using rapid heating profiles without any structural collapse for dewaxing and partial sintering.     

One-pot fabrication of magnetic nanocomposite microcapsules

Fe₂O₃ nanoparticles can self-assembly at liquid-liquid interfaces to form stable water-in-oil Pickering emulsions. Novel magnetic and thermo-sensitive microcapsules were one-pot fabricated by radical polymerization of N-isopropylacrylamide (NIPAm) at the aqueous phases of Pickering emulsions at 60 °C. The obtained PNIPAm was deposited from the water phases onto the interfaces of water-in-oil Pickering emulsions to form Fe₂O₃/PNIPAm nanocomposite shells because of its hydrophobicity at this reaction temperature. Pickering emulsion polymerization opens up a new route to fabricate a variety of hollow and hybrid microcapsules.     

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.     

Emulsification and analyzing of oil in water emulsion by implementation of image processing method

ABSTRACT

Although a considerable amount of work has been done on emulsions, particularly regarding their relative stability, it is hard to find a method giving us an overall view about the amount of internal phase (AIP) in emulsions. Discussing this method and putting forward a way to evaluate these parameters is the aim of this paper. In this paper, image processing method is applied to quantify “Amount of Internal phase” in an emulsion. AIP is the parameter that shows the ratio of dispersed phase to the sum of internal and external phases of an emulsion. Microscopic observations of emulsions are fed into a program provided using MATLAB to compute AIP. A series of experiments have been carried out and chemical oxygen demand, COD, is used as a verification parameter. Results derived from image processing and COD tests are in agreement with each other and altogether showed that image processing will be able to be applied as a powerful tool in various applications of emulsions.     

PARTICLE COUNTING OIL AND WATER EMULSIONS

ABSTRACT

Because of their speed and convenience, optical particle counters are widely used for particle size analysis of liquid samples. In some cases, both solid particles and emulsified water or oil may be present in a sample. Since emulsion droplets are counted as if they are solid particles, analysis and data interpretation for these samples are difficult. Until recently, no suitable method existed for distinguishing solid contaminants from emulsion droplets. This paper discusses a method which overcomes this limitation. Through the use of a surfactant-laden nonpolar dilution fluid, water is incorporated into reverse micelles too small to be seen by most optical particle counters. As a result, only solid contaminants are counted, and many problems associated with the analysis of emulsions are overcome. Results obtained from a wide range of oil and water emulsions are used to evaluate the merits and possible applications of the new technique.     

Polymer microspheres stabilized by titania nanoparticles

Polymer microspheres stabilized by titania nanoparticles were synthesized using a two-step Pickering emulsion polymerization process, in which nanosized titania nanoparticles were used as solid emulsifiers and building blocks. It gives a simple but novel route for the fabrication of functional inorganic/polymer hybrid materials with controlled microstructures. The final Pickering emulsion can be applied to various substrates forming continuous films with highly ordered nanosized to microsized TiO₂ protuberances across the films. Those films will have potential applications for photo-catalyst, water and air purification.     

Dynamically Reconfigurable,Multifunctional Emulsions with Controllable Structure and Movement

Dynamically reconfigurable oil‐in‐water (o/w) Pickering emulsions are developed, wherein the assembly of particles (i.e., platinum‐on‐carbon and iron‐on‐carbon particles) can be actively controlled by adjusting interfacial tensions. A balanced adsorption of particles and surfactants at the o/w interface allows for the creation of inhomogeneity of the particle distribution on the emulsion surface. Complex Pickering emulsions with highly controllable and reconfigurable morphologies are produced in a single step by exploiting the temperature‐sensitive miscibility of hydrocarbon and fluorocarbon liquids. Dynamic adsorption/desorption of (polymer) surfactants afford both shape and configuration transitions of multiple Pickering emulsions and encapsulated core/shell structured can be transformed into a Janus configuration. Finally, to demonstrate the intrinsic catalytic or magnetic properties of the particles provided by carbon bound Pt and Fe nanoparticles, two different systems are investigated. Specifically, the creation of a bimetallic microcapsule with controlled payload release and precise modulation of translational and rotational motions of magnetic emulsions are demonstrated, suggesting potential applications for sensing and smart payload delivery.     

