Pickering emulsions stabilized by sphere-spheroid mixtures
02 Nov 2021-Journal of Dispersion Science and Technology (Informa UK Limited)-Vol. 42, Iss: 13, pp 2022-2031
TL;DR: Stable oil-in-water Pickering emulsions (PEs) are prepared by using hydrophilic and oppositely charged spherical (silica) and nonspherical (hematite) nanoparticle mixture as discussed by the authors.
Abstract: Stable oil-in-water Pickering emulsions (PEs) are prepared by using hydrophilic and oppositely charged spherical (silica) and nonspherical (hematite) nanoparticle mixture. By varying aqueous disper...
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TL;DR: In this article, it is shown that the association between oppositely charged colloidal particles and polyelectrolyte can be exploited to obtain surface active species that aid in the formation of emulsions.
Abstract: Hypothesis Albeit solid stabilized emulsions are studied for several decades, the surface of the emulsion drops most often are coated with densely packed and jammed monolayer of particles. However, a control over the area that the particles occupy on the drop surface is necessary, especially in applications involving controlled release of active compounds from emulsions. We hypothesize that it is possible to achieve precise control over the concentration of particles on the surface of emulsions by tailoring the adsorption of different species in a multi-component dispersion used for emulsification. Experiments To this end, we carry out emulsification of oil and aqueous dispersions consisting of a combination of oppositely charged colloidal particles and polyelectrolyte. The droplet size distribution and storage stability of the oil-in-water emulsions, the microstructure, the percentage area of the drop surface occupied by the particles and the adsorption behavior of particle-polyelectrolyte binary dispersions are investigated. Findings Our results demonstrate that the association between oppositely charged colloidal particles and polyelectrolyte can be exploited to obtain surface active species that aid in the formation of emulsions. Moreover, we found that the concentration of particle-polyelectrolyte complexes and polyelectrolyte in the dispersions used in emulsification greatly influence the mean diameter of the emulsions and their microstructure. Our findings provide a strategy to achieve control over surface coverage of particles on the emulsion droplets across a wide range – from a theoretically possible maximum, ≈90%, to as low as ≈5%. Interestingly, the emulsions formulated are found to possess excellent storage stability irrespective of the particle coverage on the drop surface.
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TL;DR: In this article , an approach for formulating porous mullite ceramics from emulsions stabilised by oppositely charged kaolinite and alumina particles is discussed, which can be used as thermal insulator due to low thermal conductivity and tailored microstructure.
Abstract: Clay particles have gained considerable attention as a potential option for stabilising Pickering emulsions in recent years, which are promising templates for the development of porous ceramics intended for high temperature applications. However, the development of porous ceramics using this approach requires control over a number of factors such as stability, microstructure, rheology, and processability of the Pickering emulsions. In this work, we discuss a versatile approach for formulating porous mullite ceramics from emulsions stabilised by oppositely charged kaolinite and alumina particles. In this process, we exploit the electrostatic heteroaggregation phenomena in the oppositely charged mixed colloidal particle system. The aggregates formed by electrostatic interaction readily adsorb to the interface created during emulsification and favor the formation of highly stable Pickering emulsions. The influence of parameters such as concentration of each particle in the mixture, pH, and total particle concentration on the microstructure of Pickering emulsions are studied. We further show that processable Pickering emulsions can be engineered by in-situ surface modification of the hetero-aggregates using a short-chain amphiphile. Porous mullite ceramic is obtained by drying and sintering the optimised emulsion formulation. The phase evolution, microstructure, and porosity of the resulting ceramic are characterised. The macroporous mullite developed through this approach can be used as thermal insulator due to low thermal conductivity and tailored microstructure.
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TL;DR: In this article , the influence of the size and shape of particles and the surface charge of heteroaggregates on the formation of Pickering emulsions and their utilization in the development of porous ceramics is discussed.
Abstract: The aggregation of oppositely charged soft materials (particles, surfactants, polyelectrolytes, etc.) that differ in one or more physical or chemical attributes, broadly referred to as electrostatic heteroaggregation, has been an active area of research for several decades now. While electrostatic heteroaggregation (EHA) is relevant to diverse fields such as environmental engineering, food technology, and pharmaceutical formulations, more recently there has been a resurgence to explore various aspects of this phenomenon in the context of interface stabilization and the development of functional materials. In this Feature Article, we provide an overview of the recent contributions of our group to this exciting field with particular emphasis on fundamental studies of electrostatic heteroaggregation between oppositely charged systems in the bulk, at interfaces, and across the bulk/interface. The influence of the size and shape of particles and the surface charge of heteroaggregates on the formation of Pickering emulsions and their utilization in the development of porous ceramics is discussed.
References
More filters
[...]
TL;DR: The origins, challenges and solutions of NIH Image and ImageJ software are discussed, and how their history can serve to advise and inform other software projects.