Water-in-Water Emulsions Stabilized by Silica Janus Nanosheets

Water-in-water (w/w) emulsions have been recognized for their broad applications in foods, cosmetics, and biomedical engineering. In this work, silica Janus nanosheets (JNs) with polyacrylic acid (PAA) chains grafted on one surface via crushing functional silica foams, and used silica JNs as Pickering stabilizer to produce stable water-in-water (w/w) emulsions from the aqueous two-phase system (ATPS) containing methacrylic acid (MAA) and NaCl are prepared. The interfacial area of w/w emulsions increases linearly with the concentration of silica JNs, and the interfacial coverage of nanosheets is calculated to be about 98%. After polymerizing w/w emulsions prepared from MAA/NaCl ATPS, it is found that silica JNs are entrapped at the interface of w/w emulsions with the smooth PAA-grafted surface located toward MAA-rich phase due to their specific interaction. These results show that functional silica JNs can be used as a promising amphiphilic Pickering stabilizer to produce well-defined w/w emulsions for numerous application fields.     

凸棒颗粒稳定的橄榄油／水型Pickering乳状液的制备条件及形成机理研究

选取凹凸棒作为乳化剂,系统研究pH、颗粒浓度、油相体积分数以及不同价态盐对橄榄油／水型Pickering乳状液稳定性的影响,结果表明,体系pH在4～9范围内可制备出稳定的乳状液;颗粒浓度的提高可增强乳液的分层和聚结稳定性;乳液液滴直径随油相体积分数的增加先增大后减小;无机盐的引入不会对乳液相及水相的体积产生影响,但对乳液液滴的尺寸分布影响显著,其中NaCl浓度的增加有利于乳状液液滴数均直径的增加,而CaCl2浓度增加时,乳状液液滴数均直径呈现先增大后减小的变化趋势。研究表明,凹凸棒可作为一种新型纳米乳化剂应用于绿色乳状液的制备。     

Prolonged Tissue Levels of Pentazocine from Multiple W/O/W EMULSIONS IN MICE

Abstract

Multiple W/O/W emulsions containing pentazocine were prepared and tested in virto and in viro. The in viro results indicated a well controlled and higher drug release from teh W/O/W emulsions than the W/O emulsion. The in vivo data showed prolonged tissue levels of pentazocine after oral administration of W/O/W emulsions than the W/O emulsion to mice in comparison to acquenous drug solution and W/O emulsion.     

纳米纤维素凝胶微粒及其在Pickering泡沫中的应用

目的研究氧化纳米纤维素/乳酸链球菌素(TONCC/nisin)凝胶粒子的性质及其在环保抗菌泡沫中的应用。方法利用TONCC的表面羧基基团与nisin的表面阳离子的吸附耦合作用,制备TONCC/nisin水凝胶和微凝胶,以微凝胶作为稳定粒子,环氧大豆油丙烯酸酯(AESO)为油相,制备TONCC/nisin/AESO Pickering乳液,对水凝胶、微凝胶、乳液的稳定性进行研究;通过热固化乳液得到环保抗菌的泡沫材料,并对泡沫材料的结构和抗菌效果进行表征。结果水凝胶的结构随着在水中浸泡时长的增加而发生变化,宏观表现为坍塌变形,nisin逐渐析出,微凝胶随着静置时间的延长其粒径变化不大;以微凝胶作为界面稳定剂的AESO乳液的热稳定性较好,在90℃下加热30 min乳液液滴并未发生聚并现象,该乳液固化后形成的多孔泡沫材料对李斯特菌的抑制作用明显,当泡沫中nisin含量为2μg/g时,其抑菌率为43%。结论TONCC和nisin形成的微凝胶粒子在水中稳定性较好,可以用于乳化AESO制备Pickering泡沫,同时赋予泡沫多孔性和抗菌性,在制备环保抗菌泡沫方面有很大的应用潜力。     