Abstract: For the past 25 years NIH Image and ImageJ software have been pioneers as open tools for the analysis of scientific images. We discuss the origins, challenges and solutions of these two programs, and how their history can serve to advise and inform other software projects.
34,063 citations
[...]
TL;DR: In a paper published in Du Bois Reymond's ‘Archiv für Anat. und Physiologie’ in 1894, it was proved that mere agitation of various proteid solutions brought about a separation of some of their contained proteid in the form of fibrous or membrano-fibrous solids, and that it was possible in this way to coagulate and remove the whole of the proteid from solutions of egg-albumin this article.
Abstract: In a paper published in Du Bois Reymond’s ‘Archiv für Anat. und Physiologie’ in 1894, I showed that mere agitation of various proteid solutions brought about a separation of some of their contained proteid in the form of fibrous or membrano-fibrous solids, and that it was possible in this way to coagulate and remove the whole of the proteid from solutions of egg-albumin. It was proved also that these de-solutions and coagulations of proteid were not due to the action of enzymes, heat, or surface evaporation, and were not appreciably affected by the nature of the gas in contact with the liquid or of the vessel in which the agitation was effected. A prolonged series of further experiments, undertaken with a view of ascertaining the precise cause of this phenomenon, has led me to the discovery of an important, but hitherto unnoticed physical fact:—namely, that, quite apart from evaporation, solid or highly viscous coatings are spontaneously, and more or less rapidly formed on the free surfaces of all proteid solutions.
1,096 citations
[...]
TL;DR: In this article, the influence of the wettability of spherical, nanometer-sized silica particles on the type and stability of water−toluene emulsions is described.
Abstract: A systematic investigation into the influence of the wettability of spherical, nanometer-sized silica particles on the type and stability of water−toluene emulsions is described. The particles rang...
1,072 citations
[...]
TL;DR: There is good potential for use of interfacial protein-polysaccharide complexes in the nanoscale engineering of delivery vehicles for nutrient encapsulation and in the protection of adsorbed proteins and emulsified lipids against enzymatic breakdown during digestion.
Abstract: The exploitation of protein–polysaccharide interactions offers opportunities for the design of new ingredients and interfacial structures with applications in the food and pharmaceutical industries. Association of protein and polysaccharide molecules may occur chemically through covalent bonds or physically through electrostatic interactions. Theoretical and experimental studies indicate that various molecular and thermodynamic factors can be adjusted to optimize the effectiveness of covalent conjugates and electrostatic complexes in the stabilization of interfaces, gels and emulsions. Maillard-type protein–polysaccharide conjugates have excellent emulsifying and steric stabilizing properties, especially under conditions where the protein alone is poorly soluble. Charged polysaccharides form soluble complexes or coacervates with proteins depending on pH, ionic strength, and biopolymer charge distribution. The structure and stabilizing properties of the mixed protein + polysaccharide layer depends on the sequence of adsorption of the biopolymers to the interface. There is good potential for use of interfacial protein–polysaccharide complexes in the nanoscale engineering of delivery vehicles for nutrient encapsulation and in the protection of adsorbed proteins and emulsified lipids against enzymatic breakdown during digestion.
438 citations
[...]
TL;DR: A detailed investigation into the behavior of dodecane-water emulsions stabilized by a mixture of silica nanoparticles and pure cationic surfactant has been made, showing that both emulsifiers prefer to stabilize o/w emulsion phase inversion and synergism is displayed in these mixtures.
Abstract: Using a range of complementary experiments, a detailed investigation into the behavior of dodecane-water emulsions stabilized by a mixture of silica nanoparticles and pure cationic surfactant has been made. Both emulsifiers prefer to stabilize o/w emulsions. At high pH, particles are ineffective emulsifiers, whereas surfactant-stabilized emulsions become increasingly stable to coalescence with concentration. In mixtures, no emulsion phase inversion occurs although synergism between the emulsifiers leads to enhanced stability at either fixed surfactant concentration or fixed particle concentration. Emulsions are most stable under conditions where particles have negligible charge and are most flocculated. Freeze fracture scanning electron microscopy confirms the presence of particle flocs at drop interfaces. At low pH, particles and surfactant are good emulsifiers alone. Synergism is also displayed in these mixtures, with the extent of creaming being minimum when particles are most flocculated. Experiments have been undertaken in order to offer an explanation for the latter synergy. By determining the adsorption isotherm of surfactant on particles in water, we show that surfactant addition initially leads to particle flocculation followed by re-dispersion. Using suitable contact angle measurements at oil-water-solid interfaces, we show that silica surfaces initially become increasingly hydrophobic upon surfactant addition, as well as surfactant adsorption lowering the oil-water interfacial tension. A competition exists between the influence of surfactant on the contact angle and the tension in the attachment energy of a particle to the interface.
369 citations
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