Facile Fabrication of Monodisperse Micron-Sized Dual Janus Silica Particles with Asymmetric Morphology and Chemical Environment

Janus particles are a kind of materials with asymmetric morphology or surface chemical environment. But so far, the preparation of particles with dual asymmetry is still a challenging problem. Hence the cation surfactant hexadecyl trimethyl ammonium bromide and co-surfactant octadecylamine are applied to improve the Pickering emulsion stability, and the micron-sized silica particles are arranged in a single layer at the toluene–water interface through electrostatic interaction. Furthermore, organosilane reagents are added in the preparation process, resulting in the construction of asymmetric hydrophilic or hydrophobic mesoporous precisely onto the micron-sized silica particles surface. The cation surfactant-assisted Pickering emulsion method is simple, effective, and convenience, which can be applied in the synthesis of various dual Janus silica particles for specific applications.     

Release of Methotrexate from Microsphere-In-Oil-In-Water Emulsions

Abstract

The in vivo and in vitro release characteristics of methotrexate from the microsphere-in-oil-in-water emulsions were studied. The results demonstrated a rapid and slow biphasic release profiles for the emulsions. This may be due to the release of methotrexate from the external aqueous phase of the emulsion for the rapid release phase and from the internal microsphere for the slow release phase. The addition of phosphatidylcholine in the emulsions resulted in a slower release of the methotrexate which may be caused by the formation of phospholipid layers on the surface of the emulsion particles to hinder the release of the drug from the emulsions.     

VAE/PVC-VDC共混乳液的研究

此共混乳液采用乙烯－醋酸乙烯共聚物（ＶＡＥ）乳液和氯乙烯－偏氯乙烯共聚物（ＰＶＣ－ＶＤＣ）乳液以机械共混方法制得。考察了其微观形态、流变性及其成膜后的力学性能等，发现共混乳液具有一定的相容性，其拉伸强度与ＶＡＥ胶膜相比有很大的提高。     

基于海藻酸自组装胶体粒子的制备及其乳化性能

用海藻酸(ALG)和溶菌酶(Lys)静电自组装制备胶体粒子,用纳米粒度仪和透射电镜对其尺寸和形貌进行表征,研究了溶菌酶和海藻酸的质量比(WR)对胶体粒子性质的影响,得到了具有最佳WR的胶体粒子。胶体粒子具有球形结构,粒径约为143 nm。这种胶体粒子可二次组装在油水界面稳定水包油型Pickering乳液,研究了pH值和盐浓度对胶体粒子性质和乳化性能的影响。随着pH值的增大胶体粒子和乳液滴粒径均逐渐增大而乳化性能逐渐降低; 随着盐浓度的提高胶体粒子和乳液滴的粒径先减小后增大,乳化性能先提高后降低。乳液均保留了一定的活性。     

Programmatically Dynamic Microcompartmentation in Coacervate-in-Pickering Emulsion Protocell

The desire for exploration of cellular functional mechanisms has substantially increased the rapid development of artificial cells. However, the construction of synthetic cells with high organizational complexity remains challenging due to the lack of facile approaches ensuring dynamic multi-compartments of cytoplasm and stability of membranes in protocells. Herein, a stable coacervate-in-Pickering emulsion protocell model comprising a membraneless coacervate phase formed by poly-l -lysine (PLys) and adenosine triphosphate (ATP) encapsulated in Pickering emulsion is put forward only through simple one-step emulsification. The dynamic distribution of intracellular components (coacervates in this protocell model) can be manipulated by changes in temperature or pH. This coacervate-in-Pickering emulsion protocell system exhibits repeatable cycle stability in response to external stimuli (at least 24 cycles for temperature and 3 cycles for pH). By encapsulating antagonistic enzymes into coacervates, glucose oxidase (GOx) and urease as an example, the control of local enzyme concentration is achieved by introducing glucose and urea to adjust the pH value in Pickering emulsion droplets. This hybrid protocell model with programmatically dynamic microcompartmentation and sufficient stability is expected to be further studied and applied in cellular biology, facilitating the development of lifelike systems with potential in practical applications.